Regulation of ABA on Rice Root System Growth under Cadmium Stress

[Objective] The regulation of ABA on rice root system growth under Cd stress was studied.[Method] Taking rice Zhonghua No.11 as material,changes in rice root system growth were studied under the treatments of Cd,Cd ＋ ABA and Cd ＋ ABA inhibitor.[Result] Exogenous ABA could shorten the length of primary roots and adventitious roots of rice and could obviously inhibit the formation of lateral roots in primary roots and adventitious roots;ABA could obviously shorten the distance from root hair to root tip,but had little effect on the quantity of adventitious roots.[Conclusion] ABA takes part in the regulation in rice root system growth under Cd stress.

Regulation of Sucrose and Zinc on Root System Growth in Rice

[Objective] The aim was to study the relationship between urcrose, zinc and the root system growth in rice. [Method] Changes of root system growth, ROS generation and root system proton export ability were analyzed in rice （Oryza sativa L. cv Zhonghua No.11） treated with different concentrations of Zn （NO3）3 sucrose, com- bined sucrose and Zn （NO3）3 mannitol as well as mannitol plus Zn （NO3）2. [Result] The results showed that treatment with 1-3 mM Zn（NO3）2 resulted in significant increases in total root length /number and in accumulation of H202 and 02- but decreases in root system proton export ability. With the exception of shoot length, the length of primary, adventitious, and lateral roots, and the number of adventitious, and lateral roots on primary /adventitious roots were all influenced by different concentrations of sucrose. High concentrations of sucrose caused increases in H202 and O2-, starva- tion or high concentrations of sucrose reduced root system proton export ability after treating with or without Zn. However, at the same concentration of sucrose, different changes of these indicators were observed between Zn and non-Zn treatments. The regulation of root system growth induced by sucrose was marked different from that of mannitol at the same concentration of 5%, suggesting that these effects were caused by sugar signal but not by osmotic potential. [Conclusion] This study indicat- ed that both sucrose and Zn play important roles in the regulation of rice root system growth.

Effects of Superoxide Radical on Root System Growth and Auxin Distribution in Rice

[Objective] This study aimed to investigate the effect of superoxide radical on root system growth and auxin distribution in rice （Oryza sativa L. cv Zhonghua No.11）. [Method] With rice Zhonghua No.ll as the experimental material, the effects of DDC （SOD inhibitor） and Tiron （superoxide radical scavenger） on the root system growth, superoxide radical generation and root system auxin distribution in rice were analyzed. [Result] The growth and elongation of primary and adventitious roots were significantly promoted by DDC, while Tiron significantly inhibited the growth and elongation of shoots, primary roots and their lateral roots, and also suppressed the formation and growth of the adventitious roots as well as the elongation of their lateral roots. The superoxide radical was increased with the induction of DDC, while Tiron decreased the accumulation of superoxide radical. Increased accumulation of auxin in the vascular bundle and behind the elongation zone was observed in DDC- treated roots, while the treatment with Tiron resulted in a decrease of auxin in the same position. [Conclusion] This study indicated that the regulation of rice root sys- tem growth by superoxide radical was closely related with the accumulation and distribution of auxin.

Effect of Glucose on Zinc-induced Growth of Root System in Rice

[Objective] This study was aimed at exploring the effect of glucose signal on the zinc-induced growth of root system using rice as the material.[Method] The variation of root system growth,active oxygen production and proton secretion of root systems treated with various concentrations of glucose,glucose ＋ Zn（NO3）2,mannitol and Zn（NO3）2 ＋ mannitol were analyzed in rice（Oryza sativa L.cv Zhonghua no.11）.[Result] The results showed that the concentrations of glucose had affected the shoot height,primary root length,amount and length of lateral roots on primary roots,adventitious root length and length of lateral roots on adventitious roots in varying degrees,but not the amount of adventitious roots and lateral roots on adventitious roots under Zn＋ and Zn-condition.Glucose of high concentrations induced the production of active oxygen,while lacking of glucose would lead to the decrease of proton secretion of root systems.However,there were significant differences in these indexes between under Zn＋ and under Zn-condition treated with the same concentrations of glucose.The effects of glucose and mannitol with the same concentration on the growth of root systems were significantly different,indicating that the variation was resulting from sugar signal but not the osmotic potential.[Conclusion] The glucose had played important roles in the growth of rice root system both under normal condition and under Zn＋ condition.

