Relative Membrane Permeability Research Articles

Roots play a vital role in flood-tolerance of poplar demonstrated by reciprocal grafting

Poplar is one of the most important multipurpose afforestation trees in river floodplains and arable farmland which are subject to frequent flooding. To determine the relative roles that the roots and shoots have in responses to waterlogging, six root-shoot grafting combinations of full-sib poplar clones LS1 (flood-tolerant) and LS2 (flood-susceptible) were compared for waterlogging effects on them, using reciprocal and self-grafts. Plants of the six combinations comprised non-grafted (LS1) and (LS2), self-grafted (LS1/LS1) and (LS2/LS2), LS1 grafted onto LS2 (LS1/LS2), and LS2 grafted onto LS1 (LS2/LS1) experimental plants. The two clones LS1 and LS2 originated from Populus deltoides cv. Lux ex. I-69/55 (flood-tolerant)×P. simonii (flood-susceptible). Growth, morphological and ecophysiological parameters of plants belonging to the six grafting combinations were subjected for 21 days to flooding, followed by a six-day drainage and recovery stage. Results showed that flooding stress affected adversely growth, biomass accumulation, morphological and ecophysiological characteristics in all flooded plants. The more severe influences were found in the plants with LS2 roots (LS1/LS2, LS2/LS2, LS2), whereas plants having roots of LS1 (LS2/LS1, LS1/LS1, LS1) were less negatively affected. At the end of the study, 100%, 100%, 93.3%, 26.7%, 6.7% and 20% survival rates, respectively, were observed in flooded plants of LS1, LS1/LS1, LS2/LS1, LS1/LS2, LS2/LS2 and LS2. In conformity with the results for growth, biomass accumulation and morphology, responses to flooding of gas exchange, chlorophyll fluorescence, relative membrane permeability of leaves, the overall root metabolism parameter dehydrogenase activity (TTC assay), as well as malonaldehyde contents of leaves and roots also indicated that flood injury was significantly more pronounced in plants having LS2 roots than in those with LS1 roots. Plants with roots of LS1 displayed clearly faster recovery after flooding than the plants with LS2 roots. The results indicate that flooding-tolerance of poplar is based more on influences from the rootstock than on those of the scion. It is thus the root genotype that plays the decisive role in flood-tolerance of poplar.

Overexpression of GsZFP1 enhances salt and drought tolerance in transgenic alfalfa (Medicago sativa L.)

GsZFP1 encodes a Cys2/His2-type zinc-finger protein. In our previous study, when GsZFP1 was heterologously expressed in Arabidopsis, the transgenic Arabidopsis plants exhibited enhanced drought and cold tolerance. However, it is still unknown whether GsZFP1 is also involved in salt stress. GsZFP1 is from the wild legume Glycine soja. Therefore, the aims of this study were to further elucidate the functions of the GsZFP1 gene under salt and drought stress in the forage legume alfalfa and to investigate its biochemical and physiological functions under these stress conditions. Our data showed that overexpression of GsZFP1 in alfalfa resulted in enhanced salt tolerance. Under high salinity stress, greater relative membrane permeability and malondialdehyde (MDA) content were observed and more free proline and soluble sugars accumulated in transgenic alfalfa than in the wild-type (WT) plants; in addition, the transgenic lines accumulated less Na(+) and more K(+) in both the shoots and roots. Overexpression of GsZFP1 also enhanced the drought tolerance of alfalfa. The fold-inductions of stress-responsive marker gene expression, including MtCOR47, MtRAB18, MtP5CS, and MtRD2, were greater in transgenic alfalfa than those of WT under drought stress conditions. In conclusion, the transgenic alfalfa plants generated in this study could be used for farming in salt-affected as well as arid and semi-arid areas.

