To investigate the effects of silicon formulations on the cold tolerance of rice seedlings,Song Japonica 16(not cold tolerant)and Dongnong 427(cold tolerant)rice varieties were used as test materials and four differen...To investigate the effects of silicon formulations on the cold tolerance of rice seedlings,Song Japonica 16(not cold tolerant)and Dongnong 427(cold tolerant)rice varieties were used as test materials and four different types of silicon formulations,Si-50-G,Si-60-G,Si-T-G,and Si-E-G,were applied as foliar sprays at the seedling stage,and a control group CK(equal amount of distilled water)was set up.One week after the first silicon spray,two types of rice were subjected to low-temperature stress treatments at day/night temperatures of 12℃/10℃for 2,4,6,and 8 days.The effects of different silicon formulations on the chlorophyll,proline(Pro)and soluble sugar contents as well as superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT)activities of rice seedlings under low-temperature stress were compared to find out the effects of silicon formulations on the cold tolerance of rice seedlings.The results showed that silicon formulations could significantly increase the chlorophyll content of rice seedling leaves,with Si-50-G being the most effective,with a significant increment of 40.17%compared to the CK at 2 days of low temperature.Four silicon formulations significantly increased the proline content and soluble sugar content of rice leaves at low temperature for 4-8 days.For Song Japonica 16,the most significant increment in leaf POD activity was observed in Si-E-G treatment at 2,4 and 8 days of temperature stress,with 73.58%,20.95%and 217.24%increases compared to the CK,respectively.For 4 and 6 days of temperature stress,the most significant increase in CAT activity was observed in Si-E-G treatment,with 25.70%and 75.78%increases compared to the CK,respectively.For Dongnong 427,the Si-60-G treatment showed the highest increase in leaf SOD activity for 4 and 8 days of temperature stress,with significant increases of 58.15%and 82.76%compared to the CK,respectively,and the Si-E-G treatment showed the highest increase in leaf POD activity for 2 and 8 days of temperature stress,with significant increases of 97.75%and 245.10%compared to the CK,respectively.It showed that the spraying of silicon formulations could significantly enhance the cold tolerance of rice.This study provided a scientific basis for the rational use of silicon formulations to enhance cold tolerance in rice and had important theoretical and practical significance for ensuring sustainable high and stable rice yields in Heilongjiang Province,as well as for the development of silicon fertilizers.展开更多
The process of rice(Oryza sativa L.)seedling cultivation is often subjected to adverse environmental stress.Biostimulants regulate the robust growth of rice seedlings and play a crucial role in promoting the green and...The process of rice(Oryza sativa L.)seedling cultivation is often subjected to adverse environmental stress.Biostimulants regulate the robust growth of rice seedlings and play a crucial role in promoting the green and ecological development of agriculture.In this study,1.0 and 2.0 g•m^(-2) of the biostimulant were applied to soil in rice seedbeds.Growth indicators of rice,antioxidant enzyme activities and soil physicochemical characteristics were assessed at the 2.5-leaf and 4-leaf stages of rice.The results indicated that applying 2.0 g•m^(-2) of the biostimulant at both the 2.5-leaf and 4-leaf stages had the most significant promoting effect on rice growth.At the 2.5-leaf and 4-leaf stages,the number of fibrous roots increased by 23.43%and 22.25%,stem base width increased by 19.05%and 19.58%,above ground dry weight increased by 18.09%and 16.47%,root dry weight increased by 19.67%and 18.28%,leaf peroxidase(POD)activity increased by 34.44%and 42.94%,superoxide dismutase(SOD)activity increased by 37.24%and 56.79%,malondialdehyde(MDA)content decreased by 18.60%and 27.67%,and chlorophyll content increased significantly by 28.31%and 34.24%,respectively.At the 4-leaf stage of rice,urease,phosphatase and cellulase activities in the seedbed soil increased by 42.13%,25.96%and 33.59%,respectively,while soil alkaline nitrogen,available phosphorus and available potassium content decreased by 19.76%,19.02%and 17.88%,respectively.The application of biostimulants played a crucial role in promoting the growth of rice seedlings and enhancing soil nutrient absorption.展开更多
Using early indica rice Zhongzao 39 and japonica rice Xiushui 134 as the experimental materials, the effects of 4 temperature levels after transplantation on turning green, leaf growth, tillering, dry matter accumulat...Using early indica rice Zhongzao 39 and japonica rice Xiushui 134 as the experimental materials, the effects of 4 temperature levels after transplantation on turning green, leaf growth, tillering, dry matter accumulation and nutrition absorption were studied using a greenhouse and an artificial climate chest. We found that (1) tillering did not occur and growth of one new leaf took over 15 days at 16℃. New leaf growth took over 10 days and tillering occurred after 15 days of transplanta- tion at 19 ℃. Tillering appeared 10 days after planting and new leaf growth took 5 days between 22 and 25 ℃. This showed that low temperature impeded the turn- ing green of rice seedlings and the temperature must reach above 19 ℃ to ensure timely appearance of new leaf, tillering and turning green in rice seedlings. (2) When the temperature was 10 increased, both 100-seedling dry weight and nitrogen absorption increased. At temperatures lower 11 than 19 ℃, both dry weight incre- ment and nitrogen absorption were low. Nitrogen absorption of all organs increased obviously between 19 and 22 ℃. Thus, 19 ℃ was found to be an minimum tem- perature for plant organs to absorb nutrients. (3)Tiller of seedling cultivated on dry- land soil and substrate grew quickly and tillering occurred about 7 days after trans- planting. After that, the growth rate was about 0.18 tiller per day. For seedlings cultivated in slurry, tillering occurred 10 days after transplanting and the tillers grew at a rate of 0.16 tiller per day. However, substrate choice during the seedling rais- ing stage had no significant influence on leaf age. (4) Japonica rice exhibited stronger resistance to low temperature than indica rice. Tillering began at about the same time after transplanting in both rice varieties, but japonica rice exhibited higher tillering speed than early indica rice. The speed of leaf growth was higher in japoni- ca rice before transplantation but higher in indica rice after transplantation.展开更多
Two heat-tolerant rice varieties, N5 and TQ, were chosen as test materi- als. Specifically, rice seedlings (leaf age at 2.1), cultivated in room, were treated at 40 ℃ for 7 d and some indices were measured, includi...Two heat-tolerant rice varieties, N5 and TQ, were chosen as test materi- als. Specifically, rice seedlings (leaf age at 2.1), cultivated in room, were treated at 40 ℃ for 7 d and some indices were measured, including plant height, dry weight, leaf color, proline, malondialdehyde and conductivity. The results showed that high temperature advanced the growth of N5 seedlings, for example, plant height, root length and dry weight of ground parts all increased. However, high temperature prevented TQ seedlings growth, plant height in particular. Furthermore, high temper- ature treatment increased the content of chlorophyll of N5 and had none effects on PSII of N5, with little damages on membrane system. On the other hand, high temperature actually reduced PSII activity of TQ, and seriously damaged TQ mem- brane system. It is speculated that the differences of the two varieties lie on pro- duction or removing capacity of reactive oxide species.展开更多
