Exogenous calcium enhances the physiological status and photosynthetic capacity of rose under drought stress

Drought(water shortage)can substantially limit the yield and economic value of rose plants(Rosa spp.).Here,we characterized the effect of exogenous calcium(Ca^(2+))on the antioxidant system and photosynthesis-related properties of rose under polyethylene glycol 6000(PEG6000)-induced drought stress.Chlorophyll levels,as well as leaf and root biomass,were significantly reduced by drought;drought also had a major effect on the enzymatic antioxidant system and increased concentrations of reactive oxygen species.Application of exogenous Ca^(2+)increased the net photosynthetic rate and stomatal conductance of leaves,enhanced water-use efficiency,and increased the length and width of stomata following exposure to drought.Organ-specific physiological responses were observed under different concentrations of Ca^(2+).Application of 5 mmol·L^(-1)Ca^(2+)promoted photosynthesis and antioxidant activity in the leaves,and application of 10 mmol·L^(-1)Ca^(2+)promoted antioxidant activity in the roots.Application of exogenous Ca^(2+)greatly enhanced the phenotype and photosynthetic capacity of potted rose plants following exposure to drought stress.Overall,our findings indicate that the application of exogenous Ca^(2+)enhances the drought resistance of roses by promoting physiological adaptation and that it could be used to aid the cultivation of rose plants.

Physiological Mechanism of Exogenous Selenium in Alleviating Mercury Stress on Pakchoi(Brassica campestris L.)

The objective of this study was to explain the physiological mechanisms through which Na_(2)SeO_(3) mitigates the growth and developmental inhibition of pakchoi under HgCl_(2)stress.The results showed that treatment with HgCl_(2)(40 mg L^(−1))led to reduced biomass,dwarfing,root shortening,and root tip necrosis in pakchoi.Compared to control(CK),the activities of superoxide dismutase(SOD)and peroxidase(POD)in Hg treatment increased,and the content of malondialdehyde(MDA)also dramatically increased,which negatively impacted the growth of pakchoi.Low concentrations of Na_(2)SeO_(3)(0.2 mg L^(−1))significantly increased the content of soluble sugars compared with control,while chlorophyll,soluble proteins,free amino acids,and vitamin C had no significant changes.The results of the mixed treatments with HgCl_(2)and Na_(2)SeO_(3) suggested that selenium may be able to reduce the toxicity of mercury in pakchoi.The biomass,plant height,root length,chlorophyll content,soluble protein,other physiological indicators,and proline showed significant increases compared with the HgCl_(2)treatment.Additionally,the MDA content and mercury accumulation in pakchoi decreased.Our results revealed the antagonistic effects of selenium and mercury in pakchoi.Thus,a theoretical basis for studying pakchoi’s mercuryexcreted and selenium-rich cultivation technology was provided.

Physiological Response Mechanism and Drought Resistance Evaluation of Passiflora edulis Sims under Drought Stress

In order to explore the response mechanism of Passiflora edulis Sims to drought stress,the changes in morpho-logical and physiological traits of Passiflora edulis Sims under different drought conditions were studied.A total of 7 germplasm resources of Passiflora edulis Sims were selected and tested under drought stress by the pot culture method under 4 treatment levels:75%–80%(Control,CK)of maximumfield water capacity,55%–60%(Light Drought,LD)of maximumfield water capacity,i.e.,mild drought,40%–45%(Moderate Drought,MD)of max-imumfield water capacity,i.e.,moderate drought and 30%–35%(Severe Drought,SD)of maximumfield water capacity,i.e.,severe drought.On the 40th day of drought treatment,13 indices,including seedling growth mor-phology,physiology,and biochemistry,were measured.The results showed that under drought stress,the height and ground diameter of P.edulis Sims gradually decreased with increasing drought stress,and there were signifi-cant differences in seedling height and ground diameter among the treatments.Drought stress significantly inhib-ited the growth of seven P.edulis Sims varieties.The contents of soluble sugar(SS),soluble protein(SP),proline(Pro),and other substances in P.edulis Sims basically increased with increasing drought stress.With the aggrava-tion of drought stress,the malondialdehyde(MDA)content of P.edulis Sims tended to increase to different degrees,the superoxide dismutase(SOD)activity and peroxidase(POD)activity both tended to increase atfirst and then decrease,and the change in catalase(CAT)activity mostly showed a gradual increasing trend.The con-tents of endogenous hormones in P.edulis Sims significantly differed under different degrees of drought stress.With the aggravation of drought stress,the abscisic acid(ABA)content of P.edulis Sims tended to increase,whereas the contents of gibberellin(GA),indoleacetic acid(IAA),and zeatin nucleoside(ZR)exhibited a down-ward trend.A comprehensive evaluation of the drought resistance of seven P.edulis Sims varieties was conducted based on the principal component analysis method,and the results showed that the drought resistance decreased in the order XH-BL>XH-TWZ>TN1>GH1>ZJ-MT>LP-LZ>DH-JW.

