Physiological Responses of Brazil Banana Seedlings to Drought Stress Simulated by PEG-6000

[Objective] The aim was to explore physiological responses of Brazil banana seedlings to drought stress simulated by PEG-6000.[Method] Brazil banana （Musa AAA Cavendish subgroup cv.Brazil） was taken as test materials to explore changes of physiological indices of banana seedlings under drought stresses simulated by PEG-6000,including three stress levels （5％,10％ and 15％） and time periods （24,48 and 72 h）.[Result] Relative water content and chlorophyll content both declined under different stress levels and in different times.The content of proline （Pro） in seedling leaves from high to low was PEG15％,PEG10％ and PEG5％; the content of treatment of 5％ stress in 24 h was of insignificant differences with that of the control and the contents in rest treatments were all remarkably higher compared with the control.POD activities of seedling leaves from high to low were as follows：PEG15％＞PEG10％＞PEG5％,and POD activity was of significant differences among treatments; POD activity achieved the peak in treatment group with 5％ of stress,and POD activities of different groups were all higher compared with the control.The activity of root system in treatment groups with PEG at different concentrations was as follows：PEG10％＞PEG15％＞PEG5％ and the activity increased remarkably in the group with PEG at 5％ within 24,48 and 72 h,though the activity dropped significantly within 72 h and slowly in 24 and 48 h.[Conclusion] It can be concluded that relative water content,chlorophyll content,Pro content and activity and root activity can be references of banana resistance to drought.

Effects of Remaining Leaf Combining with IBA on Rooting,Physiological and Biochemical Indicators of Leaves from Bougainvillea spectabilis Cuttings

[Objective] The research aimed to discuss the effects on rooting,physiological and biochemical indicators of Bougainvillea spectabilis cuttings by remaining leaf combining with soaking cuttings in IBA.[Method] Effects of remaining leaf combining with IBA on rooting,physiological and biochemical indicators of B.spectabilis cuttings were studied under the regulation and control of intelligent seed propagation system,and then set four treatments：remaining leaf combining with soaking in clean water,remaining leaf combining with soaking in IBA,defoliation combining soaking in clean water,and defoliation combining with soaking in IBA.[Result] The soluble sugar content was high,but indoleacetic acid oxidase activity was lower in the initial stage of adventitious root differentiation in treatment of remaining leaf.While the rooting number,root length,the root mass growth and survival rate of cutting were obviously higher than that in treatment of defoliation.Compared to the treatment soaking in clean water,the treatment soaking in 500×10^-6 IBA increased the soluble sugar content in leaves of cuttings and enhanced rooting of cuttings.[Conclusion] The survival rate and rooting of cuttings improved obviously in the treatment of remaining leaf combining with soaking in 500×10^-6 IBA before cutting under the regulation and control of intelligent seed propagation system.

Effects of Exogenous Vc on Seed Germination and Physiological Properties of Oil Sunflower(Helianthus annuus) under Salt Stress

[Objective] This study aimed to provide the theoretical and technical basis for alleviating salt damages in production practice of oil sunflower （Helianthus annuus）. [Method] Seeds of oil sunflower were used as experimental materials and treated with 120 mmol/L NaCI solution and 0-200 mg/L Vc solution during the germina- tion process, to investigate the effects of exogenous Vc on seed germination and physiological properties of oil sunflower under salt stress. [Result] Under salt stress, with the increase of Vc concentration, germination potential and germination rate of oil sunflower seeds, superoxide dismutase （SOD） and peroxidase （POD） activities and proline （Pro） content of oil sunflower seedlings increased first and then declined, which reached the maixmum in 80 mg/L Vc treatment, 120 mg/L Vc treatment and 80 mg/L Vc treatment, respectively; malondialdehyde （MDA） content of oil sunflower seedlings declined first and then increased, which reached the minimum in 160 mg/L Vc treatment. [Conclusion] To varying degrees, Vc could improve germination potential and germination rate of oil sunflower seeds and promote seedling growth under salt stress, thus alleviating the damages of salt stress to seed germination and seedling growth of oil sunflower.