The research used bioassay method to explore seed tolerance of Cd in terms of seed germination and seedling growth. Specifically, 12 rice varieties of three types were investigated under Cd stress, covering germinatio...The research used bioassay method to explore seed tolerance of Cd in terms of seed germination and seedling growth. Specifically, 12 rice varieties of three types were investigated under Cd stress, covering germination rate, shooting index, vigor index, seedling and shoot lengths, and fresh weights. The results showed that as Cd concentration grew, seed germination and seedling growth kept increasingly inhibited; germination index, vigor index, root length, shoot length and fresh weights went down; inhibition effects on seed germination and seedling growth were conventional rice〉two-line hybrid rice〉three-line hybrid ,rice. Shanyou 9588, Tianyou 998, Chuanxiang 8, and Y Liangyou 1 performed ~rongly in Cd tolerance; C Liangyou 651, Nei 5 You 263, Xiangwanxian 16, Huanghuazhan, Xiangwanxian 13, and Zhunliangyou 527 performed poorly in Cd tolerance, and Cd tolerance of rest treatments were moderate.展开更多
[Objective] This study was conducted to discuss influence factors for safety full heading of machine-transplanted rice seedlings in cool-warm rice area. [Method] Effects of variety, seedling age and nitrogen fertilize...[Objective] This study was conducted to discuss influence factors for safety full heading of machine-transplanted rice seedlings in cool-warm rice area. [Method] Effects of variety, seedling age and nitrogen fertilizer dosage and strategy of machine-transplanted seedlings on safety full heading of machine-transplanted seedlings were investigated. [Result] During mechanized rice production in coolwarm rice area, mid-early-maturing cold-resistant varieties with growth periods no longer than 180 d could selected, and seedling age could controlled within 30-35 d; and the total amount of pure nitrogen should be less than 300 kg/hm^2, and the proportion of nitrogen fertilizer applied in later stages should be properly reduced. [Conclusion] Under this condition, safety full heading of rice is ensured, and the target yield is realized.展开更多
[Objective] With a rice variety "Long Rice 11" as a test cultivar,an experiment of raising rice seedlings with the new substrata prepared from biochar,and maize stalks,rice husks,organic fertilizer,turf,zeolite,fine...[Objective] With a rice variety "Long Rice 11" as a test cultivar,an experiment of raising rice seedlings with the new substrata prepared from biochar,and maize stalks,rice husks,organic fertilizer,turf,zeolite,fine river sand and arable layer soil by mixing according to certain volume proportions was caried out,in order to investigate the physical and chemical properties of different organic-material seedling-raising substrata and the effects of these substrata on seedling growth.[Method] The experiment raised seedlings in greenhouses and adopted randomized block arrangement.[Result] The substratum of biochar mixed with maize stalks and rice husks could increase the maximum water-holding capacity of the substratum,reduce the volume weight of the substratum and improve the buffering effect of the substratum.It also had great effects on the contents of alkali-hydrolyzale nitrogen and rapidly available potassium in the substratum,and could improve the root number and substantial degree of rice seedlings.[Conclusion] Biochar with maize stalks and rice husks(the treament HC) is the optimal substratum in this study.展开更多
This study was conducted to investigate the effects of bast fiber seedling film on rice seedling growth. In this study, indica cultivar 'Xiangwanxian 13' and indica hybrid cuitivar 'Y Liangyou 1' were used to inve...This study was conducted to investigate the effects of bast fiber seedling film on rice seedling growth. In this study, indica cultivar 'Xiangwanxian 13' and indica hybrid cuitivar 'Y Liangyou 1' were used to investigate the changes of aboveground part growth and root respiration enzyme activities of rice seedlings af- ter the application of bast fiber seedling film. The results showed that, compared with the CK, the accumulation of shoot biomass, chlorophyll content, root bleeding intensity, soluble sugar content, and nitrate nitrogen content were significantly im- proved with the application of bast fiber seedling film. In addition, the activities of malate dehydrogenas (MDH) and alcohol dehydrogenas (ADH) were higher in rice seedling roots raised with bast fiber seedling film, while there was no significant change in lactate dehydrogenase (LDH) after the application of bast fiber seedling film. However, there were no significant differences in these indexes between the two cultivars. All the results indicated that the growth and development of rice seedlings could be improved with the application of bast fiber seedling film.展开更多
Soil salinity seriously affects the utilization of farmland and threatens the crop production.Here,a selenium-nitrogen-co-doped carbon dots was developed,which increased rice seedling growth and alleviated its inhibit...Soil salinity seriously affects the utilization of farmland and threatens the crop production.Here,a selenium-nitrogen-co-doped carbon dots was developed,which increased rice seedling growth and alleviated its inhibition by salt stress by foliar spraying.The treatment activated Ca^(2+)and jasmonic acid signaling pathways and increased iron homeostasis,antioxidant defense,and cell wall development of rice seedlings.It could be used to increase crop resistance to environmental stress.展开更多
Phosphorus (P) deficiency is thought to exacerbate the arsenic (As) phytotoxicity in paddy rice. The experiments were conducted to investigate the effects of external phosphate supply on As accumulation in rice an...Phosphorus (P) deficiency is thought to exacerbate the arsenic (As) phytotoxicity in paddy rice. The experiments were conducted to investigate the effects of external phosphate supply on As accumulation in rice and its toxicity under phosphate deficiency conditions. Rice seedlings pretreated with a phosphorus deficient nutrient solution (-P) for 14 d accumulated more As than those pretreated with a normal phosphorus supply nutrient solution (+P). Rice protreated with -P showed As toxicity symptoms after being exposed to 50 μmol/L arsenate for 4 h, while +P rice did not show any toxicity symptoms. Arsenic toxicity symptoms can be alleviated by increasing external P concentrations. The arsenate uptake rate and accumulation corresponded with the As toxicity in rice plants. Arsenic concentrations in rice roots decreased with increasing external phosphate concentrations. The lowest As accumulation and the highest P accumulation were found when the external P concentration reached 100μmol/L. In short, P deficiency increased the sensitivity of rice to arsenate and increasing of external phosphate supply could alleviate As toxicity.展开更多