Biochemical characterization of maize (Zea mays L.) for salt tolerance

The inherent differences for salt tolerance in two maize cultivars (Agatti-2002 and Sahiwal-2002) were evaluated in pot experiments. Plants were grown in half-strength of Hoagland nutrient solution added with 0, 80, 100, 120, 140 and 160 mM of NaCl. Salt stress markedly reduced the shoot and root lengths and fresh and dry masses. Reduction in growth attributes was more pronounced in cv. Agatti-2002 than cv. Sahiwal-2002. Both maize cultivars exhibited significant perturbations in important biochemical attributes being employed for screening the crops for salt tolerance. Cultivar Sahiwal-2002 was found salt tolerant as compared to cv. Agatti-2002 because it exhibited lower levels of H2O2, malondialdehyde (MDA) and higher activities of antioxidant enzymes. In addition, cultivar Sahiwal-2002 exhibited less salt-induced degradation of photosynthetic pigments, lower levels of toxic Na+ and Cl− and higher endogenous levels of K+ and K+/Na+ ratio. The results indicate that salt stress induced a marked increase in MDA, H2O2, relative membrane permeability, total soluble proteins and activities of antioxidant enzymes (superoxide dismutase, peroxidase, catalase andascorbate peroxidase). Moreover, increase in endogenous levels of Na+ and Cl− and decrease in K+ and K+/Na+ ratio and photosynthetic pigments were recorded in plants grown under salinity regimes.

An assessment of Agropyron cristatum tolerance to cadmium contaminated soil

A pot experiment was conducted in a greenhouse to assess the tolerance of Agropyron cristatum plants to cadmium contaminated soils (0, 5, 10, 25, 50, 100, 150, and 200 mg kg−1) for 100 d. Results indicate that Cd in concentrations of 5–50 mg kg−1 had no significant impact on growth, relative membrane permeability (RMP), lipid peroxidation measured as malondialdehyde (MDA) content, and chlorophyll (Chl) content relative to the control. Exposure of these plants to high concentrations of Cd (100–200 mg kg−1) caused a small reduction in growth and Chl content and a slight enhancement of RMP and MDA content compared with the control. In addition, superoxide dismutase (SOD) and peroxidase (POD) activities show an increasing trend with the increase of Cd content in soil. The Cd content in the roots was 4.7–6.1 times higher than that in the shoots under all Cd treatments suggesting that the plant can be classified as a Cd excluder. The translocation factor was low and similar at 25–200 mg kg−1 Cd treatments. In summary, A. cristatum plants tolerated Cd stress and might have potential for the phytoremediation of Cd contaminated soils.

Response of Maize Seedlings to Cadmium Application after Different Time Intervals

Present study was conducted to appraise the inhibitory effects of cadmium applied at different time intervals on various growth and biochemical parameters in two maize lines, Maize-TargetedMutagenesis 1 and 2 (MTM-1 and MTM-2). Twenty-day-old seedlings were exposed to 0, 3, 6, 9, and 12 mg CdCl2kg−1sand. Both maize lines exhibited significant perturbations in important biochemical attributes being employed for screening the crops for cadmium tolerance. The results showed that a higher concentration of cadmium (12 mg CdCl2kg−1) considerably reduced the plant growth in line MTM-1 on the 5th, 10th, and 15th day after the treatment. In contrast, irrespective of exposure time, the plant biomass and leaf area did not show inhibitory effects of cadmium, specifically at 3 mg CdCl2kg−1in line MTM-2. In addition, MTM-2 was found to be more tolerant than line MTM-1 in terms of lower levels of hydrogen peroxide (H2O2), malondialdehyde (MDA) contents, and relative membrane permeability (RMP). Moreover, H2O2, MDA, RMP, and anthocyanin increased at all levels of cadmium in both lines, but a significant decline was observed in photosynthetic pigments, total free amino acids, and proline contents in all treatments particularly on the 10th and 15th day after treatment.

