The study was aimed to investigate the ability of two date palm genotypes (Shamia and Amri) to tolerate drought stress throughout their micropropagation period. Some morpho-physiological basis of drought responses in the regenerated seedlings were evaluated. This may help in selecting drought stress tolerance and detecting other quantitative traits. Direct organogenesis technique, using shoot tip explants and supplementation of mannitol to the MS basal media has been chosen to tackle this issue. The data indicated that emberyogenesis obtained in the two genotypes followed normal development and had ability to competent to regeneration and converted into plantlets under drought stress conditions. However, swelling, numbers of embryos and shoots/jar, plantlet height and root length were decreased. All these parameters recorded higher values in Shamia genotype than those of Amri. Photosynthetic rate, transpiration rate and stomatal conductance of the regenerated plants in both date palm genotypes, were decreased whereas water use efficiency was increased with an increase in water stress level. Shamia genotype obtained higher values than Amri genotype in this respect. Carbon isotope discrimination was higher (more negative values) in shoots than in the roots and decreased with decreasing water supply. The values of maximum (Fm) and variable (Fv) fluorescence of the chlorophyll showed a significant reducing trend in both genotypes under stressed condition. The quantum yield of photochemistry (Fv/Fm) was also decreased. The mean Fv values as well as Fv/Fm ratio of both date palm genotypes in water stressed plants were significantly lower than those in the control. It could be concluded that both date palm genotypes studied, with the superiority of Shamia, have an ability to tolerate water stress under in vitro system. Chlorophyll fluorescence can be used as a tool, with other examined useful physiological characters, to screening date palm genotypes for drought resistant.
M.N.M. Helaly and A.M. Hanan El-Hosieny, 2011. In vitro Selection and Photosynthetic Characterization of Date Palm Regenerated Seedling as Affected by Water Stress. American Journal of Plant Physiology, 6: 126-143.