Two indica rice (Oryza sativa L.) materials, Xieqingzao B (sensitive to heat stress) and 082 (tolerant to heat stress) were used to study the role of brassinolide (BR) in protection of rice seedlings from heat...Two indica rice (Oryza sativa L.) materials, Xieqingzao B (sensitive to heat stress) and 082 (tolerant to heat stress) were used to study the role of brassinolide (BR) in protection of rice seedlings from heat stress. Young seedlings were subjected to high temperature (38℃/30℃) and sprayed with 0.005 mg/L of BR. Analysis was conducted on the contents of chlorophyll, protein and malondialdehyde (MDA), the leakage of electrolyte, the activities of peroxidase (POD) and superoxide dismutase (SOD) and their isozymes expression levels in leaves. Under the high temperature treatment, application of BR significantly increased the contents of chlorophyll and protein, and the activities of POD and SOD, and reduced the content of MDA and the leakage of electrolyte in the leaves of the heat-sensitive material Xieqingzao B, whereas BR had less effect on those of the heat-tolerant material 082 relatively. The BR treatment enhanced the expression of POD isozymes in the leaves of both materials. Under the high temperature stress and BR treatment, the expression of four SOD isozymes reduced in 082, but the expression of two SOD isozymes increased in Xieqingzao B. This suggests that BR plays an important role in protection of rice seedlings from heat stress by enhancing the activities or expression level of protective enzymes in the leaves. The materials with various heat-tolerance might differ in the mechanism of response to heat stress with BR application.展开更多
Studies were initiated for two consecutive years to find out the effect of time of transplanting and seedlings hill^-l on the productivity of rice in Dera Ismail Khan district of North West Frontier Province (NWFP),...Studies were initiated for two consecutive years to find out the effect of time of transplanting and seedlings hill^-l on the productivity of rice in Dera Ismail Khan district of North West Frontier Province (NWFP), Pakistan. The experiment was laid out in a randomized complete block design with split plot arrangements. Main plots consisted of four transplanting dates viz. 20th and 27th of June and 4th and 1 lth of July while sub-plots contained 1, 2, 3 or 4 seedlings hill^-1. Among transplanting dates, June 20th planted crop gave highest paddy yield and net return with I seedling hill^-1. It explains that the use of more seedlings hill^-1 not only adds to cost but is also a mere wastage of natural resources. Based on research findings, we conclude that the use of I seedling hill^-1 is most appropriate for timely sowing otherwise 4 seedlings hill^-1 should be used to compensate for the yield gap in late transplanted rice.展开更多
The dry-raised seedlings (D-RS)of rice had obvious superiority in tillering and growth after transplanting. Especially under the condition of water-saving irrigation or low soil moisture, D-RS had more productive till...The dry-raised seedlings (D-RS)of rice had obvious superiority in tillering and growth after transplanting. Especially under the condition of water-saving irrigation or low soil moisture, D-RS had more productive tillers, higher dry matter accumulation, larger grain-filling rate, slower senescence of leaves and stronger root activity during ripening, and higher grain yield, compared with the moist-raised seedlings (MRS). D-RS had smaller yield reduction than M-RS when subject to heavy water stress. The results suggested that D-RS had the ability to adapt to lower soil moisture in paddy field. Basedon the response of D-RS to soil moisture at each growth stage, the water-saving and high-yielding irrigation indices through controlling lowlimit soil water potential were proposed, i.e. soil water potential was - 15 - - 20 kPa from the recovery to the criticalleaf-age of productive tillering, - 20 - - 40 kPa from the critical leaf-age of productive tillering to secondary branch-differentiating stage, - 15 - - 25 kPa from secondary branch-differentiating stage to 20 days after heading and - 25 - - 35 kPa from 21 to 45 days after heading.展开更多
Understanding the characteristics of rice productivity is of great importance for achieving high yield formation.However,such traits have not yet been studied for different ages of hydroponically grown long-mat rice s...Understanding the characteristics of rice productivity is of great importance for achieving high yield formation.However,such traits have not yet been studied for different ages of hydroponically grown long-mat rice seedlings(HLMS),which constitutes a new method of seedling cultivation.Field experiments were conducted to evaluate the effects of seedling age on the growth stage,photosynthesis characteristics,dry matter production,and yield of HLMS.A conventional japonica rice cultivar(Wuyunjing 24)and an indica hybrid rice cultivar(6 Liangyou 9368)were used as test materials.The results showed that the whole phase was shortened by 13-15 days for young seedlings(13-day-old)compared with old seedlings(27-day-old),which occurred because the growth process accelerated with the transplantation of young seedlings.As seedling age increased,the dry matter weight of stems of individual plants and of the population increased at the transplanting stage but decreased at the maturity stage(MS).Compared with that of 27-day-old seedlings,the average ratio of panicle weight to total plant dry weight of 13-day-old seedlings during a 2-year period increased by 3.71%for Wuyunjing 24 and by 3.78%for 6 Liangyou 9368 at the MS.Moreover,as seedling age increased,the leaf area index and photosynthetic potential decreased for both cultivars,and the photosynthetic rate markedly decreased at the heading stage(HS).With the exception of that of Wuyunjing 24 from the jointing stage to the HS in 2014,the crop growth rate was higher for young seedlings than for old seedlings.Grain yield significantly decreased with seedling age,but no significant difference was detected between the 13-and 20-day-old seedlings for either cultivar.Therefore,equilibrious and high biological yield formation,vigorous growth in the late stages,and high photosynthetic production capacity are important characteristics and causes of the efficient and sustainable output of photosynthetic systems and for achieving high yield formation in young transplanted seedlings(13-20-day-old).展开更多
In rice, OsABA8ox encodes abscisic acid(ABA) 8′-hydroxylase, which catalyzes the committed step of ABA catabolism. The contribution of ABA catabolism in root development remains unclear. We investigated the role of O...In rice, OsABA8ox encodes abscisic acid(ABA) 8′-hydroxylase, which catalyzes the committed step of ABA catabolism. The contribution of ABA catabolism in root development remains unclear. We investigated the role of OsABA8ox2 in root growth and development and drought response. GUS staining results showed that OsABA8ox2 was expressed mainly in roots at seedling stage and was strongly expressed in the meristematic zone of the radicle. OsABA8ox2 expression in roots was markedly decreased after 0.5 h polyethylene glycol(PEG) treatment and increased after 0.5 h rehydration, implying that OsABA8ox2 is a drought-responsive gene.OsABA8ox2 knockout mediated by the CRISPR-Cas9 system increased drought-induced ABA and indole-3-acetic acid accumulation in roots, conferred increased ABA sensitivity, and promoted a more vertically oriented root system architecture(RSA) beneficial to drought tolerance.OsABA8ox2 overexpression suppressed root elongation and increased stomatal conductance and transpiration rate. Consequently, OsABA8ox2 knockout dramatically improved rice drought tolerance, whereas OsABA8ox2 overexpression seedlings were hypersensitive to drought stress,suggesting that OsABA8ox2 contributes to drought response in rice. Compared with wild type,functional leaves of OsABA8ox2 knockout seedlings showed higher ABA levels, whereas overexpression lines showed lower ABA levels, suggesting that OsABA8ox2, as an ABA catabolic gene, modulates ABA concentration through ABA catabolism. OsABA8ox2 and OsABA8ox3 were both localized in the endoplasmic reticulum. Together, these results indicate that OsABA8ox2 suppresses root elongation of rice seedlings, increases water transpiration, and contributes to drought response through ABA catabolism, and that OsABA8ox2 knockout dramatically improves rice drought tolerance. They highlight the key role of ABA catabolism mediated by OsABA8ox2 on root growth and development. OsABA8ox2, as a novel RSA gene, would be a potential genetic target for the improvement of rice drought tolerance.展开更多
