Tamarix nilotica is a perennial halophyte growing naturally at the Mediterranean coastal salt marshes. Vegetative parts were collected in two successive winters and summers to investigate the seasonal effects on the ecomorphological and physiological responses of T. nilotica. The results indicated that either in winter or summer seasons, T. nilotica can reduce the effect of soil salinity by excreting salts outside its body through salt glands. Summer season was characterized by low content of soil moisture (due to rare rainfall), high soil EC, high light intensity and high temperature; there-fore, plant induced certain morphoanatomical changes in leaves and stem to face the previously mentioned adverse conditions. The most remarkable changes to reduce transpiration process was found by decreasing leaf area and increasing cuticle thickness and mesophyll tissue thickness. In addition, the most marked physiological changes in summer were the significant in-crease in total phenols, proline, free amino acids and total soluble sugars. These compounds can work as osmotic regulators and/or antioxidants. These features enhance the defensive mechanism against dehydration and permit T. nilotica to tolerate the stress conditions in salt marsh habitat.

Drought has become major environmental constraint to the crops productivity and the sustainability of agriculture. Recently, using biochar (BC) as a soil conditioner has aroused much interest and proved to be an effective tool for improving soil properties and crops growth and yield. Therefore, a pot trial was conducted using wheat plant (Triticum aestivum L.) with three water regimes (60, 30 and 15% of water holding capacity(WHC)) and three rates of biochar (0, 2%, and 5%) to investigate the impact of biochar on growth and yield components. The results showed that WHC enhanced in the presence of BC leading to improving the availability of water to wheat plants grown in BC-treated soil. Plants grown in BC-amended soil had higher growth and plant biomass, net assimilation rates than those in un-amended soil. Biochar addition positively affected wheat growth parameters including increases in leaf area, number of leaves per plant, tillers number per plant, height of plant as well as shoot to root fresh weight ratio. Particularly interesting is the improvements in yield attributes. These results led us to conclude that the application of black carbon would enhance the growth and yield of crops under insufficient water supply. On other hand, biochar can be considered an effective tool for sustainable agriculture and hence mitigating the injurious effects of drought conditions on plants.

In total, 50 Rhizobium isolates were isolated from the mature root nodules of common beans plants (Phaseolus vulgaris) grown in different nine governorates of Egypt. PHB was optimized by the identified strain using response surface methodology. A total of 11 parameters (pH, incubation period, inoculum size, temperature, agitation speed, mannitol, sucrose, yeast extract, glycine, K2HPO4, and MgSO4) were analyzed for their significant effects on PHB production by the Plackett–Burman design (PBD). Sucrose, yeast extract, glycine, and MgSO4 were the main significant factors affecting PHB accumulation. Central composite design (CCD) of the response surface methodology was used to determine the optimum levels of the selected factors. Rhizobium phaseoli reached the maximum production (4.997 g/L) at run 36 in the presence of 25 g/L of sucrose, 0.0 g/L of yeast extract, 0.87 g/L of glycine, 0.3 g/L of MgSO4, and 5% of inoculation size. In vitro experiments were carried out to test the effect of different stress conditions (pH: 6–11, temperature: 5°C–50°C, salinity: 0.01%–7%, and drought: 0%–5% w/v) on the growth of Rhizobium phaseoli. The results showed that Rhizobium phaseoli can withstand 3% –5% NaCl, high temperature of 30°C– 45°C, alkalinity at pH value of 8 – 10, and drought stress at 3% – 5% w/v polyethylene glycol with growth loss of 50% when grown on modified medium and 75% when grown on the basal one. In vivo experiments were done to study the effect of drought stress levels on the growth parameters of common bean plants. In general, all the treatments with Rhizobium phaseoli grown on the modified medium were superior to Rhizobium phaseoli grown on the basal medium. Also, they showed high tolerance of drought conditions.

An experimental field trial was conducted in seasons of 2015 and 2016 at Giza Experimental Station of Agricultural Research Centre (ARC), Egypt to evaluate the foliar spray effect with transpiration regulators (Potassium, Kaolin and Ascorbic acid) and three levels of irrigations (100%, 80% and 60% of Et0) on yield, its attributes, and water productivity of two sunflower cultivars (Giza 102 and Solala 120). The factorial treatments were arranged in split- split plot design with three replications. The irrigation levels (100%, 80% and 60% of Et0) were devoted for main plots, while subplots contained the three spraying treatments of transpiration regulators. (Potassium at 1%, Kaolin at 3% and Ascorbic acid at 100 ppm), in addition to control treatment (water spray). Sub-sub plots were occupied by the two sunflower cultivars (Giza 102 and Solala 120). Obtained results proved that, increasing irrigation levels up to (80- 100%) caused significant increase in all growth characteristics, photosynthetic pigments (total chlorophyll), relative water content (RWC %) and seed oil %. Also, yield parameters being head diameter, 1000-seed weight and seed yield) show significant reduction under water deficit. Foliar spray with (Potassium at 1%, Kaolin at 3% and Ascorbic acid at 100 ppm), positively affected all the growth and physiological criteria of the tested plants compared with control. Generally, under low irrigation levels, application of transpiration regulators effectively reduced the detrimental impact of drought stress on growth, yield and its components of the two used cultivars in the two seasons. While, foliar spraying of potassium under 100% of Et0 gave the best treatment in this respect. Concerning cultivars, WUE (water use efficiency) for Solala 120 was significantly higher than for Giza 102 in the two seasons. All interactions among factors under study due to WUE were not significant in 2015 and 2016 seasons.

Two pot experiments were conducted on the 17th and 11th of march during 2015 and 2016 growth seasons respectively at the greenhouse, Dept. Agric. Botany, Faculty of Agriculture, Ain Shams University, Shoubra El-Kheima, Egypt to investigate the impact of drought stress on some growth, biochemical and anatomical parameters of Thymus vulgaris L. Plants were exposed to two different irrigation levels: 70-80% and 30-40% of water holding capacity (WHC) as well-irrigated and drought stressed plants respectively. The results indicated that all investigated growth parameters and leaf photosynthetic pigments were decreased significantly by exposing to drought stress. There were significant increase in the concentration of reactive oxygen species (ROS) as indicated by measuring of H2O2 and malondialdehyde (MDA). A similar trend was observed in respect to osmolytes including proline, total soluble sugars and free amino acids. Also, drought stress increased significantly total soluble phenols and the specific activity of Phenylalanine ammonia-lyase (PAL) and Polyphenol oxidase (PPO), whereas, no significant differences were detected in peroxidase (POD). The anatomical examination showed that there were several significant changes associated with water limited supply in the stem and leaf of plants.