Transgenic Alfalfa with GsPPCK1 and Its Alkaline Tolerance Analysis

Environmental stresses, such as drought, high salty and alkali, adversely affect plant growth and productivity. Plants adapt to these environmental stresses by inducing numerous genes at the transcriptional level and by protein phosphorylation. Phosphoenolpyruvate carboxylase kinase (PPCK) is a Ca2+ independent kinase in response to a range of signals in different plant tissues which plays a key role in the control of plant metabolism. As an important extension of our earlier studies summarized above on global transcriptome profiling of wild soybean under NaHCO3 treatment, an alkaline (NaHCO3) related gene GsPPCK1 was identified and subsequently cloned from Glycine soja, which has 99% similarity with PPCK1 of Glycine max (AAQ83695.1), named as GsPPCK1. Expression of GsPPCK1 mRNA was induced by NaHCO3 stress in roots and leaves. GsPPCK1 transcripts increased during 3 hour exposures to NaHCO3 stress. These results indicated that wild soybean PPCK1 was an early responded gene to alkaline stress. We transformed GsPPCK1 gene into alfalfa using a developed method, and transgenic alfalfa showed observably enhanced tolerance to NaHCO3 stress compared with wild-type plants. Transgenic alfalfa grew well in the conditions of 100 mmol L–1 NaHCO3 , while wild type plants exhibited discoloration and stunted growth, or even death. There were significantly changes in malondialdehyde content and relative membrane permeability caused by saline-alkaline stress in non-transgenic lines compared to transgenic lines (P0.05). Moreover, compared with non-transgenic, transgenic alfalfa had higher levels of chlorophyll content and root activity under alkali stress conditions. The result indicated that over-expression of GsPPCK1 in alfalfa could enhance alkaline tolerance. All results showed that GsPPCK1 gene could improve the tolerance of transgenic alfalfa to alkali stress; therefore, the study on this field is of significance not only in theory but also in practice.

Salt-induced changes in the growth, key physicochemical and biochemical parameters, enzyme activities, and levels of non-enzymatic anti-oxidants in cauliflower (Brassica oleracea L.)

SummarySalt-induced changes in the growth, leaf chlorophyll contents, water relations, inorganic nutrient contents, activities of some anti-oxidant enzymes, and levels of non-enzymatic anti-oxidants in cauliflower (Brassica oleracea L.) were examined under greenhouse conditions. Fifteen-day-old seedlings of two cultivars of cauliflower (‘FD1’ and ‘FD2’) were exposed to four different levels of saline stress [0 (control), 50, 100, or 150 mM NaCl] for 30 d, applied through the rooting medium. Increasing levels of NaCl significantly decreased shoot and root dry weights (DWs), relative water contents (RWC), leaf and root K+ ion contents, total soluble proteins, total phenolic compounds, malondialdehyde (MDA) levels, and root K+/Na+ and Ca2+/Na+ ratios. Increasing salinity increased leaf water contents, leaf and root Na+ and Cl– ion contents, leaf free proline, glycinebetaine (GB), and ascorbic acid (AsA) contents, as well as the activities of superoxide dismutase (SOD), peroxidase (POX), and catalase (CAT) in both cauliflower cultivars. However, no significant effects of NaCl were observed on chlorophyll a and b contents, relative membrane permeability (RMP), and leaf or root Ca2+ ion contents in either cauliflower cultivar. ‘FD2’ was relatively less-affected by salt stress. The relatively improved growth performance of ‘FD2’ under saline conditions was found to be attributable to its higher RWC, as well as increased levels of proline, root Ca2+ ions, total phenolic compounds and AsA, as well as elevated SOD activity, and lower levels of MDA compared to ‘FD1’ plants under salt stress.

Role of polyamines and phospholipase D in maize (Zea mays L.) response to drought stress

An in vitro experiment was conducted to elucidate the role of polyamines and phospholipase D (PLD) in maize (Zea mays L.) response to drought stress simulated by PEG-6000. During the early stage of drought stress, an increase of PLD activity played a major role in stomatal closure as an adaptive response to drought stress and this process was independent of polyamine synthesis. Under prolonged drought stress, the total content of polyamines including putrescine (Put), spermidine (Spd) and spermine (Spm) increased at 120min after drought stress treatment while the ratio of Spd+Spm/Put decreased, which caused an increase in PLD activity, relative membrane permeability and malondialdehyde content (MDA). Exogenous polyamines enhanced PLD activity, and the greatest effect was induced by Put. Therefore, we concluded that PLD played an important role in mitigation of drought stress damage in the early stage of drought stress which was independent of polyamine accumulation. However, in the later stage of drought stress, the obvious elevation of PLD activity led to serious membrane damage regulated by the ratio of Spd+Spm/Put.