Selenium Regulates Antioxidant Capacities and Diterpenoid Biosynthesis in the Medicinal Plant Isodon rubescens

Dōng líng căo,the dried aboveground parts of Isodon rubescens(Hemls.)Hara.,is commonly consumed as a med-icinal decoction or tea beverage.Natural beverages can be an important source of human dietary selenium(Se).However,how I.rubescens plants respond to exogenous Se remains unknown.In this study,a pot cultivation experiment was employed to investigate the phenotypic and physiological responses of I.rubescens plants exposed to Se.Fifteen days after applying different concentrations of sodium selenate to the soil,the Se enrichment capa-city,growth indices,antioxidant capacities,and the content offlavonoids and diterpenoids were measured in the plants.Further,the oridonin content was quantified using the high-performance liquid chromatography method,and the expression levels of key diterpenoid synthesis genes were analyzed by quantitative real-time PCR(qRT-PCR).I.rubescens plants efficiently accumulated Se,with the Se content increasing proportionally to the applied dose,reaching levels of nearly 200 mg·kg^(-1) dry leaves as Se concentration increased.None of the three Se treat-ments significantly altered the phenotypic indices,except a longer root length occurred in the 3μM·kg^(-1) Se group.Among three Se doses,6μM·kg^(-1) Se gave the highest accumulation offlavonoids,diterpenoids,and oridonin,with the increase of 2.0-,1.8-,and 1.9-fold in aboveground parts,respectively.Selenium application boosted the activities of antioxidant enzymes and antioxidant capacities according to 2,2-Diphenyl-1-picrylhydrazyl(DPPH),ferric reducing/antioxidant power,and tea brewing color experiments.Four key synthase genes were upregulated significantly by 6μM·kg^(-1) Se treatment,notably 1-deoxy-D-xylulose 5-phosphate reductoisomerase(IrDXR),with a 5-fold increase,and kaurene synthase-like 4(IrKSL4),with a 6-fold increase.Thus,Se application in I.rubescens cultivation may be a potential biofortification method to supplement Se while increasingflavonoid and diterpenoid contents.

Effects of Silicon Formulations on Cold Tolerance of Rice Seedlings

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.

Study on Effect of Drought Stress with PEG-6000 on Physiological and Biochemical Indicators in Kadsura coccinea

[Objective] The aim was to research drought resistance and adaptation mechanisms of Kaclsura coccinea under different drought stresses. [Method] The seedlings of Kadsura coccinea growing one year were taken as materials in order to investigate and analyze leaf SPAD value, relative water content （RWC）, malonaldehyde （MAD）, cell membrane permeability （RP）, proline （PRO） and superoxide dismutase activity （SOD）. [Result] As drought stress improved, leaf SPAD value and RWC were both diminishing and RWC fell remarkably; MAD, Pro, RP and SOD activity were increasing; MAD and RP grew significantly. [Conclusion] Kadsura coccinea is much sensitive to drought stress and will be affected if water loss is too much high.

Physiological evaluation of nitrogen use efficiency of different apple cultivars under various nitrogen and water supply conditions

Nitrogen(N) deficiency is a common problem for apple(Malus×domestica) production in arid regions of China.However,N utilization efficiency(NUE) of different apple cultivars grown under low N conditions in arid regions has not been evaluated.In this study,NUE was assessed for one-year-old seedlings of six apple cultivars,Golden Delicious,Qinguan,Jonagold,Honeycrisp,Fuji and Pink Lady,grafted onto Malus hupehensis Rehd.rootstocks.Four treatments were used,including control water with control N(CWCN),limited water with control N(LWCN),control water with low N(CWLN) and limited water with low N(LWLN).Our results showed that growth indices such as biomass,plant height and stem diameter,and photosynthetic rate of all cultivars decreased in the order CWCN>CWLN>LWCN>LWLN.When subjected to LWLN treatment,Qinguan showed better growth and photosynthetic characters than other tested cultivars.Additionally,Qinguan and Pink Lady had higher NUE,while Honeycrisp and Jonagold had lower NUE,based on the determination of biomass,photosynthetic parameters,chlorophyll content,the maximal photochemical efficiency of PSII(Fv/Fm),15 N and N contents.