Effects of Low Temperature Stress on Physiological and Biochemical Characteristics of Podocarpus nagi

[Objective] The paper was to study the effect of low temperature stress on physiological and biochemical characteristics of Podocarpus nagi. [Method] Through the determination of physiological indices such as plasma membrane permeability, free proline content, soluble sugar content, malondialdehyde （MDA） content and chlorophyll content, the change law of these indices of P. nagi seedlings under natural conditions and artificially controlled low temperature conditions within the continuous 5 d was studied. [Result] The soluble sugar content, free proline content, MDA content and plasma membrane permeability of P. nagi seedlings were slightly in- creased compared with control; the chlorophyll content gradually decreased with the prolongation of low temperature stress. P. nagi seedlings produced active response to low temperature stress, so the low temperature injury P. nagi seedlings suffered was reduced. [Conclusion] The study provided theoretical basis for winter management in P. nagi cultivation in Hanjiang plain area.

Effect of Cold Stress on Some Physiological Indexes of Plants in Malvaceae

The paper was to study the change trend of the physiological indexes in plants of Malvaceae under normal and low temperature condition.The result showed that the increase extent of electrical conductivity of plants with cold tolerance in Malvaceae was significantly lower than the plant without cold tolerance under the cold stress condition,while their proline contents and soluble protein contents were all higher than the plants without cold tolerance.The above physiological indicators all can be used for the screening of varieties with cold tolerance in Malvaceae,which will also provide theoretical guidance for the cold tolerance screening of other garden plants.

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.

Physiological and Biochemical Responses of Grape Yinhong Seedlings to Short-term Weaklight Stress

The plant growth and physiological and biochemical responses of root and leaves of grape Yinhong seedlings to the weak lights of 20 000,16 000,12 000,8 000 lx and the normal illumination of 25 000 lx（CK） respectively,were investigated.There was no significant dfference in growth indexes of root and leaves of grapevine seedlings between the light of 20 000 lx and CK,and the light of 16 000 lx and CK for 30 d.The chlorophyll contents,soluble protein contents,net photosynthetic rates,transpiration rates,stomatal conductance,water use efficiency and protective enzyme（CAT,POD,SOD） activities in the leaves under the lights of 20 000 lx and 16 000 lx for 30 d were all higher than those under the lights of 20 000 lx and 16 000 lx for 1 d.Under the light of 8 000 lx for 30 d,the growth indexes of root and leaves of grapevine seedlings were significantly lower than those of CK,and except for MDA content,most physiological and biochemical indexes of the leaves were significantly lower than those under the light of 8 000 lx for 1 d.Under12 000 lx,the values of most growth indexes in root and leaves and physiological and biochemical indexes in leaves were between the 16 000 lx and 8 000 lx.In conclusion,Yinhong could grow under the lights above 16 000 lx,and would be stunted by the weak light below 8 000 lx.

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.

Influences of Na_2CO_3 Stress on Physiological Metabolisms of Different Alkali Tolerant Varieties of Stevia rebaudiana

