The experiment was conducted through two successive seasons of 2008 and 2009 at ElBosaily farm, EI-Behira governorate at the North Coastal of the Nile Delta, in Egypt. This work aimed to study the effect of three green-house covers (polyethylene sheet, white and black net) and three irrigation levels [80%, 100% and 120% of the potential evapotranspiration estimated according to class A pan equation (ET,)], applied by drip irrigation system, on plant growth and crop yield of Cucumber (Cucumis sativus L.. cv. Reda F1). The experimental design was split- plot with three replicates. The results showed that white net green-house cover optimized growth and yield of cucumber plant. White net cover treatment recorded the highest vegetative growth (plant height, number of leaves, total leaves area, total fresh and dry weights), and significantly increased total yield. The highest vegetative growth was obtained by 100% ET, compared to 80 and 120% ETo treatments. The interaction among water treatment and green-house cover indicated the highest vegetative growth and crop yield were obtained under white net cover wi1th 100% ET0,.

A greenhouse pot experiment was carried out to investigate the effect of salinity and potassium at different levels alone or in various combinations on growth, mineral and proline content in leaves of plantlets of Phoenix dactylifera L. cv. Bartomouda (in vitro production, two years old from acclima tized them). The following treatments were applied: three levels of salinity Na Cl + Ca C12 w.w 2:1 (14000, 16000 and 18000 ppm.) and two levels of potassium (2000 and 3000 ppm) in addition to control (no salts or potassium used), salts and potas sium were added in the irrigation water. In general, all levels of salinity significantly decreased various growth parameters such as plant height, number of leaves and roots, root length, fresh and dry weights of leaves than that of the control. These parameters were decreased with increasing salinity levels, whereas it, significantly increased Na, Ca and K contents in leaves with high content of proline. The treatment 18000 ppm salts gave the highest significant reduction of the growth parameters, while caused an increase in proline Na, Ca, and K contents compared to control treatment (no salts) . This was true in both seasons. The applications of potassium significantly increased the previous growth parameters as compared with the control treatment (without salts and potassium) the treatment 3000 ppm had the highest results. Moreover the applications of potassium gave high alleviated the negative effects of salt stress, the treatment 3000 ppm gave the best results on the growth parameters of date palm plantlets grown under salinity condition . Regarding the interaction the obtained data revealed that the interaction between treatment 3000 ppm potassium and 14000 salts produced the highest significant results. Gen erally, from the obtained results it can conclude that the plantlets of date palm produced by tissue culture can be tolerated salt stress by addition of potassium which can significantly ameliorate the harmful effects of salts, positive effects on the growth parameters of the plantlets was showed by potassium applications.