The seedlings of 6 rice varieties were treated with Cd concentrations of 25,50 and 100μmol/L for 5 d.The results showed that the longest root length,seedling height,fresh weight per plant and dry weight per plant of ...The seedlings of 6 rice varieties were treated with Cd concentrations of 25,50 and 100μmol/L for 5 d.The results showed that the longest root length,seedling height,fresh weight per plant and dry weight per plant of 6 rice varieties were significantly inhibited.The inhibiting effects showed a trend as the following:the longest root length>fresh weight per plant>dry weight per plant>seedling height,and the inhibiting effect increased with the increase of Cd stress concentration.It is more economical and reasonable to use 50μmol/L Cd stress concentration to identify Cd tolerance of rice seedlings.And it is more scienti fic to evaluate the Cd tolerance of rice seedling comprehensively by using the 4 indexes of longest root length,fresh weight per plant,dry weight per plant and seedling height.展开更多
The traditional soil-based rice seedling production methods for mechanical transplanting are resource-intensive,time consuming and laborious.The improvement and optimization of nutrient management in soil-less nursery...The traditional soil-based rice seedling production methods for mechanical transplanting are resource-intensive,time consuming and laborious.The improvement and optimization of nutrient management in soil-less nursery raising methods like tandem long-mat seedlings(TLMS)are necessary for the resource-efficient cultivation of rice.In the present study,a controlled-release fertilizer(CRF)-polymer-coated compound fertilizer with 3 months release period(PCCF-3M)was applied as seedling fertilizer(SF),and five different dosages of SF(SF-0,SF-10,SF-20,SF-30,and SF-40)were compared with an organic substrate as the control(CK).Among all SF treatments,the best results were obtained with the application of 20 g/tray of SF(SF-20),as the seedling quality and machine transplanting quality were comparable to those of CK.In contrast,the lower dosages(SF-0 and SF-10)resulted in low nitrogen content and reduced shoot growth,while the higher dosages(SF-30 and SF-40)resulted in toxicity(increased malondialdehyde accumulation)and inhibited the root growth.Similarly,SF-20 increased panicle number(5.6-7.0%)and yield(4.3-5.3%)compared with CK,which might be related to the remaining SF entangled in the roots supporting the tiller growth of rice seedlings in the field.Moreover,SF-20 reduced the seedling block weight(53.1%)and cost of seedling production(23.5%)but increased the gross margin,indicating that it was easy to handle and economical.Taken together,our results indicate that SF-20 is a cost-effective way to promote the growth and transplanting efficiency of rice seedlings.To our knowledge,this study is the first to determine the optimum dosage of CRF for the soil-less production of rice seedlings.展开更多
This study was conducted to determine whether,and if so how,the grain yield and nitrogen(N) requirements of hybrid rice transplanted as single seedlings are affected by no-tillage(NT) practices.A fixed field experimen...This study was conducted to determine whether,and if so how,the grain yield and nitrogen(N) requirements of hybrid rice transplanted as single seedlings are affected by no-tillage(NT) practices.A fixed field experiment was done at the Experimental Farm of Hunan Agricultural University in Changsha,Hunan Province,China,from 2004 to 2014.Grain yield and yield attributes(panicle number per m2,spikelet number per panicle,spikelet filling percentage,grain weight,total biomass,and harvest index) were evaluated as well as the N-use characteristics(total N uptake,internal N-use efficiency,and N requirements) of hybrid rice transplanted as single seedlings comparing NT with conventional tillage(CT).A significant finding was that there were no significant differences in grain yield,yield attributes,and N-use characteristics between CT and NT.Averaged across the 11 years,grain yield and N requirements were 9.51 t ha^(-1) and 20.2 kg t^(-1) under CT and 9.33 t ha^(-1) and 20.0 kg t^(-1) under NT,respectively.There were significant yearly variations in grain yield,yield attributes,and N-use characteristics observed under both CT and NT.The yearly variation in grain yield was related to simultaneous changes in spikelet number per panicle,grain weight,total biomass,and harvest index.Also,it was found that grain yield was positively correlated with internal N-use efficiency but negatively correlated with N requirements.It is concluded that grain yield and N requirements in hybrid rice when transplanted as single seedlings are not affected adversely by NT.The results of this study suggest that(1) compatible relationships among yield attributes can be established in hybrid rice that is transplanted as single seedlings,and(2) higher grain yield and higher N-use efficiency can be concurrently achieved in hybrid rice transplanted as single seedlings.展开更多
Xanthine dehydrogenase(XDH) is a crucial enzyme involved in purine metabolism. To evaluate the effect of XDH deficiency on rice growth during dark treatment, wild type(WT) Nipponbare(Oryza sativa L.) and two independe...Xanthine dehydrogenase(XDH) is a crucial enzyme involved in purine metabolism. To evaluate the effect of XDH deficiency on rice growth during dark treatment, wild type(WT) Nipponbare(Oryza sativa L.) and two independent transgenic lines with severe RNAi suppression(xdh3 and xdh4) were used in the present experiment. Under normal growth conditions, chlorophyll levels and biomass were indistinguishable between WT and the two RNAi transgenic lines, but XDH enzyme activity and ureide levels were suppressed in XDH RNAi transgenic lines. When XDH RNAi transgenic lines were subjected to dark treatment, chlorophyll content and biomass were significantly decreased, while O~–· production rate and malonaldehyde(MDA) were significantly increased compared to WT. The spraying test of exogenous allantoin raised chlorophyll content and biomass and reduced O~–· production rate and MDA in WT and both transgenic lines, and it also simultaneously reduced differences between RNAi and WT plants caused by XDH deficiency in growth potential and anti-oxidative capacity under dark treatment. These results suggested that fully functional purine metabolism plays an important role in reducing the sensitivity of rice seedlings to dark stress.展开更多