Effects of 1-aminobenzotriazole on the growth and physiological characteristics of Tamarix chinensis cuttings under salt stress

vegetation restoration is a main ecological remediation technology for greening saline and alkaline soils.The objectives of this study were to determine the effect of1-aminobenzotriazole(ABT-1) on the growth and physiology of Tamarix chinensis under salt stress and to determine a suitable ABT-1 concentration and soil salinity(Sc) for propagating T.chihehsis-cuttings.Cuttings were soaked in water and ABT-1 solutions at three concentrations(50,100,and 200 mg L^(-1)) and propagated in pots containing four soil salinity levels,mild(0.3%),moderate(0.6%),and severe(0.9% and 1.2%),and compared with a control.The cuttings were measured to determine growth indices and physiological and biochemical indices(e.g.,chlorophyll content,superoxide dismutase activity,peroxidase activity,and malondialdehyde content).ABT-1 was effective in improving survival,growth,and physiological processes of cuttings under salt stress.However,there was a threshold effect when using ABT-1 to facilitate propagation under salt stress.ABT-1 effects were insignificant when applied at low concentrations(<100 mg L^(-1)).At a high concentration(> 100 mg L^(-1)),ABT-1 limited growth and physiological activities.Under a salt stress level(Sc ≤0.9%),ABT applied at a 100 mg L^(-1)concentration increased chlorophyll content and superoxide dismutase and peroxidase activities in the leaves and reduced malondialdehyde accumulation and membrane lipid peroxidation effects.As a result,ABT-1 enhanced the resistance of T.chinensis to salt stress.However,under high salt stress(>0.9%) and ABT-1 concentration(> 100 mg L^(-1)),the physiological regulatory ability of T.chinensis seedlings weakened.T.chinensis grew well at a salt stress ≤0.9% and ABT ≤100 mg L^(-1) and exhibited relatively high physiological regulatory ability and high salt adaptability.

Physiological Indices and Selection of Methods on Rapid Identification for Sweet Potato Drought Resistance

The relationships between the changes of relative water content （RWC）, malondialdehyde （MDA） contents, superoxide dismutase （SOD） activity and free proline contents in sweet potato leaves, and drought resistant ability under different concentration of polyethylene glycol （PEG） treatment applied at rhizosphere of sweet potato seedlings were studied. A highly positive correlation between RWC and drought resistance （r =0.783, P〈0.01）, a highly negative correlation between MDA contents and drought resistance （r = -0.848, P〈0.01）, a highly positive correlation between SOD activity and drought resistance （r = 0.777, P〈0.01） was observed. Free proline contents in leaves was not related obviously to the sweet potato drought resistance under 25% PEG treatment. The stronger the drought resistance of variety, the less decrease of RWC and increase of MDA contents, the more increase of SOD activity. By determining these physiological indices in sweet potato leaves under 25% PEG treatment, rapid identification of drought resistant ability of different varieties can be obtained in the lab.

Changes in Several Physiological and Biochemical Indices of Maize Seedling Roots Caused by Drought Stress

The changes in several physiological and biochemical indices of seedling roots of new maize variety Qingnong 8 were studied under the simulated drought condition with 18% PEG-6000 and water shortage. The results showed that under drought conditions, the contents of soluble protein and malonialdehy （MDA） and the activities of superoxide dismutase （SOD） and peroxidase （POD） in roots of maize seedlings significantly increased, and the increasing amplitude reduced after water shortage for 96 h. The re-watering treatment results after 48 h water shortage showed that the SOD and POD activities and the MDA content could recover to normal level, and the soluble protein content was lower than normal content. This study showed that the maize seedlings of Qingnong 8 suffered drought injury could grow normally after re-watering treatment.

Impact of Asarum Essential Oils on Physiological and Biochemical Indicators of Two Agricultural Pests

[Objective]The paper was to study the effects of asarum essential oils on physiological and biochemical indices of two agricultural pests. [Method]Asarum essential oils were extracted by different methods,and their effects on physiological and biochemical indices related to the structure of body wall（ chitin and phenoloxidase）,the physiological and biochemical indices acting on the nervous system（ Acetylcholinesterase）,and the physiological and biochemical indices acting on the digestive system（ protease,amylase and lipase） of Ostrinia furnacalis and Mythimna seperata were studied. [Result]Asarum essential oils had no effect no chitin content of body wall under the experimental concentration,and had no inhibitory effect but activated effect on polyphenol oxidase activity. Asarum essential oils could act on the nervous system of insect,and had strong inhibitory effect against acetylcholinesterase activity of O. furnacalis larvae,with inhibition rates of 24. 86%- 38. 79%. Asarum essential oils showed a significant activated effect on pepsin activity in midgut,but the activated amplitude became smaller with the prolongation of treatment time. Asarum essential oils showed a significant inhibitory effect on activities of amylase and lipase,indicating that it could play an insecticidal effect by inhibiting activity of amylase and lipase,and it could act on digestive system of insect. [Conclusion]The study laid the foundation for further development of asarum as botanical pesticide.

