A. M. Hamada

Counteraction of salinity stress on wheat plants by grain soaking in ascorbic acid, thiamin or sodium salicylate

The interactive effects of salinity stress (40, 80, 120 and 160 mM NaCl) and ascorbic acid (0.6 mM), thiamin (0.3 mM) or sodium salicylate (0.6 mM) were studied in wheat (Triticum aestivum L.). The contents of cellulose, lignin of either shoots or roots, pectin of root and soluble sugars of shoots were lowered with the rise of NaCl concentration. On the other hand, the contents of hemicellulose and soluble sugars of roots, starch and soluble proteins of shoots, proline of either shoots or roots, and amino acids of roots were raised. Also, increasing NaCl concentration in the culture media increased Na+ and Ca2+ accumulation and gradually lowered K+ and Mg2+ concentration in different organs of wheat plant. Grain soaking in ascorbic acid, thiamin or sodium salicylate could counteract the adverse effects of NaCl salinity on the seedlings of wheat plant by suppression of salt stress induced accumulation of proline.

Effect of NaCl salinity on growth, pigment and mineral element contents, and gas exchange of broad bean and pea plants

Increasing salinity of growth medium induced a reduction in growth and transpiration rate. The concentrations of chlorophylls and carotenoids were increased in most cases in broad bean leaves while in pea plants they remained more or less unchanged with the rise of salinization up to 80mM NaCl. Thereabove a significant decrease in these contents was observed. A stimulation of the net photosynthetic rate of pea was observed at the lowest levels of NaCl but at the highest levels inhibitory effect was recorded. In broad bean all salinization levels inhibited photosynthetic activity, but dark respiration of both plant species was stimulated. The content of Na+ in the roots and shoots of both species increased at increasing salinity. In broad bean, Ca2+ concentration in shoots and K+ and Ca2+ contents of roots increased at increasing salinization, while in pea plants, the content of K+ and Ca2+ was almost unaffected by salinity. Salinity induced an increase in the content of these ions in pea roots. Mg2+ content in shoots and roots of both broad bean and pea decreased at increasing salinity except in roots of pea, where it was generally increased.

Effects of Exogenously Added Ascorbic Acid, Thiamin or Aspirin on Photosynthesis and Some Related Activities of Drought-Stressed Wheat Plants

Water shortage induced numerous and complex effects on plant growth, photosynthesis and metabolism. However in some plants, the photosynthetic apparatus is remarkably resistant to dehydration (1;2), thus allowing a rapid recovery of the plant after rehydration.

Alteration in growth and some relevant metabolic processes of broad bean plants during extreme temperatures exposure

The effect of heat-shock (42 °C) or chilling-shock (5 °C) on growth and some relevant metabolic changes of broad bean (Vicia faba L.) were studied. Both heat and chilling-stress induced a reduction in growth rate, membrane stability and content of photosynthetic pigments (chlorophyll a, b and carotenoids). K+ efflux and UV absorbance increased at increasing or decreasing temperature. Considerable variations in the content of cell-wall components (pectin, cellulose, hemicellulose and lignin), cell-wall associated proteins, soluble sugars, starch, total lipids, glycolipids, phospholipids and sterols were induced by extreme temperure.

Alleviation of the adverse effects of NaCl on germination of maize grains by calcium

The lengths of roots and shoots, fresh and dry matter yield, and the contents of insoluble saccharides and free amino acids were reduced with the rise in NaCl concentration. However, under combination of NaCl with Ca2+ ions, these parameters generally raised. Contents of soluble saccharides, proline and quaternary ammonium compounds increased with increasing NaCl concentration, but under addition of CaCl2 or CaSO4, contents of these compounds were decreased. Low concentrations of NaCl stimulated soluble proteins, production, but higher concentrations decreased the content of soluble proteins. Addition of Ca2+ in the media did not improve the soluble protein production. Insoluble proteins content was increased with the rise of salinity level, but these effects were more pronounced with NaCl and CaCl2 or CaSO4 than with NaCl only.

Effect of NaCl, water stress or both on gas exchange and growth of wheat

Responses of wheat (Triticum aestivum L.) to various concentrations of NaCl and levels of drought were followed. With the rise of NaCl or drought, or NaCl and drought together, growth was retarded. The water content of shoots and roots was mostly unchanged. The chlorophyll and carotenoid contents were increased in plants subjected to salinity or drought or both. Only high salinity level induced a considerable decrease in net photosynthetic rate (PN) and dark respiration rate (RD). PN and RD were decreased with the decrease of soil moisture content. The content of Na+ in the shoots and roots of wheat plants increased with increasing salinity or decreasing soil moisture content or both treatments. Considerable variations in the content of K+, Ca2+ or Mg2+ were induced by the NaCl, drought or both treatments.

Thiamine treatments alleviate aphid infestations in barley and pea.