Effects of Different Kinds of Exogenous Auxin on the Growth of Rice Roots under Cadmium Stress

[Objective] The aim was to study the effect of different kinds of exogenous auxin on the growth of rice roots under cadmium stress.[Method] Oryza sativa L.cv Zhonghua No.11 was used as experimental materials to detect the effect of different kinds of exogenous auxin on the growth of rice roots.[Result] The results showed that 0.1 mmol/L Cd treatment could not only increase primary,adventitious and lateral root length but also lateral root number,whereas the shoot growth was inhibited.When supplemented with different concentrations of NAA,IAA,IBA and 2,4-D,the growth of root system varied and similar change trend had been found.At the auxin concentration of 10^-9-10^-7 mol/L in particular 10^-8 mol/L,all four kinds of auxin promoted the elongation growth of primary and adventitious roots,but inhibition was observed when auxin was higher than 10^-7 mol/L.The decreased shoot growth caused by Cd could not be counteracted by supplementing with the four kinds of auxin.However,at the auxin concentration of 10^-9-10^-8 mol/L,NAA could improve rice growth under Cd stress condition.The formation and development of lateral roots on primary and adventitious roots was not only similar but also different after applying the same concentration of four auxins.[Conclusion] The addition of suitable amount of auxin under cadmium stress （such as 10^-9-10^-8 mol/L of NAA and so on） could ease the damage of cadmium on plants to a certain extent.

Enhancement of NH_4^+ Uptake by NO_3^- in Relation to Expression of Nitrate-Induced Genes in Rice (Oryza sativa) Roots

This study aimed to survey the expression of genes involved in rice N uptake and aasimilatory network and to understand the potential molecular mechanisms responsible for the NO3^-enhanced NH4^＋ uptake. By using quantitative real-time polymerase chain reaction （PCR）, the genes related to N nutrition, including ammonium transporters （AMTs） and ammonium assimilatory enzymes （GS and GOGAT）, were transcriptionally analyzed in rice plants grown in the absence and presence of NO4^- in the NH4^＋-containing medium. The results showed that NH4^＋ uptake by rice was enhanced by the NO3^- supply to the medium. At the same time and in parallel, the amount of transcripts of seven genes （OsAMT1;1, OsAMT1;2, OsAMT4;1, OsGLNP, OsGLU1, OsGLT1, and OsGLTP） was increased in rice roots, but the expression of two genes （OsGLN1;1 and OsGLN1;P） was decreased and that of OsAMT1;3 remained without change. Up- or downregulation of these genes involved in NH4^＋ uptake and assimilation correlated with the increase in NH4^＋ uptake in the presence of NO3^- in rice roots.

MT 10 Mutant of Rice with Altered Lateral Root Initiation

Mutants with increased resistance to toxic anxin concentrations were first isolated in rice.The present report describes their isolation,genetics and physiological characterization.

Effect of Exogenous Ammonium on GlutamineSynthetase, Glutamate Synthase, and Glutamate Dehydrogenase in the Root of Rice Seedling

Root biomass of rice seedlings was increased at lower concentration of exogenous NH 4 + , but it was decreased at higher concentration of exogenous NH 4 + . The level of free NH 4 + in the roots was accumulated gradually with the increase of NH 4 + concentration in the nutrient solution. The content of the soluble proteins was essentially constant at higher NH 4 + . The activities of glutamine synthetase (GS), NADH-dependent glutamate synthase (NADH-GOGAT), and NADH-dependent glutamate dehydrogenase (NADH-GDH) were risen with exogenous NH 4 + concentration at the lower NH 4 + concentration range. But the activities of GS and NADH-GOGAT were declined, and the level of NADH-GDH activity was kept constant under higher NH 4 + concentration. The GS/GDH ratio suggested that NH 4 + was assimilated by GS-GOGAT cycle under lower NH 4 + concentration, but NADH-GDH was more important for NH 4 + assimilation and detoxifying NH 4 + to the tissue cells at the higher NH 4 + level. According to the growth and the activity changes of these ammonium-assimilating enzymes of rice seedling roots, 10. 0 μg/mL NH 4 + -N in nutrient solution was more suitable to the rice growth.