Over-expressing GsGST14 from Glycine soja enhances alkaline tolerance of transgenic Medicago sativa

Glutathione-S-transferases (GSTs) are ubiquitous enzymes that play a key role in stress tolerance and cellular detoxification. The GST gene GsGST14 selected from the gene expression profiles of Glycine soja under alkaline stress was transformed into alfalfa (Medicago sativa L.). Transgenic alfalfa plants showed 1.73–1.99 times higher GST activity than wild-type plants. Transgenic alfalfa grew well in the presence of 100 mM NaHCO3, while wild-type plants exhibited chlorosis and stunted growth, even death. There were marked changes in malondialdehyde content and relative membrane permeability caused by alkaline stress in non-transgenic lines compared to transgenic lines. The results indicate that the gene GsGST14 could enhance alkaline resistance in transgenic alfalfa.

When it comes to drug discovery not all Gram‐negative bacterial biodefence pathogens are created equal: Burkholderia pseudomallei is different

When it comes to drug discovery not all Gram‐negative bacterial biodefence pathogens are created equal: <i>Burkholderia pseudomallei</i> is different

Over-expressing GsGST14 from Glycine soja enhances alkaline tolerance of transgenic Medicago sativa

Glutathione-S-transferases (GSTs) are ubiquitous enzymes that play a key role in stress tolerance and cellular detoxification. The GST gene GsGST14 selected from the gene expression profiles of Glycine soja under alkaline stress was transformed into alfalfa (Medicago sativa L.). Transgenic alfalfa plants showed 1.73-1.99 times higher GST activity than wild-type plants. Transgenic alfalfa grew well in the presence of 100 mM NaHCO3, while wild-type plants exhibited chlorosis and stunted growth, even death. There were marked changes in malondialdehyde content and relative membrane permeability caused by alkaline stress in non-transgenic lines compared to transgenic lines. The results indicate that the gene GsGST14 could enhance alkaline resistance in transgenic alfalfa.

冬季高温对白三叶越冬和适应春季"倒春寒"的影响

Perennial plants that normally experience dormancy during winter may be subjected to more cycles of freeze-thaw caused by warming winter.We explored the physiological mechanisms of adaptation of white clover,Trifolium repens Linn,to freeze-thaw stress.In late fall of 2009,uniform plots of white clover grown in a natural environment(NE) were covered with a plastic house(pH) to simulate the effect of a warmer winter or left uncovered(control).During the winter and following spring,growth capacity and physiological indices related to resistance to adverse environment were measured in leaves of white clover grown in both conditions.In the winter of 2009,the average temperature ranged from below zero(-10℃) to 7℃ in the NE during which leaves experienced thawing-freezing-thawing-freezing,and above zero(from 1 ℃ to 7 ℃) in the pH where leaves were never frozen.In late fall of 2009,all white clover was of uniform height.But in spring 2010,plants grown in the PH(26 cm) were 3 times taller than those in the NE(8 cm).This difference in height disappeared by June 2010.In winter,the relative membrane permeability,MDA(malondialdehyde),proline,and soluble sugar contents,and the activities of catalase(CAT) and superoxide dismutase(SOD) and peroxidase(POD) increased with decreasing temperature in leaves of white clover grown in both NE and PH.The physiological index values in the white clover grown in the NE experiencing freezing-thaw stress was greater than those in leaves grown in PH(no freezing).In spring,two days after removing the plastic housing,the relative membrane permeability and content of MDA in the leaves of white clover rose quickly to 127% of values before removing the PH,and even higher than that in the leaves of white clover grown in the NE.Activities of SOD and CAT in white clover after removing the PH also increased quickly to 33% and 84.6% higher than in white clover grown in NE.In addition,during late spring coldness,plants in both treatments showed the same trend of increasing proline and soluble sugar content and activities of POD and SOD in response to lower temperature.Our results suggest that Trifolium repens has a high capacity to activate antioxidant enzyme activity to control lipid peroxidation and increase osmolytes in response to freezing temperature and that these mechanisms play a key role in surviving warm winter.While a warming winter delays the greening period,it does not retard white clover growth in spring,making white clover an excellent plant to withstand climate changes that include warmer winters.