Treatment of plants with thiamine (Vitamin B1) has before been shown to activate plant defence against microorganisms. Here, we have studied the effects of thiamine treatments of plants on aphid reproduction and behaviour. The work was mainly carried out with bird cherry-oat aphid (Rhopalosiphum padi L.) on barley (Hordeum vulgare L.). Aphid population growth and aphid acceptance on plants grown from seeds soaked in a 150μM thiamine solution were reduced to ca. 60% of that on control plants. R. padi life span and the total number of offspring were reduced on barley plants treated with thiamine. Healthy aphids and aphids infected with the R. padi virus were similarly affected. Spraying or addition of thiamine at 150μM to nutrient solutions likewise resulted in reduced aphid population growth to ca. 60%, as did plant exposure to thiamine odour at 4mM. Thiamine treatments resulted in reduced aphid population growth also when tested with grain aphid (Sitobion avenae F.) on barley and pea aphid (Acyrthosiphon pisum H.) on pea (Pisum sativum L.). There was no direct effect of thiamine on aphid reproduction or thiamine odour on aphid behaviour, as evaluated using artificial diets and by olfactometer tests, respectively. Two gene sequences regulated by salicylic acid showed higher transcript abundance and one gene sequence regulated by methyl jasmonate showed lower transcript abundance in thiamine-treated plants but not in control plants after aphid infestation. These results suggest that the aphid antibiosis and antixenosis effects may be related to priming of defence, but more studies are needed to explain the effects against aphids.

Effects of salinity and heat-shock on wheat seedling growth and content of carbohydrates, proteins and amino acids

The effects of salinity (0, 50, 100, 150, and 200 mM NaCl) and heat-shock (42°C) and their interactions on germination, seedling growth, and some relevant metabolic changes of two cultivars (cv. Giza 155 and cv. Stork) of wheat (Triticum vulgaris L.) were studied. Germination studies indicate that plants tolerated salinity up to 100 mM NaCl. The lengths of roots and shoots and their water content, as well as fresh and dry matter yield of cv. Giza 155 seedlings remained more or less unchanged up to 100 mM NaCl and of cv. Stork up to 50 mM NaCl. Salinity induced progressive increase in soluble carbohydrates, soluble proteins and proline in cv. Giza 155 and in soluble proteins, proline and other free amino acids in cv. Stork. However, under the higher salinity levels, in cv. Giza 155 increase in soluble carbohydrates was accompanied by lose in other free amino acids, whereas in cv. Stork an opposite effect was obtained. Heat-shock treatment (42°C for 24 h) induced a significant decrease in the final germination percentage, the shoot and root lengths, fresh matter yield and the water content. The dry matter yield of the two cultivars was considerably increased as compared with the corresponding treatments with NaCl only. Heat-shock treatment resulted in a significant increase, in the amount of soluble carbohydrates and proline in salt treated seedlings of both cultivars. The pattern of changes in amino acids was opposite to that of soluble proteins, indicating that the increase in soluble proteins was at the expense of other amino acids in cv. Giza 155 andvice versa in cv. Stork.

Genotypic differences and alterations of protein patterns of tomato explants under copper stress

In vitro response of six tomato genotypes to different copper concentrations was studied. Cu was toxic to tomato explants at a relatively high concentration (100 µM), which reduced callus growth and shoot regeneration. Peto-86 followed by UC-97-3 were more tolerant to copper than the other genotypes. Cu (100 µM) induced the synthesis of eight new proteins (70.86 - 14.78 kD) in Peto-86 and six in Western Improve (46.43 - 14.78 kD) and UC-97-3 (77.69 - 14.78 kD). Cu-stress reduced the expression of some enzymatic bands of alcohol dehydrogenase and esterase, meanwhile, one peroxidase band at the locus Prx-1 was newly expressed under Cu-treatment.

Evaluation of Two Biologically Active Compounds for Control of Wheat Root Rot and its Causal Pathogens

Abstract The main aim of this study is to evaluate the efficiency of two biologically active compounds (Strom and F-760) in control of wheat root rot disease and its causal organisms. Fusarium graminearum, F oxysporum, F solani and Bipolaris sorokiniana were used as target organisms. In vitro, the two compounds showed fungicidal effect on all investigated pathogens resulted in suppression of radial growth and mycelial dry weight of them. Under greenhouse conditions, treatment of wheat grains with either Strom or F-760 before cultivation significantly reduced the percent of disease distribution as well as the mean disease rating of plants in both seedling and flowering stages. Fresh and dry weights of plants as well as water maintenance capacity were increased as the result of applying these compounds as seed dressing. Also data showed that the membrane stability of plants was injured as a result of infection with all investigated organisms, while this injury was alleviated when F-760 and Strom were applied. The K+ efflux and the leakage of UV-absorbing metabolites was stimulated with fungal infection. However, F-760 and Storm treatment partially retarded the stimulatory effect on leakage of K+ and UV-absorbing metabolites of fungal infected plants. On the other side, the fungal infection had inhibitory effects on pigment fractions (chlorophyll a, b, and carotenoids) biosynthesis in wheat leaves. This retarding effect was partially or completely alleviated as the grains were treated with the applied compounds.