Suberin Biopolymer in Rice Root Exodermis Reinforces Preformed Barrier Against Meloidogyne graminicola Infection

Exploration of novel genetic resources against root-knot nematode(RKN)is necessary to strengthen the resistance breeding program in cultivated rice,and investigations on the role of genotype-specific root anatomy in conferring a structural barrier against nematode invasion are largely underexplored.Here,we reported a highly-resistant rice germplasm Phule Radha that conferred remarkably lower RKN parasitic fitness in terms of reduced penetration and delayed development and reproduction when compared with susceptible cultivar PB1121.Using histological and biochemical analyses,we demonstrated that an enhanced suberin deposition in the exodermal root tip tissue of Phule Radha compared to PB1121 can effectively form a penetrative barrier against RKN infection,and this preformed barrier in the control tissue did not necessarily alter to a greater extent when challenged with RKN stress.Using qRT-PCR analysis,we showed that a number of suberin biosynthesis genes were greatly expressed in the exodermis of Phule Radha compared to PB1121.In sum,the present study established the role of rice exodermal barrier system in defense against an important soil-borne pathogen.

OsABA8ox2, an ABA catabolic gene, suppresses root elongation of rice seedlings and contributes to drought response

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.

Effects of CO_2 laser on chromosomal aberration in the root tip cells of rice

Seeds of japonica rice cv.Zhenuo 2 with twodifferent physiological states(dry seeds withwater content 13% and wet seeds soaked in thewater for 36 h)were irradiated by COlaser infour different power-densities and durations re-spectively.The treatment irradiated with 200GY ofCo γ-rays was considered as control.The flesh root tips were cut and fixed inCarnoy’s fluid for cytological examination.

Studies on the Mechanism of Single Basal Application of Controlled-Release Fertilizers for Increasing Yield of Rice (Oryza sativa L.)

This paper was to explore the mechanism of single basal application of controlled-release fertilizers for increasing yield of rice （Oryza sativa L.）. Pot trials and cylinder trials were carried out from 2002 to 2005 to study the influences of single basal application of 3 controlled-release fertilizers on the changes of soil available N, root development, senescence and lodging resistance at late growth stages. Results showed that at 30 days after fertilization, single basal application of controlled-release fertilizers coated with vegetal-substance （CRF1） and polymer materials （CRF3） increased soil available N to 12.0 and 147.9%, respectively, in comparison to split fertilization of rice-specific fertilizer （RSF1）. Treatments of the two CRFs obviously benefited the development of root system, resulting in greater rice root weights with extensive distribution and higher root activity. In addition, the two CRF treatments, in comparison to RSF1, enhanced chlorophyll consents of the flag leaves to 9.5 and 15.5%, and soluble protein up to 89.7 and 108.0% respectively. Application of the two CRFs also made the base of rice stems strong and large, declined the proportion of shoot and root, increased root depth index. Though relatively low K rate, single basal application of the CRF3 coated with NH4MgPO4 could also promote the development of root system, enhance root activity and some physiological functions of flag leaves. Based on these results, it was concluded that major mechanisms for increasing rice yield by single basal application of the CRFs should be attributed to grater soil available N supply, superior development of root systems, better nutrient absorption capacity, slower senescence and enhancement of lodging resistance at late stages.

Hydrogen Peroxide-Mediated Growth of the Root System Occurs via Auxin Signaling Modification and Variations in the Expression of Cell-Cycle Genes in Rice Seedlings Exposed to Cadmium Stress

The link between root growth, H2O2, auxin signaling, and the ceil cycle in cadmium （Cd）-stressed rice （Oryza sativa L. cv. Zhonghua No. 11） was analyzed in this study. Exposure to Cd induced a significant accumulation of Cd, but caused a decrease in zinc （Zn） content which resulted from the decreased expression of OsHMA9 and OsZIP. Analysis using a Cd-specific probe showed that Cd was mainly localized in the meristematic zone and vascular tissues. Formation and elongation of the root system were significantly promoted by 3-amino-l,2,4-triazole （AT）, but were markedly inhibited by N,N＇. dimethylthiourea （DMTU） under Cd stress. The effect of H2O2 on Cd-stressed root growth was further confirmed by examining a gain-of-function rice mutant （carrying catalasel and glutathione-S-transferase） in the presence or absence of diphenylene iodonium. DR5-GUS staining revealed close associations between H2O2 and the concentration and distribution of auxin. H2O2 affected the expression of key genes, including OsYUCCA, OsPIN, OsARF, and OslAA, in the auxin signaling pathway in Cd-treated plants. These results suggest that H2O2 functions upstream of the auxin signaling pathway. Furthermore, H2O2 modified the expression of cell-cycle genes in Cd-treated roots. The effects of H2O2 on root system growth are therefore linked to auxin signal modification and to variations in the expression of cell-cycle genes in Cd-stressed rice. A working model for the effects of H2O2 on Cd-stressed root system growth is thus proposed and discussed in this paper.