[Objective] The research aimed to reveal physiological mechanisms of alkali tolerances of different Stevia rebaudiana varieties under alkali stress.[Method] By using matrix culture method,the influences of Na2CO3 on chlorophyll content,malondialdehyde（MDA）,superoxide dismutase（SOD）,peroxidase（POD） and Proline（Pro） content of leaves from different alkali tolerance varieties of S.rebaudiana [No.2 Shoutian（relative alkali tolerance variety） and No.4 Zhongshan（alkali sensitivity variety）] were studied.[Result] 1.2 g/L of Na2CO3 stress made that the chlorophyll contents of leaves from No.2 Shoutian and No.4 Zhongshan seedlings both decreased in different degrees.Moreover,MDA content of No.4 Zhongshan was higher than control during the whole stress period,and the largest increase amplitude was 43.2%.MDA content of No.2 Shoutian was lower than control in early and latter periods of stress,and increased the maximum on the 14th day of alkali stress,which was 24.4% higher than control.SOD activities of No.2 Shoutian and No.4 Zhongshan both showed a trend of first increasing and declining then in the alkali stress period,but the increasing extent of SOD activity in No.2 Shoutian was higher than that in No.4 Zhongshan.In latter period of Na2CO3 stress,SOD activity of No.2 Shoutian declined,but POD activity was higher than that of No.4 Zhongshan.It illustrated that POD had stronger scavenging capability of active oxygen.Pro contents of No.2 Shoutian and No.4 Zhongshan were higher than control in the stress period.It showed that the osmoregulation of Pro might not be key regulatory factor of alkali tolerance difference of the two S.rebaudiana varieties.[Conclusion] The research not only provided theoretical basis for further breeding new salt tolerance variety of S.rebaudiana,but also had important significance for improving utilized ratio of kaline soil and growing environment for mudflat in China.

Effects of Pyrene Stress on Growth and Physiological Indexes of Maize(Zea mays L.) Seedling

[Objective]The paper was to explore the effects of pyrene stress on growth and physiological indexes of maize seedling.[Method] The effects of different concentrations of pyrene（0,0.5,1.0,and 2.0 mg/L） on growth and several physiological indexes,such as chlorophyll content,malnodiadehyde（MDA） content of both leaves and roots of maize（Zea Mays L.） seedlings of Shixiang 1（sensitive variety） and Guangtian 3（tolerant variety） were studied by a hydroponic experiment.[Result]As the concentration of prene increasing within the test concentration range,the contents of chlorophyll a and chlorophyll b in Shixiang 1 first increased and then decreased;relative growth yield and absolute growth rate showed the decreasing trend;MDA contents in roots and leaves showed the increasing trend.Relative growth yield,absolute growth rate and chlorophyll a content in Guangtian 3 first increased and then decreased;chlorophyll b and MDA contents in roots showed the increasing trend;MDA contents in leaves showed the decreasing trend.Compared with control,chlorophyll a and chlorophyll b contents of Shixiang 1 significantly increased under pyrene concentration of 0.5-1.0 mg/L,which significantly decreased as the concentration of pyrene ≥2.0 mg/L;MDA contents in roots and leaves significantly increased as the concentration of pyrene ≥1.0 mg/L,while relative growth yield and absolute growth rate significantly decreased.Chlorophyll a and chlorophyll b contents in Guangtian 3 significantly increased as the concentration of pyrene ≥1.0 mg/L.Pyrene concentration had significantly negative correlation with relative growth yield and absolute growth rate of Shixiang 1,while it had significant positive correlation with MDA contents in roots.Pyrene concentration had significant positive correlation with chlorophyll b and MDA contents in roots of tolerant variety Guangtian 3.[Conclusion]The study provided basis for the management measures of maize during its seedling stage.

Effect of Lead Stress on Growth Characteristics and Physiological Indexes of Alternanthera philoxeroides

[Objective] The paper aimed to discuss effects of different concentrations of lead stress on Alternanthera philoxeroides growth and physiological indices,to explore phytoremediation methods for removal of lead pollution. [Method] A. philoxeroides in water culture was treated with different concentration of lead,and then,its external injury was observed,its growth and physiological indexes were measured. [Result] A. philoxeroides biomass and chlorophyll content decreased; conductivity and malonaldehyde （MDA ） content were increased; the SOD,POD and CAT activities showed a trend of first increase and then decrease with increase in concentration of lead stress. [Conclusion] With increase in lead concentration,the cell membrane permeability increased and MDA had a higher accumulation,antioxidant enzymes activity decreased,the normal oxidative metabolism of A. philoxeroides was severely affected,leading it to wilt.

