All living organisms are subjected to changing in conservational conditions, to which they must adapt to. Stress is defined as a threat refers to the physiological balance of systems critical to survival organisms. Five yeast strains (Saccharomyces cerevisiae) were subjected to different adverse environmental situations, such as thermal, osmotic and oxidative (salt) stresses. The objective of this work was to detect the most tolerant yeast strains under salt or heat stresses.  Five yeast strains were exposed in a first experiment to heat stress at 20°C or 40°C beside to the control at 30°C to detect the more tolerant strain. The same yeast strains were subjected in a second experiment to two different concentrations of salt stress (NaCl); 0.5 or 1.0 M, separately, for two days (at 30°C as normal temperature for growth), other strains were exposed to 0.5 M concentration of NaCl for 24 hours, then 1 M for another 24 hours. For the heat stress results, strain S4 was more tolerant at 40oCwith insignificant difference compared to the control (30oC), while it showed significant difference at 20°C. Strain S5 also was more tolerant at 20oC with insignificant difference compared to the control. For salt treatment, the only insignificant value was for strain S3at 0.5M NaCl compared with the control.

Two experiments were carried out under low polyethylene tunnels which furnished with drip irrigation during the two successive winter seasons of 2014-2015 and 2015-2016 at Elbrollous area which represents the circumstance and conditions of coastal zone of north Nile Delta kafr Elsheikh Governorate. The objective of the investigation was to find out the effect of grafting by different cucurbita rootstocks on cucumber hybrid "ESHRAK" (Cucumis sativus, L.) on vegetative growth, flowering, yield and fruit characteristics, beside nutrient contents of cucumber plants. Results showed that grafted cucumber plants on Super Shintoza led to significant increase in vegetative growth,i.e., stem length, number of leaves, number of branches and leaf area,fruit fresh weight (g), number of fruits, total yield were greater with grafted cucumber plants on Super Shintoza followed by grafted cucumber plants on cv. Ferro. However grafting had no significant effect on potassium % of fruit on both seasons. The highest total yield was obtained by grafting cucumber plants on Super Shintoza rootstock followed by grafting on cv. Ferro rootstock by 130 % and 73 %, respectively in the first season and 160% and 147 %, in the second season respectively as compared with ungrafted cucumber plants. Accordingly, this study ensured that the use of rootstocks were more beneficial than ungrafted cucumber in both tested seasons.