He‐Ne Laser‐Induced Improvement in Biochemical, Physiological, Growth and Yield Characteristics in Sunflower (Helianthus annuus L.)

The water-soaked seeds of sunflower were exposed to low power continuous wave He-Ne laser irradiation of energies 0, 100, 300 and 500 mJ to evaluate the effect on various biochemical, physiological, growth and yield parameters of sunflower. The experiments which consisted of four replicates arranged in a completely randomized design (CRD) were carried out under the greenhouse conditions. The physiological attributes like, photosynthetic rate (A), transpiration rate (E), intrinsic CO(2) concentration (C(i) ), stomatal conductance (g(s)), chlorophyll a and b contents, relative membrane permeability and leaf water (ψ(w)), osmotic (ψ(s)) and turgor (ψ(p)) potentials, relative water contents and leaf area increased significantly as compared to control due to He-Ne treatment of seeds. The activities of superoxide dismutase, peroxidase and catalases and contents of total soluble proteins, malondialdehyde, proline and leaf total phenolic also increased due to laser treatment. Significant increase in growth parameters of sunflower like shoot fresh and dry masses, root fresh and dry masses, root and shoot lengths, number of leaves per plant and stem diameter has also been observed. The contents of K, Ca and Mg in shoot and root were also increased and an overall increase of up to 28.12% was observed due to laser treatment.

PH-responsive polymers for trehalose loading and desiccation protection of human red blood cells

PP-50, a synthetic pH-responsive biopolymer, is here shown to increase the permeability of the phospholipid bilayer to trehalose, a disaccharide accumulated in desiccation tolerant organisms across all kingdoms. Uptake of 251 ± 6 m m intracellular trehalose facilitated an increase in the membrane integrity of vacuum dried cells by a factor of 9 ± 1 and reduced extent of hemoglobin oxidation in dried cells from 66 ± 1% to 23 ± 3%. To elucidate the mechanism of PP-50 mediated trehalose delivery, permeability studies were conducted using molecules ranging in size from sucrose to 10 kDa poly(ethylene glycol). It was shown that the logarithm of relative diffusant membrane permeability decreased linearly with diffusant molecular volume, suggesting transport via non-Stokesian diffusion. Consistent with this conclusion, topographic atomic force micrographs reported membrane thinning proximate to PP-50 adsorption on the erythrocyte membrane, a phenomenon associated with increased incidence of phospholipid hydrocarbon chain bending.

Effect of water stress and re-watering on relative water content, protective enzyme and photosynthetic characteristics of wild jujube

Seedlings relative water content (RWC), tissue water content, water consumption rate, protective enzyme (SOD, POD and CAT) activity, relative membrane permeability, transpiration rate (Tr), photosynthetic rate (Pn) and stomatal conductance (Gs) were analyzed to study the effects of water stress and re-watering on wild jujube. Four treatments, including one circle (Ⅰ), two circles (Ⅱ) and three circles (Ⅲ) water stress/re-watering treatments, and a normal watering (CK) treatment were designed in the experiment. Based on the results, RWC initially decreased, and then stabilized after re-watering. Generally, RWC increased with increasing water stress/re-watering circle after the third day of re-watering. While water consumption rate was highest on the day of re-watering after water stress, tissue water content was lowest on the second day of re-watering. On the second day after re-watering, protective enzyme activities in wild jujube seedlings increased with increasing water stress/re-watering circle. Relative membrane permeability was higher under treatments with lower protective enzyme activity, indicating serious damage of seedling cell membranes. Wild jujube seedling Tr, Pn and Gs after one water stress/re-watering circle were lowest on the day of re-watering. The experiment further showed that wild jujube seedlings became drought resistant after several water stress/re-watering circles. After two or three water stress/re-watering circles, transpiration and photosynthesis in wild jujube seedlings were recovered and drought damage was decreased.