Effects of Waterlogging Stress on Growth and Physiological Index in Cucumber Seedlings

The effects of waterlogging stress on the growth, chlorophyll and MDA content of cucumber seedlings were studied by using cucumber varieties （Cucumis sativus L. cv. Jinyan No.7） as materials. The results show that plant height, leaf number, shoot fresh weight, total root length, total projected area and total surface area of cucumber seedlings showed insignificant differences with those of the control; root fresh weight, root average diameter, total root volume were significantly higher, but the number of root tips and furcation number increased first and then reduced; the chlorophyll content of cucumber seedlings was significantly lower than that of control; MDA content was significantly higher than that of control under waterlogging stress. It was showed that the cucumber was tolerant to waterlogging stress, but the ability of waterlogging stress was limited, and the physiological was significantly hurt and photosynthesis of cucumber seedlings was significantly affected by waterlogging stress.

Salt Stress Effect on the Growth and Physiological Characteristics of Three New Varieties of Lagerstroemia indica

The effects of different concentrations of NaCI （0, 0.10%, 0.25%, 0.40%, 0.55%, 0.70%） on the growth and physiological characteristics of three new varieties of Lagerstroemia indica were studied by pot experiment in the plastic greenhouses. The results showed that under different NaCI concentrations, the relative height in- crement and the relative diameter increment of L. indica were restrained obviously; the contents of chlorophyll a, chlorophyll b, carotenoid and GSH decreased with in- crease of NaCI concentration; and the content of MDA increased with increase of NaCI concentration. Through the determination and comparison of physiological in- dexes, and analysis of correlativity, NaCI tolerance of the three new L. indica vari- eties ranked as L. indica ＇Pink Velour＇〉L. indica ＇Dynamite＇〉L. indica ＇Red Rock- et＇. This is consistent with the results of the morphological characteristics after Na- CI stress.

Effect of Different Kinds of Growth-promoting Rhizobacteria on Physiological and Biochemical Characteristics of Medicago sative Linn. Seedlings under the Stress of Na_2CO_3

[Objective] The study aimed to explore the influences of Plant growth-promoting rhizobacteria（PGPR）on salt tolerance and physiological effect of seedlings of Medicago sative L.[Method] Three different kinds of growth-promoting rhizobacteria solutions were used to spray on M.sative seedlings and the influences of different kinds of growth-promoting rhizobacteria on physiological and biochemical characteristics of M.sative seedlings under 75 mmol/L of Na2CO3 were studied.[Results] Compared with the control group,the chlorophyll,free proline,soluble sugar and soluble protein content of M.sative seedlings treated with different kinds of growth-promoting rhizobacteria were increased,while the effect of CS3 treatment was the best.[Conclusion] The growth-promoting rhizobacteria could promote growth and development of M.sative as well as increased its resistance.

Changes in Physiological Indexes of SPDS Transgenic Potato Plants under Low Temperature Stress

Using potato plants overexpressing spermidine synthase（SPDS） gene as experimental materials, changes in chlorophyll content, malondialdehyde（MDA） content and superoxide dismutase（SOD） activity of potato leaves under low temperature stress were determined. According to the results, chlorophyll content of experimental plants showed a decreasing trend; MDA content of 01-47 was significantly higher than that of Atlantic; MDA content of 01-6 and 01-49 was significantly lower than that of Atlantic; SOD activity of 01-6 and 01-47 was higher than that of Atlantic. Potato lines 01-6 and 01-47 can be further cultivated to breed new cold-resistant potato varieties.

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.

Influence of Water Stress on the Physiological and Biochemical Characteristics of Scutellaria Baicalensis Georgi

Previous studies have shown that water stress can stimulate biosynthesis of secondary metabolites,and physiological and biochemical characteristics of plant can play a key role in its defense responses to water stress.So the physiological and biochemical characteristics of potted Scutellaria baicalensis Georgi plants were investigated under continuous water stress condition.The results showed that the water content in roots,stems and leaves,together with chlorophyll content of the leaves decreased as the water stress strengthened.Simultaneously,the specific leaf weight increased,and the content of proline and soluble sugar in Scutellaria baicalensis Georgi leaves increased significantly.The changing trends of the baicalin content in the roots,stems and leaves of Scutellaria baicalensis Georgi were different.It increased continuously in roots,while ascended constantly in the stems and leaves during the early days under the water stress,but decreased sharply under the heavy stress.In conclusion,proline and soluble sugar had a close correlation with the drought resistance of Scutellaria baicalensis Georgi.Moderate drought is in favor of synthesizing the secondary metabolites.

Physiological and molecular responses to cold stress in rapeseed(Brassica napus L.)