Determination of Physiological and Biochemical Indicators of Brown-Egg Dwarf Layers at Different Ages

[ Objective] To observe biological characteristics of brown-egg dwarf layers. [ Method ] Physiological and biochemical indicators of brown-egg dwarf layers were determined at the age of 20, 40 and 60 weeks, respectively. Fifty-four chickens were detected, nine roosters and nine hens at each age. [Result] As analyzed by ttest and multiple comparisons, during 20 -60 weeks old, the RBC, HGB, MPV, PDW, LYMPH%, TP and CHO showed an increasing trend. However, during this period, the HCT, MCV, RDW, WBC and LYMPH first decreased and then de- clined, while the MCH, MCHC, PLT, PCT, MID, MID%, GRAN, GRAN%, AST, ALB, TG, ALT and GLU changed contrarily. The chickens at different ages had significantly different physiological and biochemical indicators （P 〈 0.05）. The RBC, HCT, HGB, WBC, LYMPH and AST were significantly different between the roosters and hens during 20 -60 weeks old. [ Conclusion] In the brown-egg dwarf layers, the physiological and bi- ochemical indicators vary with aging, and their difference levels also change with aging.

Effects of Chinese Herbal Compound on the Blood Physiological Indices and Cytokines of Myelosuppressive Mice

[ Objective ] The research aimed to study the effects of Chinese herbal compound on the blcod physiological indices and cytokines of myelosuppressive mice. [ Metho] Myelasuppressive mice model was established by intraperitoneal injection of 80 mg/kg cyclophosphamide. Chinese herbal compound was composed of Houttuynia cordata, Taraxacum mongolicum, Citrus reticulata peel, Atractylodes chinensis, Paeonia sterniana, Atractylodes macrocephala and Angelica sinensis. The effects of Chinese herbal compound and Astragalus polysaccharide at different doses on the blood physiological indices and hematopoietic growth factors of myelosuppressive mice were discussed. [ Result] Myelosuppressive mice medel was successfully established. The total white blood cell count, total nentrephile granulocyte count, total lymphocyte count, total platelet count and the contents of serum interleukin-6 and erythropoietin in myelosuppressive mice were significantly decreased. The total erythrocyte count, the contents of hemoglobin and imerleukin-3 were decreased, without significant difference. The blood physiological indices and the contents of interleukin-3 and erythropoietin in myelosuppressive mice could be improved by intragastric administration of Astragalus polysaccharide and Chinese herbal compound at different doses for 3 days or 7 days. The effect of 20 g/kg Chinese herbal compound was the best after administration for 3 days, and the effect of 10 g/kg Chinese herbal compound was the best after administration for 7 days. The total white blcod cell count, total neutrophile granulocyte count, percentage of neutrephile granulocyte, total lymphocyte count, total count of middle cells, percentage of middle cells, total platelet count, contents of interleukin-3 and erythropoietin in myelosuppressive mice could be extremely significantly improved by intragastric administration of 10 g/kg Chinese herbal compound for 7 days（ P 〈 0. 01 ） , and the reduction of red blood cell count, hematecfit, the contents of hemoglobin and interleukin-6 induced by cyclophesphamide could be inhibited （P 〈 0.01 ）. [ Conclusion ] Chinese herbal compound could improve the hematopoietic function of myclosuppressivc mice induced by cyclophosphamide and its effect was better than Astragalus polysaccharide. 20 g/kg Chinese herbal compound reacted fast and the reaction of 10 g/kg Chinese herbal compound was slow ,but its efficacy was lasting.