基金the National Natural Science Foundation of China(31471440)。
文摘To investigate the effects of silicon formulations on the cold tolerance of rice seedlings,Song Japonica 16(not cold tolerant)and Dongnong 427(cold tolerant)rice varieties were used as test materials and four different types of silicon formulations,Si-50-G,Si-60-G,Si-T-G,and Si-E-G,were applied as foliar sprays at the seedling stage,and a control group CK(equal amount of distilled water)was set up.One week after the first silicon spray,two types of rice were subjected to low-temperature stress treatments at day/night temperatures of 12℃/10℃for 2,4,6,and 8 days.The effects of different silicon formulations on the chlorophyll,proline(Pro)and soluble sugar contents as well as superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT)activities of rice seedlings under low-temperature stress were compared to find out the effects of silicon formulations on the cold tolerance of rice seedlings.The results showed that silicon formulations could significantly increase the chlorophyll content of rice seedling leaves,with Si-50-G being the most effective,with a significant increment of 40.17%compared to the CK at 2 days of low temperature.Four silicon formulations significantly increased the proline content and soluble sugar content of rice leaves at low temperature for 4-8 days.For Song Japonica 16,the most significant increment in leaf POD activity was observed in Si-E-G treatment at 2,4 and 8 days of temperature stress,with 73.58%,20.95%and 217.24%increases compared to the CK,respectively.For 4 and 6 days of temperature stress,the most significant increase in CAT activity was observed in Si-E-G treatment,with 25.70%and 75.78%increases compared to the CK,respectively.For Dongnong 427,the Si-60-G treatment showed the highest increase in leaf SOD activity for 4 and 8 days of temperature stress,with significant increases of 58.15%and 82.76%compared to the CK,respectively,and the Si-E-G treatment showed the highest increase in leaf POD activity for 2 and 8 days of temperature stress,with significant increases of 97.75%and 245.10%compared to the CK,respectively.It showed that the spraying of silicon formulations could significantly enhance the cold tolerance of rice.This study provided a scientific basis for the rational use of silicon formulations to enhance cold tolerance in rice and had important theoretical and practical significance for ensuring sustainable high and stable rice yields in Heilongjiang Province,as well as for the development of silicon fertilizers.
文摘The process of rice(Oryza sativa L.)seedling cultivation is often subjected to adverse environmental stress.Biostimulants regulate the robust growth of rice seedlings and play a crucial role in promoting the green and ecological development of agriculture.In this study,1.0 and 2.0 g•m^(-2) of the biostimulant were applied to soil in rice seedbeds.Growth indicators of rice,antioxidant enzyme activities and soil physicochemical characteristics were assessed at the 2.5-leaf and 4-leaf stages of rice.The results indicated that applying 2.0 g•m^(-2) of the biostimulant at both the 2.5-leaf and 4-leaf stages had the most significant promoting effect on rice growth.At the 2.5-leaf and 4-leaf stages,the number of fibrous roots increased by 23.43%and 22.25%,stem base width increased by 19.05%and 19.58%,above ground dry weight increased by 18.09%and 16.47%,root dry weight increased by 19.67%and 18.28%,leaf peroxidase(POD)activity increased by 34.44%and 42.94%,superoxide dismutase(SOD)activity increased by 37.24%and 56.79%,malondialdehyde(MDA)content decreased by 18.60%and 27.67%,and chlorophyll content increased significantly by 28.31%and 34.24%,respectively.At the 4-leaf stage of rice,urease,phosphatase and cellulase activities in the seedbed soil increased by 42.13%,25.96%and 33.59%,respectively,while soil alkaline nitrogen,available phosphorus and available potassium content decreased by 19.76%,19.02%and 17.88%,respectively.The application of biostimulants played a crucial role in promoting the growth of rice seedlings and enhancing soil nutrient absorption.
基金Supported by Special Scientific Research Funds for Commonweal Section(Agriculture)(201203029,201003016)China Rice Industry System Project(2011-2015)Special Funding for Basic Scientific Research and Zhejiang Provincial Natural Science Foundation(LY13C130004)~~
文摘Using early indica rice Zhongzao 39 and japonica rice Xiushui 134 as the experimental materials, the effects of 4 temperature levels after transplantation on turning green, leaf growth, tillering, dry matter accumulation and nutrition absorption were studied using a greenhouse and an artificial climate chest. We found that (1) tillering did not occur and growth of one new leaf took over 15 days at 16℃. New leaf growth took over 10 days and tillering occurred after 15 days of transplanta- tion at 19 ℃. Tillering appeared 10 days after planting and new leaf growth took 5 days between 22 and 25 ℃. This showed that low temperature impeded the turn- ing green of rice seedlings and the temperature must reach above 19 ℃ to ensure timely appearance of new leaf, tillering and turning green in rice seedlings. (2) When the temperature was 10 increased, both 100-seedling dry weight and nitrogen absorption increased. At temperatures lower 11 than 19 ℃, both dry weight incre- ment and nitrogen absorption were low. Nitrogen absorption of all organs increased obviously between 19 and 22 ℃. Thus, 19 ℃ was found to be an minimum tem- perature for plant organs to absorb nutrients. (3)Tiller of seedling cultivated on dry- land soil and substrate grew quickly and tillering occurred about 7 days after trans- planting. After that, the growth rate was about 0.18 tiller per day. For seedlings cultivated in slurry, tillering occurred 10 days after transplanting and the tillers grew at a rate of 0.16 tiller per day. However, substrate choice during the seedling rais- ing stage had no significant influence on leaf age. (4) Japonica rice exhibited stronger resistance to low temperature than indica rice. Tillering began at about the same time after transplanting in both rice varieties, but japonica rice exhibited higher tillering speed than early indica rice. The speed of leaf growth was higher in japoni- ca rice before transplantation but higher in indica rice after transplantation.
基金Supported by National Natural Science Foundation of China(30771156,31200387)~~
文摘Two heat-tolerant rice varieties, N5 and TQ, were chosen as test materi- als. Specifically, rice seedlings (leaf age at 2.1), cultivated in room, were treated at 40 ℃ for 7 d and some indices were measured, including plant height, dry weight, leaf color, proline, malondialdehyde and conductivity. The results showed that high temperature advanced the growth of N5 seedlings, for example, plant height, root length and dry weight of ground parts all increased. However, high temperature prevented TQ seedlings growth, plant height in particular. Furthermore, high temper- ature treatment increased the content of chlorophyll of N5 and had none effects on PSII of N5, with little damages on membrane system. On the other hand, high temperature actually reduced PSII activity of TQ, and seriously damaged TQ mem- brane system. It is speculated that the differences of the two varieties lie on pro- duction or removing capacity of reactive oxide species.