水田搅浆方式对水稻根系生长及产量的影响

为揭示水田不同搅浆方式对寒区水稻根系形态结构和生理活性的影响及其与产量形成之间的关系,本研究以龙粳31为试验材料,设置旱平免搅浆(HP)、水平地免搅浆(SP)、常规搅浆(CK)3种搅浆方式进行对比试验,对各生育期水稻根系形态结构指标、根系生理活性指标、干物质量及产量进行测定。结果表明:水稻根系形态指标在抽穗扬花期趋于稳定,与CK相比,HP处理下的总根长、根表面积、根体积和平均直径分别显著增加14.1%、8.79%、7.16%和4.06%,SP处理下仅总根长显著增加6.43%。水稻根系生理活性指标在抽穗扬花期达到最大值,与CK相比,HP和SP分别使根系氧化活力显著增加16.1%和5.51%,根系伤流强度显著增加10.2%和5.74%。同时,与CK相比,HP和SP的水稻产量分别显著提高7.65%和4.03%。综上所述,HP能够明显改善根系形态,促进根系生长,提高根系生理活性,进而促进水稻植株地上部生长和产量的增加。

盐碱胁迫水稻根系研究

我国盐碱地面积约为1×108 hm2,其中可利用的盐碱地约0.37×108 hm2,盐碱地是重要的耕地后备资源,开发利用潜力巨大。开发种稻是盐碱地改良和利用的有效措施,水稻根系研究对挖掘盐碱水田增产潜力具有重要意义。本文概述了国内外盐碱胁迫水稻根系的研究现状,重点从盐碱胁迫对水稻根系表型、抗逆生理及产量形成的影响等方面的研究进展进行了综述,并对该研究领域未来发展进行了展望。以期多角度全面解析盐碱胁迫水稻根系逆境形态和生理机理,明确土壤-根系-产量的互作机制,基于优良种质资源结合育种技术构建理想根系构型,为挖掘盐碱地水稻增产潜力提供参考。

宁夏盐碱地水稻根系形态和生理指标与产量的相关分析及综合评价

【目的】比较分析宁夏盐碱地不同水稻品种(系)根系形态和生理指标与产量的关系,筛选适宜宁夏盐碱地种植的高产水稻品种(系),为宁夏盐碱地高产水稻品种的选育和种植提供参考。【方法】以4个宁夏常规水稻种植品种(宁粳52号、宁粳57号、96D10、HJW14)和1个海稻86衍生系(陈2)为试验材料,在宁夏盐碱地进行大田种植试验,在生育期关键节点(苗期、分蘖期、抽穗期和灌浆期)测定根系形态指标(根直径、根长、根表面积、根体积、根鲜重和根干重)、生理指标[超氧化物歧化酶(SOD)活性、过氧化物酶(POD)活性、根系活力、根系总吸收面积和根系活跃吸收面积]和产量及构成因素指标(穗数、穗粒数、千粒重、结实率、产量),并利用相关分析、主成分分析和隶属函数法对不同品种(系)水稻进行综合评价。【结果】不同水稻品种(系)的根直径随着生育期的推进呈逐渐增加趋势,根长、根表面积、根体积在苗期到抽穗期呈逐渐增加趋势,在抽穗期到灌浆期呈下降趋势。宁粳52号、宁粳57号和陈2的根系形态整体表现优于96D10和HJW14。陈2和宁粳57号的根系活力优于宁粳52号、96D10和HJW14。宁粳52号、宁粳57号和陈2的根系总吸收面积和根系活跃吸收面积整体上高于96D10和HJW14。宁粳52号、宁粳57号和陈2在不同生育期的SOD和POD活性均高于96D10和HJW14。在产量表现方面,宁粳52号的产量最高,达7420.97 kg/ha,HJW14的产量最低,为4970.94 kg/ha。相关分析结果表明,产量与根系总吸收面积呈显著正相关(P<0.05),与SOD和POD活性呈极显著正相关(P<0.01);主成分分析结果确定根长、根表面积、根鲜重、根干重、根系活力、根系活跃吸收面积、SOD活性和千粒重为耐盐碱关键指标。利用隶属函数结合权重分析法得到不同水稻品种(系)耐盐碱的综合评价值(D)排序为宁粳57号>宁粳52号>陈2>96D10>HJW14。【结论】综合D值与实际产量考虑,宁粳52号在盐碱地表现相对较好,适宜作为宁夏盐碱地种植与示范的高产水稻品种。