EFFECTS OF PLANT GROWTH PROMOTING BACTERIA ON YIELD, GROWTH, LEAF WATER CONTENT, MEMBRANE PERMEABILITY, AND IONIC COMPOSITION OF STRAWBERRY UNDER SALINE CONDITIONS

Plant growth promoting effects of Bacillus subtilis EY2, Bacillus atrophaeus EY6, Bacillus spharicus GC subgroup B EY30, Staphylococcus kloosii EY37 and Kocuria erythromyxa EY43 were tested on strawberry cv. ‘Fern’ in terms of fruit yield, growth, chlorophyll reading value, leaf relative water content (LRWC), membrane permeability and ionic composition of leaves and roots under saline conditions. Compared with 0 mM sodium chloride (NaCl) treatment, the average decrease of yield and LRWC were 51.6% and 21.0%, respectively, when 35 mM NaCl was applied. However, EY30, EY37, and EY43 treatments under saline condition (35 mM NaCl) significantly increased fruit yield (54.4%, 51.7% and 94.9%) compared with 35 mM NaCl treatment without plant growth promoting bacteria (PGPB). The LRWC increased from 72.0% in 35 mM NaCl treatment to 88.4%, 86.6%, 84.2%, 83.5%, and 86.2% by EY2, EY6, EY30, EY37, and EY43 applications, respectively. The lowest membrane permeability among the bacterial strains was obtained from EY37 treatment (37) while it was 33 and 58 in 0 mM NaCl and 35 mM NaCl treatments, respectively. The concentration of all plant tissue nutrients investigated [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg)] with the exception of root phosphorus (P) and Mg concentration significantly decreased with 35 mM salt treatment. Nitrogen content of leaves varied between 3.04 and 3.14% in bacterial treatments under saline conditions while it was 2.71% in 35 mM NaCl treatment. In contrast sodium (Na) and chloride (Cl) of leaves and Cl content of roots were significantly decreased by root inoculation with all bacterial treatments in comparison to 35 mM NaCl treatment with no inoculation. Treatment with Bacillus EY30, Staphylococcus EY37 and Kocuria EY43 to strawberry plants can ameliorative the deleterious effect of salt stress on fruit yield, growth and nutrition. These results demonstrate that PGPB treatment could be offer an economic and simple means to increased plant resistance for salinity stress.

Salt-induced modulation in growth, photosynthetic capacity, proline content and ion accumulation in sunflower (Helianthus annuus L.)

Salt-induced changes in growth, photosynthetic pigments, various gas exchange characteristics, relative membrane permeability (RMP), relative water content (RWC) and ion accumulation were examined in a greenhouse experiment on eight sunflower (Helianthus annuus L.) cultivars. Sunflower cultivars, namely Hysun-33, Hysun-38, M-3260, S-278, Alstar-Rm, Nstt-160, Mehran-II and Brocar were subjected to non-stress (0 mM NaCl) or salt stress (150 mM NaCl) in sand culture. On the basis of percent reduction in shoot biomass, cvs. Hysun-38 and Nstt-160 were found to be salt tolerant, cvs. Hysun-33, M-3260, S-278 and Mehran-II moderately tolerant and Alstar-Rm and Brocar salt sensitive. Salt stress markedly reduced growth, different gas exchange characteristics such as photosynthetic rate (A), water-use efficiency (WUE) calculated as A/E, transpiration rate (E), internal CO2 concentration (C i) and stomatal conductance (g s) in all cultivars. The effect of 150 mM NaCl stress was non-significant on chlorophyll a and b contents, chlorophyll a/b ratio, RWC, RMP and leaf and root Cl−, K+ and P contents; however, salt stress markedly enhanced C i /C a ratio, free proline content and leaf and root Na+ concentrations in all sunflower cultivars. Of all cultivars, cv. Hysun-38 was higher in gas exchange characteristics, RWC and proline contents as compared with the other cultivars. Overall, none of the earlier-mentioned physiological attributes except leaf K+/Na+ ratio was found to be effective in discriminating the eight sunflower cultivars as the response of each cultivar to salt stress appraised using various physiological attributes was cultivar-specific.