基金Supported by Loudi City Science and Technology Project(2014-1)State Key Laboratory of Hybrid RiceKey Laboratory of Pesticide Harmless Application of Hunan Province~~
文摘The research used bioassay method to explore seed tolerance of Cd in terms of seed germination and seedling growth. Specifically, 12 rice varieties of three types were investigated under Cd stress, covering germination rate, shooting index, vigor index, seedling and shoot lengths, and fresh weights. The results showed that as Cd concentration grew, seed germination and seedling growth kept increasingly inhibited; germination index, vigor index, root length, shoot length and fresh weights went down; inhibition effects on seed germination and seedling growth were conventional rice〉two-line hybrid rice〉three-line hybrid ,rice. Shanyou 9588, Tianyou 998, Chuanxiang 8, and Y Liangyou 1 performed ~rongly in Cd tolerance; C Liangyou 651, Nei 5 You 263, Xiangwanxian 16, Huanghuazhan, Xiangwanxian 13, and Zhunliangyou 527 performed poorly in Cd tolerance, and Cd tolerance of rest treatments were moderate.
文摘[Objective] This study was conducted to discuss influence factors for safety full heading of machine-transplanted rice seedlings in cool-warm rice area. [Method] Effects of variety, seedling age and nitrogen fertilizer dosage and strategy of machine-transplanted seedlings on safety full heading of machine-transplanted seedlings were investigated. [Result] During mechanized rice production in coolwarm rice area, mid-early-maturing cold-resistant varieties with growth periods no longer than 180 d could selected, and seedling age could controlled within 30-35 d; and the total amount of pure nitrogen should be less than 300 kg/hm^2, and the proportion of nitrogen fertilizer applied in later stages should be properly reduced. [Conclusion] Under this condition, safety full heading of rice is ensured, and the target yield is realized.
文摘[Objective] With a rice variety "Long Rice 11" as a test cultivar,an experiment of raising rice seedlings with the new substrata prepared from biochar,and maize stalks,rice husks,organic fertilizer,turf,zeolite,fine river sand and arable layer soil by mixing according to certain volume proportions was caried out,in order to investigate the physical and chemical properties of different organic-material seedling-raising substrata and the effects of these substrata on seedling growth.[Method] The experiment raised seedlings in greenhouses and adopted randomized block arrangement.[Result] The substratum of biochar mixed with maize stalks and rice husks could increase the maximum water-holding capacity of the substratum,reduce the volume weight of the substratum and improve the buffering effect of the substratum.It also had great effects on the contents of alkali-hydrolyzale nitrogen and rapidly available potassium in the substratum,and could improve the root number and substantial degree of rice seedlings.[Conclusion] Biochar with maize stalks and rice husks(the treament HC) is the optimal substratum in this study.
基金Supported by Scientific and Technological Innovation Project of Chinese Academy of Agricultural Sciences(ASTIP-IBFC07)Production Post of Degradable Bast Fiber Mulching Film of National Agro-Industry Technology Research System for Bast and Leaf Fiber Crops(CARS-19-E23)~~
文摘This study was conducted to investigate the effects of bast fiber seedling film on rice seedling growth. In this study, indica cultivar 'Xiangwanxian 13' and indica hybrid cuitivar 'Y Liangyou 1' were used to investigate the changes of aboveground part growth and root respiration enzyme activities of rice seedlings af- ter the application of bast fiber seedling film. The results showed that, compared with the CK, the accumulation of shoot biomass, chlorophyll content, root bleeding intensity, soluble sugar content, and nitrate nitrogen content were significantly im- proved with the application of bast fiber seedling film. In addition, the activities of malate dehydrogenas (MDH) and alcohol dehydrogenas (ADH) were higher in rice seedling roots raised with bast fiber seedling film, while there was no significant change in lactate dehydrogenase (LDH) after the application of bast fiber seedling film. However, there were no significant differences in these indexes between the two cultivars. All the results indicated that the growth and development of rice seedlings could be improved with the application of bast fiber seedling film.
基金financially supported by the National Natural Science Foundation of China (42207032,52070064)the Key Project of National Natural Science Foundation of China (42330705)+2 种基金Key R&D Project of Hebei Province (21373601D)Advanced Talents Incubation Program of the Hebei University (521100222012)economic support from Collaborative Innovation Center for Baiyangdian Basin Ecological Protection and Beijing-Tianjin-Hebei Sustainable Development and Institute of Life Sciences and Green Development of Hebei University。
文摘Soil salinity seriously affects the utilization of farmland and threatens the crop production.Here,a selenium-nitrogen-co-doped carbon dots was developed,which increased rice seedling growth and alleviated its inhibition by salt stress by foliar spraying.The treatment activated Ca^(2+)and jasmonic acid signaling pathways and increased iron homeostasis,antioxidant defense,and cell wall development of rice seedlings.It could be used to increase crop resistance to environmental stress.
基金supported by the National Natural Sci-ence Foundation of China (No. 40671102, 20777083)the Knowledge Innovation Program of the Chinese Academy of Sciences (No. RCEES-QN-200702)the Special Funds for Young Scholars of RCEES, CAS
文摘Phosphorus (P) deficiency is thought to exacerbate the arsenic (As) phytotoxicity in paddy rice. The experiments were conducted to investigate the effects of external phosphate supply on As accumulation in rice and its toxicity under phosphate deficiency conditions. Rice seedlings pretreated with a phosphorus deficient nutrient solution (-P) for 14 d accumulated more As than those pretreated with a normal phosphorus supply nutrient solution (+P). Rice protreated with -P showed As toxicity symptoms after being exposed to 50 μmol/L arsenate for 4 h, while +P rice did not show any toxicity symptoms. Arsenic toxicity symptoms can be alleviated by increasing external P concentrations. The arsenate uptake rate and accumulation corresponded with the As toxicity in rice plants. Arsenic concentrations in rice roots decreased with increasing external phosphate concentrations. The lowest As accumulation and the highest P accumulation were found when the external P concentration reached 100μmol/L. In short, P deficiency increased the sensitivity of rice to arsenate and increasing of external phosphate supply could alleviate As toxicity.
基金This work was supported by the National Natural Science Foundation(Grant No.30671225)the Natural Science Foundation of Jiangsu Province(Grant No.BK2006069)Nantong University School Program(Grant No.06Z108).