Research on Physiological Characteristics of Tall Fescue under Nitrogen Stress

[Objective] This study aimed to investigate the physiological characteristics of tall fescue under nitrogen stress. [Method] A series of physiological changes in protein content, chlorophyll content, enzyme activities and amino acids contents in tall fescue under nitrogen stress were analyzed. [Result] Under nitrogen stress, the leaf chlorophyll content in tall fescue was reduced, and superoxide dismutase（SOD）,peroxidase（POD）, glutamine synthetase（GS） activities were increased. Among the 18 kinds of amino acids analyzed, the contents of asparagine, serine, glycine, glutamine, glutamic acid, aspartic acid, threonine, alanine, arginine, methionine, valine,isoleucine and leucine were significantly reduced in tall fescue under nitrogen stress.[Conclusion] This study will provide certain reference for rational application of nitrogen and exploration of plant ecological potential in the future.

Effect of foot reflexology on pain and physiological indicators in postoperative patients:A systematic review and meta-analysis

Aim:To determine the effect of foot reflexology intervention on pain and physiological indicators in postoperative patients.Data resources:The Cochrane library,PubMed,EMBASE,MEDLINE,SCOPUS,CINAHL,China National Knowledge Infrastructure(CNKI),VIP,and Wan Fang Data were searched from inception until January2020.Review methods:Studies were screened according to the PICOS principle.The methodological quality was assessed with Cochrane Risk of Bias Tool.Meta-analysis was performed using RevMan 5.3 software.Results:5 randomized clinical trials involving 318 participants were included in the meta-analysis.There were significant differences in pain and heart rate in postoperative patients between the two groups.Conclusion:The foot reflexology intervention decrease the postoperative pain and heart rate for the postoperative patients.It can be considered to be an effective non-pharmaceutical therapy to reduce the postoperative pain and heart rate.The evidence is not enough to prove the effectiveness of reducing postoperative blood pressure,respiratory rate,pulse rate and oxygen saturation using the foot reflexology.

Determination of Physiological and Biochemical Indices of Hailan Chickens at 20 Weeks of Age

[Objective]This study aimed to determine physiological and biochemical indices of Hailan chickens at 20 weeks of age.[Method]T,P,BT,CT,ESR,systolic pressure,diastolic pressure,RBC,HCT,MCV,RDW,HGB,MCH,MCHC,PLT,MPV,WBC,N,E,B,L,M,TP,Alb,AST,ALT,Glu and TG and CHO of 20 weeks-old male and female Hailan chickens were determined with various methods.[Result]According to the determined blood physiological and biochemical indices,RBC,HGB,Glu and ALB in male chickens were higher compared with female chickens,exhibiting extremely significant differences（P〈0.01）;B,M and TP in male chickens were significantly higher compared with female chickens（P〈0.05）;other physiological and biochemical indices exhibited no significant differences between males and females（P〉0.05）.[Conclusion]Physiological and biochemical indices of 20 weeks-old Hailan chickens varied between males and females,which were generally higher in male chickens than in female chickens.

Brassinosteroids Mediate Endogenous Phytohormone Metabolism to Alleviate High Temperature Injury at Panicle Initiation Stage in Rice

High temperatures cause physiological and biochemical changes and significantly affect young panicle development of rice(Oryza sativa L.).Brassinosteroids play important roles in enhancing crop stress resistance.In this study,we subjected rice cultivars Huanghuazhan(heat-resistant)and IR36(heat-sensitive)to high temperature(HT,40 oC)or normal temperature(NT,33 oC)for 7 d at the panicle initiation stage,in conjunction with application of 24-epibrassinolide[EBR,a synthetic brassinolide(BR)]or brassinazole(BRZ,a BR biosynthesis inhibitor)at the beginning of the treatments.HT exacerbated spikelet degeneration and inhibited young panicle growth,which were partially prevented by EBR application,while BRZ application aggravated the reduction in spikelet number.HT decreased the contents of BR,active cytokinins(aCTK),active gibberellins(aGA)and indole-3-acetic acid(IAA),but increased the content of abscisic acid(ABA)in young panicles.The activities of key enzymes involved in sucrose hydrolysis,glycolysis and the tricarboxylic acid cycle in young panicles were decreased with the change of endogenous hormone levels under HT.In addition,the contents of H2O2 and malondialdehyde(MDA)were increased and the activities of antioxidant enzymes were decreased in young panicles.Exogenous application of EBR induced the expression of phytohormone biosynthesis-related genes and down-regulated the expression of phytohormone catabolism-related genes to increase the contents of endogenous BR,aCTK,aGA and ABA,thus promoting the decomposition and utilization of sucrose in young panicles,enhancing the activities of superoxide dismutase,catalase and peroxidase,and reducing the accumulation of H2O2 and MDA in young panicles,whereas application of BRZ had the opposite physiological effects.These results showed that brassinosteroids mediate endogenous phytohormone metabolism to alleviate HT injury at the panicle initiation stage in rice.

