Plant Archives Volume 20 No. 2, 2020 pp. 7795-7805 e-ISSN:2581-6063 (online), ISSN:0972-5210 MITIGATION OF WATER STRESS IN TWO PURSLANE (PORTULACA OLERACEA L.) CULTIVARS USING NANO SILICON AND FOLIC ACID Azza, M. Salama 1 , A.E. Ghoniem 2 and Abdel Wahab M. Mahmoud 3 1,2 Agricultural Botany Department, Fac. of Agric., Cairo Univ., Giza, Egypt. 3 Cairo University, Faculty of Agriculture, Plant Physiology Department, Giza, Egypt. Abstract A field experiment was carried out at Faculty of Agriculture, Cairo University, Giza, Egypt, during the two successive seasons of 2018 and 2019 to study the effect of foliar spray with nano silicon or folic acid and their combination on morphological, anatomical and chemical characters of two Purslane (Portulaca oleracea L.) cultivars (Egyptian and Turkey) under three water levels (100, 50 and 30% of field capacity). The results showed that spraying two cultivars with mixture of nano silicon and folic acid at 30% field capacity exhibited significant promotive effects on morphological and chemical characters compared with untreated plants. Concerning anatomical structure of leaf, treatment with a mixture nano silicon and folic acid at 30% of field capacity increase the thickness of both mid vein and lamina due to the increase in thickness of mesophyll tissue as well as in the dimension of the main mid vein bundle. Likewise, such treatment increased stem diameter of cortex, phloem and xylem tissues and decrease parenchymatous area of the pith compared with control. Spraying plants with mentioned mixture treatment at 30% field capacity increased almost all macro and microelements, besides carbohydrate, phenolic and ascorbic acid. Moreover, mixture treatment revealed significant effects of photosynthetic rate, stomatal conductive and water use efficiency compared with control. Key word: anatomy , Purslane, folic acid, nano silicon, chemical composition. Introduction Herbs today are typical well-being as opposed to the synthetics that need help considered equally dangerous to the further earth of mankind. However, the visually impaired dependence on synthetics can be in and kin returns with confidence for safety and safety from the natives (Hao et al., 2015). The assumption for this use will be that these crops are known as dynamic components (active principles or biologically active principles) that affect physiological (metabolic) processes of living organisms, including people. Mostly incredible numbers of contemporary drugs were also separated from prevalent plant species due to their use of conventional medicine (Graul et al., 2008). Wild crops are not generally eaten daily, but for humans they are a significant source of nutrients. It is known to have elevated concentrations of fatty acids (including -3 and -6), which are vital elements of human health. Purslane olecracea plant is an outstanding source of vitamin E, vitamin C, beta-carotene and glutathione- like antioxidants. Purslane is a wealthy source of isoleucine amino acids, Lucien, lysine, cysteine, phenylalanine, tyrosine, threonine and valine (Marcela et al., 2013). Portulaca oleracea is a very important plant because of its specific and ascribed all therapeutic characteristics to the presence of many biologically active compounds, flavonoids and medical functions (myricetin, quercetin, kaempferol, luteolin, apigenin, genistin and genistein), alkaloids, anthraquinone glycoside, respiratory glycoside and elevated content of -3 fatty acids (simopoulos, 2004). Drought stress is considered as one of the variables restricting crop efficiency a threat to crop success. Drought tolerance is an significant yield-related feature. In terms of plant physiology, dryness creates pressure in plant growth, yielding a 50-30 percent decrease in drought stress owing to low humidity in plant growth resulting from elevated evapotranspiration, elevated sunlight temperature (Ghodsi et al., 1998). In reality, with growing drought stress, the cell wall is wizened and loose, cell volume reduces, pressure reduces and the cell’s development potential is lowered based on the potential