种植方式与施氮量对杂交籼稻养分吸收特性及根系活力的影响

为探明不同种植方式与施氮量对杂交籼稻养分吸收特性、产量及根系活力的影响,以杂交籼稻F优498为试验材料,采用二因素裂区设计,主区为3种种植方式(毯苗机插、湿润精量穴直播和人工移栽),副区为4个施氮量(0 kg hm^(-2)、90 kg hm^(-2)、135 kg hm^(–2)和180 kg hm^(–2)),探究F优498在不同处理下对养分积累、根系活力、产量及其构成因子的影响。结果表明,水稻抽穗期及成熟期的氮积累量均为人工移栽>机插>直播,拔节期磷积累总量和抽穗期钾积累总量均为人工移栽最大,拔节前直播稻的氮、磷和钾积累速率最高,分别比机插和人工移栽高40.68%~63.64%和19.42%~71.43%,不同种植方式下均在拔节至抽穗期养分积累速率达到最大;人工移栽和机插方式下水稻产量差异不显著,直播与人工移栽相比,减产8.09%~15.00%,人工移栽的水稻千粒重、穗粒数和结实率均高于机插和直播,但有效穗数显著降低,分别比机插和直播低15.99%~41.77%和23.19%~29.60%,施氮后产量的显著提高是由于提高了单位面积有效穗数和每穗粒数;各种植方式的地上部和根系干物重分别在成熟期和抽穗期达到最大,就不同施氮量而言,施氮处理的群体根系干物重显著高于不施氮处理;水稻抽穗后单茎和群体伤流强度降低,机插的单茎及群体根系活力显著高于人工移栽和直播。机插稻施氮量在中低氮水平(90~135 kg hm^(-2))较适宜,直播稻和人工移栽稻施氮量在中高氮水平(135~180 kg hm^(-2))较适宜。

水稻颖花根活量与籽粒灌浆结实的关系

1986—1990年,在群体水培、大田及盆栽条件下,对不同类型水稻品种、不同氮素处理的根量、活力、籽粒灌浆结实、物质积累与分配等进行了研究。结果表明:(1)水稻品种间根量差异较大,主要由上层根量不同所致;(2)结实期平均根系活力随品种伸长节间数的增加呈下降趋势,与根量呈负相关;(3)不同生育期氮素处理对根量的影响以前期最大、中期次之、后期最小;(4)生育前期缺氮下层根系活力下降幅度较大,中期缺氮上层根系活力下降幅度较大,后期则因稻体含氮水平而异;(5)结实期颖花根活量与籽粒的灌浆强度、结实率、粒重均呈极显著正相关,提高颖花根活量能显著地提高净同化率,并促进同化产物向籽粒和根系输送,较少地滞留在叶内。认为增加颖花根活量是提高水稻结实率和粒重的有效途径。并对水稻高产栽培途径进行了探讨。

水稻根系的空间分布及其与产量的关系

选择9个水稻品种,在水稻生长根系最旺盛的抽穗期进行取样,研究高产水稻群体的根系空间分布特征.结果表明:不同水稻品种的根系体积和质量的总量存在差异.各品种水稻根系的体积和质量均随土层深度增加而下降,但主要分布在土壤耕作层(0～20cm),且表层(0～10cm)占80%以上.其垂直分布可用指数模型、乘幂模型、对数函数、多项式函数表示,相关系数都在0.9以上.上层根(0～10cm)质量与产量之间没有显著的相关关系,而下层根质量(10cm以下)与产量之间呈显著正相关关系,相关系数达0 7258.研究认为,从整株根系和高产的角度来看,适当减少表层根系,培育和增加深层根系的比例有利于促进水稻产量的提高.