Evaluation of Drought Resistance of Olive Varieties from Different Provenances

In order to study olive’s drought resistance in Yunnan province, different varieties of olive trees from Albania, Italy, Spain and Greece were cultured, and leaves from these trees in drought season and rainy season were col ected and determined by physiological indices, such as proline content, relative electric con-ductivity, binding water/free water, relative water content and malon-dialdehyde in leaves. The evaluation of drought resistance with subordinate function showed that：There were no significant differences among drought resistances of varieties and provenances. The change of physiological indices in different varieties showed differ-ent ranges. The drought resistance of seven varieties decreased in order as fol ows：Koroneiki〉 Picual〉 Berat〉 Kaliniot〉 Frantoio〉 Coratina〉 Arbequina.

Effects of EMS Treatment on Leaf Regeneration and Heat Tolerance of Tissue-cultured Rhododendron chrysanthum Pall. Seedlings

With tissue cultured-seedlings of Rhododendron chrysanthum Pall. in Changbai Mountain as test material, the effect of EMS treatment on the heat toler- ance of R. chrysanthum, as well as the possible heat tolerance mechanism, was in- vestigated in this study so as to lay a foundation for the popularization, application and germplasm resource innovation of R. chrysanthum. The results showed that when the leaves of the tissue cultured seedlings were treated with medium with 0.1% of EMS for 2 d, the survival rate of the leaves was 48.92%, thus the con- centration of EMS was close to the semi-lethal dose, and the EMS concentration and treatment time could be used as screening conditions for heat-tolerant mutants. The plantlets regenerated from EMS-treated leaves were treated with different tem- peratures, and related physiological indicators were determined. The results showed that the chlorophyll content, MDA content, Pro content, SOD activity, POD activity and soluble sugar content of regeneration plantlets in the treatment group were sig- nificantly different from those in the control group. At the same temperature, the chlorophyll content, soluble sugar content, Pro content, SOD activity and POD ac- tivity were significantly higher and the MDA content was significantly lower in the treatment group compared with the control. In conclusion, EMS treatment improved the heat tolerance of tissue-cultured R. chrysanthum seedlings.

Effects of elevated CO_2 concentration on growth and water usage of tomato seedlings under different ammonium/nitrate ratios

Increasing atmospheric CO2 concentration is generally expected to enhance photosynthesis and growth of agricultural C3 vegetable crops, and therefore results in an increase in crop yield. However, little is known about the combined effect of elevated CO2 and N species on plant growth and development. Two growth-chamber experiments were conducted to determine the effects of NH4^＋/NO3^- ratio and elevated CO2 concentration on the physiological development and water use of tomato seedlings. Tomato was grown for 45 d in containers with nutrient solutions varying in NH4^＋/NO3^- ratios and CO2 concentrations in growth chambers. Results showed that plant height, stem thickness, total dry weight, dry weight of the leaves, stems and roots, G value （total plant dry weight/seedling days）, chlorophyll content, photosynthetic rate, leaf-level and whole plant-level water use efficiency and cumulative water consumption of tomato seedlings were increased with increasing proportion of NO3- in nutrient solutions in the elevated CO2 treatment. Plant biomass, plant height, stem thickness and photosynthetic rate were 67%, 22%, 24% and 55% higher at elevated CO2 concentration than at ambient CO2 concentration, depending on the values of NH4^＋/NO3^- ratio. These results indicated that elevating CO2 concentration did not mitigate the adverse effects of 100% NH4^＋-N （in nutrient solution） on the tomato seedlings. At both CO2 levels, NH4^＋/NO3^- ratios of nutrient solutions strongly influenced almost every measure of plant performance, and nitrate-fed plants attained a greater biomass production, as compared to ammonium-fed plants. These phenomena seem to be related to the coordinated regulation of photosynthetic rate and cumulative water consumption of tomato seedlings.