Low temperature is one of the most important abiotic factors inhibiting growth, productivity, and distribution of rapeseed(Brassica napus L.). Therefore, it is important to identify and cultivate cold-tolerant germplasm. The objective of this study was to figure out the mechanism of chilling(4 and 2°C) and freezing(–2 and –4°C) stresses along with a control(22°C) in B. napus cultivars(1801 and C20) under controlled environment(growth chamber). The experiment was arranged in a complete randomized design with three replications. Our results exhibited that under chilling and freezing stresses, the increment of proline accumulation, soluble sugar and protein contents, and antioxidant enzyme activity were enhanced more in 1801 cultivar compared with C20 cultivar. At –2 and –4°C, the seedlings of C20 cultivar died completely compared with 1801 cultivar. Hydrogen peroxide(H2 O2) and malondialdehyde contents(MDA) increased in both cultivars, but when the temperature was decreased up to –2 and –4°C, the MDA and H2 O2 contents continuously dropped in 1801 cultivar. Moreover, we found that leaf abscisic acid(ABA) was enhanced in 1801 cultivar under chilling and freezing stresses. Additionally, the transcriptional regulations of cold-tolerant genes(COLD1, CBF4, COR6.6, COR15, and COR25) were also determined using real-time quantitative PCR(RT-q PCR). RT-q PCR showed that higher expression of these genes were found in 1801 as compared to C20 under cold stress(chilling and freezing stresses). Therefore, it is concluded from this experiment that 1801 cultivar has a higher ability to respond to cold stress(chilling and freezing stresses) by maintaining hormonal, antioxidative, and osmotic activity along with gene transcription process than C20. The result of this study will provide a solid foundation for understanding physiological and molecular mechanisms of cold stress signaling in rapeseed(B. napus).

Growth and physiological responses of Agriophyllum squarrosum to sand burial stress

Agriophyllum squarrosum is an annual desert plant widely distributed on mobile and semi-mobile dunes in all the sandy deserts of China. We studied the growth and physiological properties of A. squarrosum seedlings under different sand burial depths in 2010 and 2011 at Horqin Sandy Land, Inner Mongolia to understand the ability and mechanism that A. squarrosum withstands sand burial. The results showed that A. squarrosum had a strong ability to withstand sand burial. Its survival rate, plant height and biomass increased significantly at a burial depth 25% of seedling height and decreased significantly only when the burial depth exceeded the height of the seedlings; some plants still survived even if the burial depth reached 266% of a seedling height. The malondialdehyde （MDA） content and membrane permeability of the plant did not change significantly as long as the burial depth was not greater than the seedling height; lipid peroxidation increased and cell membranes were damaged if the burial depth was increased further. When subjected to sand burial stress, superoxide dismutase （SOD） and peroxidase （POD） activities and free proline content increased in the seedlings, while the catalase （CAT） activity and soluble sugar content decreased. Sand burial did not lead to water stress. Reductions in photosynthetic area and cell membrane damage caused by sand burial may be the major mechanisms increasing mortality and inhibiting growth of the seedling. But the increases in SOD and POD activities and proline content must play a certain role in reducing sand burial damage.

Effects of Phosphate Fertilizer on Cold Tolerance and Its Related Physiological Parameters in Rice Under Low Temperature Stress

The study was designated to explore the physiological mechanism of cold tolerance enhanced by phosphate in rice. An experiment was conducted to investigate the effects of different levels of phosphate fertilizer on cold tolerance and its related physiological parameters in rice seedings （chilling-sensitive cv. Changbai 9 and chilling-tolerant cv. Jijing 81） under low temperature stress. At the same time, the identification of cold tolerance was conducted. Compared with the normal temperature treatment, the relative chlorophyll content, photosynthesis rate, Fv/Fm and qP decreased and index of unsaturated fatty acid increased in rice under low temperature stress. The effect of chilling-sensitive cultivars was more than that of chilling-tolerant cultivars, more phosphorus fertilizer properly improved seedling quality of rice, slowed relative chlorophyll content dropping degree of rice seeding, increased photosynthesis rate, Fv/Fm, qP and index of unsaturated fatty acids, and enhanced the ability to chilling-tolerant cultivars under low temperature. The effect on chilling-tolerant cultivars was significantly higher than that on chilling sensitive cultivars by applying more phosphorus fertilizer. Phosphate regulated photosynthetic physiology and membrane fluidity to reduce injury by low temperature, and increasd the cold tolerance capacity of rice.