Heshmat S. Aldesuquy

Kinetin and spermine mediated induction of salt tolerance in wheat plants: Leaf area, photosynthesis and chloroplast ultrastructure of flag leaf at ear emergence

Abstract The antagonistic effects of kinetin and spermine on stress imposed by seawater on leaf area, pigment, Hill reaction, 14CO2 fixation and chloroplast ultrastructure of wheat flag leaf were investigated. Irrigation of wheat plants by seawater at 25% caused marked decrease in leaf area, pigment content, Hill activity and photosynthetic efficiency of wheat flag leaf at ear emergence. Grain priming with kinetin, spermine or their interaction alleviated the adverse effect of seawater stress by stimulating leaf area expansion, pigment production as well as photosynthetic activity. From transmission electron microscopy micrographs, a continuous “end-to-end” distribution of regular (oval or elliptical) chloroplasts around the cells periphery was observed in flag leaf mesophyll cells of control wheat plants. Conversely for seawater-stressed plants, the irregular spherical chloroplasts appeared “bulbous” and discrete, the cells also displayed extensive but thin peripheral cytoplasmic regions devoid of chloroplasts. Grain presoaking in 0.1 mM kinetin caused the chloroplast of stressed wheat plants to be more regular, with organized membrane system, large starch grains and projections in the form of tails. Furthermore, ultrastructure analysis cleared that grain priming with spermine, either alone or in combination with kinetin, caused the chloroplast in flag leaf mesophyll cells of stressed wheat plants to be more regular in shape with more starch grains. The changes in pigment content and photosynthetic activity of flag leaf appeared to depend mainly on chloroplast ultrastructure and its numbers, showing a positive correlation between chloroplasts number and pigment content.

Efficacy of seawater salinity on osmotic adjustment and solutes allocation in wheat (Triticum aestivum) flag leaf during grain filling

ratio in the flag leaves of both cultivars was observed. The capacity of osmotic adjustment was greater in younger leaves than in older ones particularly with higher concentration (25%) in both cultivars. Moreover, the production of both organic and inorganic ions tended to be higher in Sids-1 than in Gemmieza-9. Gemmieza-9 appeared to be more sensitive than Sids-1.Osmotic pressure of flag leaf sap appeared to depend mainly on proline, TSN, TSS, organic acids, glycerol and ions content, where there is a positive correlation between osmotic pressure and all of them.

Impact of osmotic stress on seedling growth observations, membrane characteristics and antioxidant defense system of different wheat genotypes

Abstract The objective of the present study was to find out a straightforward technique for screening the tolerance of ten wheat genotypes to two levels of osmotic stress at early seedling stage. Data revealed that polyethylene glycol-induced drought had general negative effect on seedling morphological characters indicated by plumule and radicle length, number of adventitious roots as well as seedling biomass and water content. Water deficit could also suppress membrane integrity by stimulating lipid peroxidation with marked increase in membrane leakage and subsequent decrease in its stability index. For all the addressed germination parameters and seedling membrane features, the impact of severe drought was more pronounced than that of moderate drought. Simultaneously, moderate stress could activate peroxidase, polyphenol oxidase and ascorbic peroxidase of the studied genotypes; but these enzymes were inhibited by severe stress. The activity of catalase, superoxide dismutase and glutathione reductase was conversely retarded by drought whether at moderate or severe level. More interestingly, a novel function “Stress Impact Index; SII” was introduced to rank the estimated morpho-physiological traits (SIItrait) as well as the considered genotypes (SIIgenotype) according to their sensitivity to stress. Values of SIItrait implied that germination parameters were generally affected by drought more intensively than membrane characteristics and finally came the antioxidant enzymes with the least degree of suppression when applying stress. Based on the magnitudes of SIIgenotype, Sids 13 seemed to be the most drought-tolerant wheat cultivar while Shandawel 1 could be the most sensitive one at their juvenile growth stage.

Exogenous Salicylic Acid and Trehalose Ameliorate Short Term Drought Stress in Wheat Cultivars by Up-regulating Membrane Characteristics and AntioxidantDefense System

In this study, the protective role of salicylic acid (SA) and trehalose (Tre) in relation to lipid peroxidation, membrane leakage, membrane stability index, antioxidant defense system as well as non-enzymatic antioxidants were investigated in drought stressed wheat Gemmieza-7 (drought sensitive cultivar) and Sahel-1 (drought tolerant cultivar) plants. Water stress reduced bio-membranes stability through inducing its lipid peroxidation resulting in an increment in membrane leakage with marked decrease in membrane stability index of flag leaf of both wheat cultivars during grain-filling. Moreover, it was obvious that drought significantly increased the activity of ascorbic acid oxidase (AAO), peroxidase (POD) and phenylalanine ammonia lyase (PAL) activities and induced non-significant reduction in polyphenol oxidase (PPO) activity in flag leaves of both wheat cultivars during grain-filling in comparing with well watered plants. Among cultivars, tolerant one showed higher enzymes activity than the sensitive one. Application of SA and/or Tre markedly increased AAO, POD and PAL activities and non-significant decrease in PPO activity in flag leaf of water stressed wheat plants. Generally, SA and Tre treatment appeared to be the most effective treatment in counteracting the negative effects of water stress and Sahel-1 appeared to induce better results than Gemmieza-7 and proved to be more tolerant. Drought stress caused significant increase in the amount of total phenols and flavonoids in flag leaf of both cultivars during grain-filling where the sensitive plants accumulated more total phenols and flavonoids contents than the tolerant one. Furthermore, water stress increased the non-photosynthetic pigment content of the two wheat cultivars particularly drought sensitive one during grain filling. These results suggest that the exogenous application of SA and/or Tre assisted the plants to become more tolerant to drought stress-induced oxidative damage by upregulating the membrane characteristics and enhancing their antioxidant defense system as well as non- enzymatic antioxidants.