文摘Two indica rice (Oryza sativa L.) materials, Xieqingzao B (sensitive to heat stress) and 082 (tolerant to heat stress) were used to study the role of brassinolide (BR) in protection of rice seedlings from heat stress. Young seedlings were subjected to high temperature (38℃/30℃) and sprayed with 0.005 mg/L of BR. Analysis was conducted on the contents of chlorophyll, protein and malondialdehyde (MDA), the leakage of electrolyte, the activities of peroxidase (POD) and superoxide dismutase (SOD) and their isozymes expression levels in leaves. Under the high temperature treatment, application of BR significantly increased the contents of chlorophyll and protein, and the activities of POD and SOD, and reduced the content of MDA and the leakage of electrolyte in the leaves of the heat-sensitive material Xieqingzao B, whereas BR had less effect on those of the heat-tolerant material 082 relatively. The BR treatment enhanced the expression of POD isozymes in the leaves of both materials. Under the high temperature stress and BR treatment, the expression of four SOD isozymes reduced in 082, but the expression of two SOD isozymes increased in Xieqingzao B. This suggests that BR plays an important role in protection of rice seedlings from heat stress by enhancing the activities or expression level of protective enzymes in the leaves. The materials with various heat-tolerance might differ in the mechanism of response to heat stress with BR application.
文摘Studies were initiated for two consecutive years to find out the effect of time of transplanting and seedlings hill^-l on the productivity of rice in Dera Ismail Khan district of North West Frontier Province (NWFP), Pakistan. The experiment was laid out in a randomized complete block design with split plot arrangements. Main plots consisted of four transplanting dates viz. 20th and 27th of June and 4th and 1 lth of July while sub-plots contained 1, 2, 3 or 4 seedlings hill^-1. Among transplanting dates, June 20th planted crop gave highest paddy yield and net return with I seedling hill^-1. It explains that the use of more seedlings hill^-1 not only adds to cost but is also a mere wastage of natural resources. Based on research findings, we conclude that the use of I seedling hill^-1 is most appropriate for timely sowing otherwise 4 seedlings hill^-1 should be used to compensate for the yield gap in late transplanted rice.
文摘The dry-raised seedlings (D-RS)of rice had obvious superiority in tillering and growth after transplanting. Especially under the condition of water-saving irrigation or low soil moisture, D-RS had more productive tillers, higher dry matter accumulation, larger grain-filling rate, slower senescence of leaves and stronger root activity during ripening, and higher grain yield, compared with the moist-raised seedlings (MRS). D-RS had smaller yield reduction than M-RS when subject to heavy water stress. The results suggested that D-RS had the ability to adapt to lower soil moisture in paddy field. Basedon the response of D-RS to soil moisture at each growth stage, the water-saving and high-yielding irrigation indices through controlling lowlimit soil water potential were proposed, i.e. soil water potential was - 15 - - 20 kPa from the recovery to the criticalleaf-age of productive tillering, - 20 - - 40 kPa from the critical leaf-age of productive tillering to secondary branch-differentiating stage, - 15 - - 25 kPa from secondary branch-differentiating stage to 20 days after heading and - 25 - - 35 kPa from 21 to 45 days after heading.
基金Funding was provided by the National Key Research and Development Program of China(2017YFD0301200,2018YFD0300803,2015BAD01B03)the Jiangsu Key Research and Development Program,China(BE2017369)the Jiangsu Agricultural Science and Technology Innovation Fund,China(JASTIF,CX(18)1002).
文摘Understanding the characteristics of rice productivity is of great importance for achieving high yield formation.However,such traits have not yet been studied for different ages of hydroponically grown long-mat rice seedlings(HLMS),which constitutes a new method of seedling cultivation.Field experiments were conducted to evaluate the effects of seedling age on the growth stage,photosynthesis characteristics,dry matter production,and yield of HLMS.A conventional japonica rice cultivar(Wuyunjing 24)and an indica hybrid rice cultivar(6 Liangyou 9368)were used as test materials.The results showed that the whole phase was shortened by 13-15 days for young seedlings(13-day-old)compared with old seedlings(27-day-old),which occurred because the growth process accelerated with the transplantation of young seedlings.As seedling age increased,the dry matter weight of stems of individual plants and of the population increased at the transplanting stage but decreased at the maturity stage(MS).Compared with that of 27-day-old seedlings,the average ratio of panicle weight to total plant dry weight of 13-day-old seedlings during a 2-year period increased by 3.71%for Wuyunjing 24 and by 3.78%for 6 Liangyou 9368 at the MS.Moreover,as seedling age increased,the leaf area index and photosynthetic potential decreased for both cultivars,and the photosynthetic rate markedly decreased at the heading stage(HS).With the exception of that of Wuyunjing 24 from the jointing stage to the HS in 2014,the crop growth rate was higher for young seedlings than for old seedlings.Grain yield significantly decreased with seedling age,but no significant difference was detected between the 13-and 20-day-old seedlings for either cultivar.Therefore,equilibrious and high biological yield formation,vigorous growth in the late stages,and high photosynthetic production capacity are important characteristics and causes of the efficient and sustainable output of photosynthetic systems and for achieving high yield formation in young transplanted seedlings(13-20-day-old).
基金supported by the National Natural Science Foundation of China(31501244)Chinese Academy of Agricultural Sciences Elite Youth Program Grant to Yubin Lithe Fundamental Research Funds for Central Non-profit Scientific Institution(1610392019001)。
文摘In rice, OsABA8ox encodes abscisic acid(ABA) 8′-hydroxylase, which catalyzes the committed step of ABA catabolism. The contribution of ABA catabolism in root development remains unclear. We investigated the role of OsABA8ox2 in root growth and development and drought response. GUS staining results showed that OsABA8ox2 was expressed mainly in roots at seedling stage and was strongly expressed in the meristematic zone of the radicle. OsABA8ox2 expression in roots was markedly decreased after 0.5 h polyethylene glycol(PEG) treatment and increased after 0.5 h rehydration, implying that OsABA8ox2 is a drought-responsive gene.OsABA8ox2 knockout mediated by the CRISPR-Cas9 system increased drought-induced ABA and indole-3-acetic acid accumulation in roots, conferred increased ABA sensitivity, and promoted a more vertically oriented root system architecture(RSA) beneficial to drought tolerance.OsABA8ox2 overexpression suppressed root elongation and increased stomatal conductance and transpiration rate. Consequently, OsABA8ox2 knockout dramatically improved rice drought tolerance, whereas OsABA8ox2 overexpression seedlings were hypersensitive to drought stress,suggesting that OsABA8ox2 contributes to drought response in rice. Compared with wild type,functional leaves of OsABA8ox2 knockout seedlings showed higher ABA levels, whereas overexpression lines showed lower ABA levels, suggesting that OsABA8ox2, as an ABA catabolic gene, modulates ABA concentration through ABA catabolism. OsABA8ox2 and OsABA8ox3 were both localized in the endoplasmic reticulum. Together, these results indicate that OsABA8ox2 suppresses root elongation of rice seedlings, increases water transpiration, and contributes to drought response through ABA catabolism, and that OsABA8ox2 knockout dramatically improves rice drought tolerance. They highlight the key role of ABA catabolism mediated by OsABA8ox2 on root growth and development. OsABA8ox2, as a novel RSA gene, would be a potential genetic target for the improvement of rice drought tolerance.