DROUGHT STRESS: Comparative Time Course Action of the Foliar Applied Glycinebetaine, Salicylic Acid, Nitrous Oxide, Brassinosteroids and Spermine in Improving Drought Resistance of Rice

AbstractWorldwide rice productivity is being threatened by increased endeavours of drought stress. Among the visible symptoms of drought stress, hampered water relations and disrupted cellular membrane functions are the most important. Exogenous use of polyamines (PAs), salicylic acid (SA), brassinosteroids (BRs), glycinebetaine (GB) and nitrous oxide (NO) can induce abiotic stresses tolerance in many crops. In this time course study, we appraised the comparative role of all these substances to improve the drought tolerance in rice (Oryza sativa L.) cultivar Super‐Basmati. Plants were subjected to drought stress at four leaf stage (4 weeks after emergence) by maintaining soil moisture at 50 % of field capacity. Pre‐optimized concentrations of GB (150 mg l−1), SA (100 mg l−1), NO (100 μmol l−1 sodium nitroprusside as NO donor), BR (0.01 μm 24‐epibrassinolide) and spermine (Spm; 10 μm) were foliar sprayed at five‐leaf stage (5 weeks after emergence). There were two controls both receiving no foliar spray, viz. well watered (CK1) and drought stressed (CK2). There was substantial reduction in allometric response of rice, gas exchange and water relation attributes by drought stress. While drought stress enhanced the H2O2, malondialdehyde (MDA) and relative membrane permeability, foliar spray of all the chemicals improved growth possibly because of the improved carbon assimilation, enhanced synthesis of metabolites and maintenance of tissue water status. Simultaneous reduction in H2O2 and MDA production was also noted in the plants treated with these substances. Drought tolerance was sturdily associated with the greater tissue water potential, increased synthesis of metabolites and enhanced capacity of antioxidant system. Of all the chemicals, foliar spray with Spm was the most effective followed by BR.

Fresh-keeping effect of natamycin and chitosan compound on of strawberry during storage

The fresh-keeping effects of coating compound using 1% chitosan combined with 0.005%, 0.010%, 0.020%, 0.040% concentration of natamycin respectively on strawberry was investigated, which compared with untreated control and the sample coated with 1% chitosan under normal temperature. The results showed that coating fusion liquid with different concentration of natamycin and 1% chitosan could reduce rate of water loss, delay the decline in contents of soluble solids, vitamin C, total acid, simultaneously, contents of relative membrane permeability, MDA, and increase in polyphenol oxidase (PPO) activities of strawberry fruit were restrained. Of which, coating fusion liqid with 0.020% natamycin and 1% chitosan had better effect on strawberry, with rate of water loss only 7.59% after 7 d, and the high activities of superoxide dismutase(SOD) maintained, senescence of fruit delayed, the storage time of strawberry fruit prolonged.

Effect of paraquat on the antioxidative enzyme activities and lipid peroxidation in opium poppy (Papaver somniferum L.)

Changes of malondialdehyde (MDA) content, the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) in opium poppy, Papaver somniferum were measured at the bud stage treated with different concentrations of paraquat. The results showed that the changing rate of MDA content was the same as that of the cell membrane electrolyte leakage. The MDA content and cell membrane electrolyte leakage decreased in the early stage then increased under 3 ml l–1, 6 ml l–1, 12 ml l–1 treatment. In contrast, the MDA content and relative membrane permeability increased in the early stage then decreased under 24 ml l–1 treatment. Antiox-idant enzyme activities varied under different treatments. SOD activities decreased during 3–24 h and then increased under the 24 ml l–1 treatment. All the peaks of POD activities appeared at the 3 h post treatment. POD activities at the 9 h and the 36 h under 24 ml l–1 treatment were significantly lower than in the control. CAT activities varied under different treatments, increased at 9 h and decreased at 36 h post treatment under 24 ml l–1 treatment. This means that the active oxygen produced in the leaf cells of opium poppy was beyond the recovering capacity of antioxidant enzyme, resulting in the damage of enzyme. These results suggest that a high concentration (24 ml l–1) paraquat treatment caused damages by speeding up the peroxide of the opium poppy plant cells, whereas lower concentrations were less effective.