Involvement of spermine and spermidine in the control of productivity and biochemical aspects of yielded grains of wheat plants irrigated with waste water

Abstract A pot experiment was conducted to evaluate the beneficial effect of grain presoaking in spermine (0.15 mM), spermidine (0.3 mM) and their interaction with waste water (25%, 50%, 100%) polluted with heavy metals on yield and biochemical aspects of yielded grains of wheat plants (Triticum aestivum L.) variety Sakha 94. Irrigation of wheat plants with waste water decreased significantly all yield components (100 kernel weight, grain yield/plant, straw yield/plant, mobilization and crop indices) and water use efficiency. On the other hand, polyamines appeared to ameliorate the harmful disordered of heavy metals of waste water on yield components as well as water use efficiency. The effect was more pronounced with Spm + Spd treatment. In the majority of cases, carbohydrates, protein, phosphorus, ions content and growth promoters in yielded grains were decreased in response to waste water stress in wheat plants, meanwhile, chloride, heavy metals content and abscisic acid level were increased in yielded grains of wheat plants. Application of spermine, spermidine or their interaction appeared to mitigate the deleterious effects of waste water on the above biochemical aspects of yielded grains of wheat plants. Protein banding pattern in yielded grains showed induction of proteins with molecular weights 73, 70, 24, 20 and 15 kDa in response to waste water application. Furthermore, spermidine treatment caused appearance of new proteins with molecular weights 73, 70, 57, 24, 23 and 17 kDa in yielded grains. Grain yield of wheat plants was negatively correlated with chloride, heavy metals and ABA.

Synergistic effect of phytohormones on pigment and fine structure of chloroplasts in flag leaf of wheat plants irrigated by seawater

Abstract Plant hormones play vital roles in the ability of plants to acclimatize to varying environments by mediating growth, development and nutrient allocation. The present investigation was undertaken to have some information about interactive effects of seawater salinity and some plant growth regulators (gibberellic acid, indole acetic acid or abscisic acid) on leaf area, pigment and chloroplast ultrastructure as well as saccharides and protein content of wheat flag leaf. In the majority of cases, seawater at 10 or 25% increased pigment content, particularly carotenoids. On the other hand seawater reduced leaf lamina area, Hill activity and sucrose as well as polysaccharides and protein. The interactive effect of seawater and growth regulators accelerated the production of Chl a, Chl b and carotenoids by increasing the values of these pigment. Furthermore, grain pretreatment with gibberellic acid, indole acetic acid or abscisic acid induced marked increase in leaf lamina area, Hill activity and sucrose as well as polysaccharides and protein. Irrigation of wheat plants by seawater at 10 or 25% caused dramatic changes in chloroplast ultrastructure of flag leaf. These changes include disorganized membrane system, disruption of bounding membrane, reduction in the size and number of starch grains and an increase in plastoglobuli. The presoaking of wheat grains in GA3, IAA or ABA resulted in an increase of plant tolerance against the adverse effect of seawater particularly at 10%. This resistance was estimated by the presence of normal chloroplast.

Shikimic and Salicylic Acids Induced Resistance in Faba Bean Plants against Chocolate Spot Disease

Surveys for faba bean chocolate spot disease covering 6 districts in Delta of Egypt were conducted. Out of these surveys, six isolates of the pathogen were obtained and purified using single spore technique. These isolates were identified as Botrytis fabae. All isolates were subjected to pathogenicity tests to determine the most aggressive one. All isolates appear to have the potency to cause chocolate spot disease, but the isolate from Sherbin was considered to be the most aggressive one and was selected for further studies. In vitro, the effect of provided phenolic compounds on inhibition of mycelia growth and the growth rate of B. fabae was investigated and arranged as follows: salicylic acid > Shikimic acid > shikimic acid+salicylic acid, as compared to control values. Furthermore, significant reduction in the disease incidence (%) and severity (%) were recorded in faba bean plants treated with salicylic acid followed by shikimic acid then their interaction. Botrytis fabae infection caused noticeable increase in the activity of defense enzymes (i.e., peroxidase, polyphenol oxidase and phenyl alanine ammonia lyase) in infected faba bean plants. In the majority of cases, the applied phenolic compounds induced additional increase in such enzymes than that sprayed with fungicide. This increment was concomitant with the increase in the endogenous total phenols, shikimic acid and salicylic acid content. In addition, the most effective treatment in enhancement faba bean resistance against B fabae infection was salicylic acid at 0.7 mM