基金Supported by Changsha Science and Technology Project(kq180103)Hunan Agricultural Science and Technology Innovation Fund Project(2017XC10)Hunan Agricultural Science and Technology Innovation Fund Project(2017JC12)~~
文摘The seedlings of 6 rice varieties were treated with Cd concentrations of 25,50 and 100μmol/L for 5 d.The results showed that the longest root length,seedling height,fresh weight per plant and dry weight per plant of 6 rice varieties were significantly inhibited.The inhibiting effects showed a trend as the following:the longest root length>fresh weight per plant>dry weight per plant>seedling height,and the inhibiting effect increased with the increase of Cd stress concentration.It is more economical and reasonable to use 50μmol/L Cd stress concentration to identify Cd tolerance of rice seedlings.And it is more scienti fic to evaluate the Cd tolerance of rice seedling comprehensively by using the 4 indexes of longest root length,fresh weight per plant,dry weight per plant and seedling height.
基金This work was funded by the National Natural Science Foundation of China(31871573)the Key Research and Development Program of Jiangsu Province,China(BE2017369)the Jiangsu Agriculture Science and Technology Innovation Fund,China(JASTIF)(CX(18)1002).
文摘The traditional soil-based rice seedling production methods for mechanical transplanting are resource-intensive,time consuming and laborious.The improvement and optimization of nutrient management in soil-less nursery raising methods like tandem long-mat seedlings(TLMS)are necessary for the resource-efficient cultivation of rice.In the present study,a controlled-release fertilizer(CRF)-polymer-coated compound fertilizer with 3 months release period(PCCF-3M)was applied as seedling fertilizer(SF),and five different dosages of SF(SF-0,SF-10,SF-20,SF-30,and SF-40)were compared with an organic substrate as the control(CK).Among all SF treatments,the best results were obtained with the application of 20 g/tray of SF(SF-20),as the seedling quality and machine transplanting quality were comparable to those of CK.In contrast,the lower dosages(SF-0 and SF-10)resulted in low nitrogen content and reduced shoot growth,while the higher dosages(SF-30 and SF-40)resulted in toxicity(increased malondialdehyde accumulation)and inhibited the root growth.Similarly,SF-20 increased panicle number(5.6-7.0%)and yield(4.3-5.3%)compared with CK,which might be related to the remaining SF entangled in the roots supporting the tiller growth of rice seedlings in the field.Moreover,SF-20 reduced the seedling block weight(53.1%)and cost of seedling production(23.5%)but increased the gross margin,indicating that it was easy to handle and economical.Taken together,our results indicate that SF-20 is a cost-effective way to promote the growth and transplanting efficiency of rice seedlings.To our knowledge,this study is the first to determine the optimum dosage of CRF for the soil-less production of rice seedlings.
基金supported by the National Key R&D Program of China (2017YFD0301503)the National Natural Science Foundation of China (31301267)the earmarked fund for China Agriculture Research System (CARS-01)
文摘This study was conducted to determine whether,and if so how,the grain yield and nitrogen(N) requirements of hybrid rice transplanted as single seedlings are affected by no-tillage(NT) practices.A fixed field experiment was done at the Experimental Farm of Hunan Agricultural University in Changsha,Hunan Province,China,from 2004 to 2014.Grain yield and yield attributes(panicle number per m2,spikelet number per panicle,spikelet filling percentage,grain weight,total biomass,and harvest index) were evaluated as well as the N-use characteristics(total N uptake,internal N-use efficiency,and N requirements) of hybrid rice transplanted as single seedlings comparing NT with conventional tillage(CT).A significant finding was that there were no significant differences in grain yield,yield attributes,and N-use characteristics between CT and NT.Averaged across the 11 years,grain yield and N requirements were 9.51 t ha^(-1) and 20.2 kg t^(-1) under CT and 9.33 t ha^(-1) and 20.0 kg t^(-1) under NT,respectively.There were significant yearly variations in grain yield,yield attributes,and N-use characteristics observed under both CT and NT.The yearly variation in grain yield was related to simultaneous changes in spikelet number per panicle,grain weight,total biomass,and harvest index.Also,it was found that grain yield was positively correlated with internal N-use efficiency but negatively correlated with N requirements.It is concluded that grain yield and N requirements in hybrid rice when transplanted as single seedlings are not affected adversely by NT.The results of this study suggest that(1) compatible relationships among yield attributes can be established in hybrid rice that is transplanted as single seedlings,and(2) higher grain yield and higher N-use efficiency can be concurrently achieved in hybrid rice transplanted as single seedlings.
基金supported by the National Natural Science Foundation of China (31560350 and 31760350)the Science and Technology Program of Jiangxi, China (20171ACF60018)
文摘Xanthine dehydrogenase(XDH) is a crucial enzyme involved in purine metabolism. To evaluate the effect of XDH deficiency on rice growth during dark treatment, wild type(WT) Nipponbare(Oryza sativa L.) and two independent transgenic lines with severe RNAi suppression(xdh3 and xdh4) were used in the present experiment. Under normal growth conditions, chlorophyll levels and biomass were indistinguishable between WT and the two RNAi transgenic lines, but XDH enzyme activity and ureide levels were suppressed in XDH RNAi transgenic lines. When XDH RNAi transgenic lines were subjected to dark treatment, chlorophyll content and biomass were significantly decreased, while O~–· production rate and malonaldehyde(MDA) were significantly increased compared to WT. The spraying test of exogenous allantoin raised chlorophyll content and biomass and reduced O~–· production rate and MDA in WT and both transgenic lines, and it also simultaneously reduced differences between RNAi and WT plants caused by XDH deficiency in growth potential and anti-oxidative capacity under dark treatment. These results suggested that fully functional purine metabolism plays an important role in reducing the sensitivity of rice seedlings to dark stress.