Drought has become an important challenge in crop cultivation, so detection of drought-tolerant cultivars by screening existing genotypes is a valuable tool in the effort to attain food security worldwide. The drought stress tolerance of two wheat cultivars was determined through treatments with PEG (−0.4 MPa) and SA (0.5 mM). The resulting data on seed germination and seedling growth indicated that Misr-2 cultivar is more drought-tolerant than Gemaza-12. Under non-stress conditions, Misr-2 had higher pigment values, higher levels of soluble sugars (Glu, Fru, and Suc) and antioxidant enzyme activity (CAT, APX, POX and SOD), but lower proline values than those in Gemaza-12. Gemmaza-12 had higher expression of proline synthesizing gene (P5CS) but lower expression of proline-degrading genes (ProDH and P5CDH) than Misr-2. Under drought conditions, Gemaza-12 needed more osmoregulators and antioxidants than Misr-2 to minimize the negative effects of drought and associated oxidative stresses. Soluble sugars, proline content and antioxidation enzymes were higher in Gemaza-12 than in Misr-2. Under drought stress, stimulation of P5CS and retardation of ProDH and P5CDH were higher in Gemaza-12 than in Misr-2. Although treatment of stressed plants with SA stimulated P5CS gene in both cultivars, retardation of ProDH and P5CDH was more pronounced in Gemaza-12 than in Misr-2. Consequently, we conclude that seed germination and seedling growth could be used to compare drought tolerance of wheat cultivars and seed soaking in SA improves drought tolerance. Our results confirmed that an increase in proline production is one of the symptoms of drought stress in plants.

SUBCULTURE repeats was essential prerequisite for mass micropropagation in stevia but it accompanied by vitrification of the cultured shoots. Increase the number of shoots/explant without vitrification was detected when nodal segments of in vitro obtained shoots were subcultured twice, three weeks each, on Murashige and Skoog (MS) medium with 0.25mg/L BAP. From the third subculture, shoot multiplication decreased and vitrification increased as the number of subcultures increased; where 40% of the formed shoots of 10th subculture were vitrified. Decrease of water potential by polyethylene glycol (PEG) increased the incidence of shoot vitrification but shortened the period of subculture from three to two weeks delayed its appearance up to sixth subcultures. Also, application of anti-ethylene agents [AgNO3, CoCl2 or salicylic acid (SA)] decreased vitrification problems up to six subcultures. The best results were obtained by 1.7mg/L AgNO3 where verification was reduced without significant reduction in the number of shoots/explant and shoot growth. The equivalent concentration of AgNO3 in nano-particles form (AgNPs) showed a drastic increase in shoot vitrification (20%). When shoots of the 1st, 4th, 7th and 10th subcultures were subjected to genome amplification using RAPD or ISSR primers, the registered polymorphism under the influence of 1.7mg/L AgNO3 was lower than that of 1.7mg/L AgNPs; both of them were lower than that of shoots cultured on anti-ethylene free medium (control).

IN VITRO grown potato cultivars shoots were used to understand….. how polyvinyl pyrrolidone (PVP) and three levels of potassiuminteract with two levels of salinity to determine Na+ and K+ contents,and antioxidant enzyme activities leading to control survival,multiplication and growth of cultured plant shoots. Explant survivaland the number of regenerants/explant decreased with the increase of NaClconcentration but increased K+ content of the culture medium from 20mM to 30 mM improved explants survival frequency and the growthparameters estimated under relatively high salt stress (80 mM NaCl) inboth cultivars. Also, number of regenerants was influenced by K+ levelwhere it was higher in medium containing 40 mM NaCl and 30 mMK+ than other cultured on the same NaCl concentration with 20 mMK+. The positive effect of 30 mM K+ on the previous parameters wasassociated with increase shoot K+ content leading to decrease Na+/K+ratio and increase of some antioxidant enzymes (SOD, POX and CATin Agria or SOD, POX and APX in Hermes) activity, especially underrelatively high salt stress. PVP application increased K+ content andactivities of some antioxidant enzymes (CAT and APX) but decreasedNa+/K+ ratio of shoots subjected to relatively high salt stress in Agriabut under both salt stresses in Hermes. Consequently, sufficientpotassium supply was necessary to conserve low Na+/K+ ratio andefficient scavenging system by antioxidant agent (PVP) application orincrease the endogenous antioxidant enzymes activities leading tominimize the negative effect of salt stress on in vitro grown potato.

The aim of this work was to study the response of two wheat cultivars with different drought tolerance to PEG (-0.4 Mpa) and SA (0.5 mM). Data of seed germination and seedling growth indicated that Misr-2 cultivar was more drought tolerant than Gemmeiza-12. Under non- stress conditions, Misr-2 had higher values of pigments, soluble sugars (Glu, Fru and Suc) and activities of antioxidant enzymes (CAT, APOX, GPOX and SOD) but lower values of proline than those of Gemmeiza-12. The cultivar with a higher proline content (Gemmeiza-12) compared to the other cultivar had a higher expression of proline synthesizing gene (P5CS) but lower expression of proline degrading genes (PDH and P5CDH). Under drought conditions, the drought-sensitive (Gemmeiza-12) needed more osmoregulators and antioxidants than drought-tolerant cultivar (Misr-2) to minimize the negative effects of water and associated oxidative stresses. Therefore, soluble sugars, proline content and anti-oxidation enzymes were higher in Gemmeiza-12 than Misr-2. Also, under drought stress, up-regulation of P5CS and down-regulation of PDH and P5CDH in Gemmeiza-12 were higher than Misr-2. While treatment of the stressed plants with SA up-regulated P5CS gene in both cultivars, down-regulation of PDH and P5CDH in Gemmeiza-12 was clearer than Misr-2.

The effect of salinity, drought and salicylic acid on growth and esterase expression of peanut plants were studied. Seeds of peanut were able to germinate even under relatively high concentration of NaCl (157.5 mM) or PEG (25%). In general, seedling growth was less tolerant to salt stress than vegetative growth stage of peanut plants grown in hydroponic culture containing NaCl, vice versa was detected when PEG was used.While the application of 0.1 mM salicylic acid (SA), inhibit peanut seed germination, it improved seedling and vegetative growth parameters under moderate concentration of NaCl (105 mM). Seedling and vegetative growth parameters were significantly reduced by increase the concentrations of PEG. Application of SA improved growth parameters of peanut plants subjected to 10% PEG.In hydroponic culture, peanut was more sensitive to PEG than NaCl where plants wilted in three days under relatively high PEG concentrations. Root of peanut seedlings increased the esterase expression under the influence of moderate salinity (105 mM) and drought (10% PEG) stresses through increase the number and staining intensity of isoenzyme forms.Increase the number of isoenzyme forms and/or staining intensity as an indicator of increased activity of the enzyme was detected when peanut plants were hydroponically grown in solution with relatively high NaCl or PEG. Application of SA increased the number and/or the staining intensity of isoenzyme forms during seedling or vegetative growth in hydroponic culture containing relatively high concentration of NaCl or PEG.