Enhancement Of Hydrogel On Drought And Salt Resistance Of Populus Euphratica And P. Popularis

The effects of hydrogel on drought and salt resistance of a tolerant woody species, Populus euphratica Oliv. and a intolerant tree species, P.popularis were investigated under controlled conditions. The hydrogel used was Stocksorb 500 XL (crosslinked poly potassium-co-(acrylic resin polymer)-co-polyacrylamide hydrogel) that manufactured by Stockhausen GmbH Krefeld (Germany). Amendment of soil (dry weight) with 0.5% Stocksorb 500 XL enhanced drought and salt tolerance of the two tested poplar genotypes, but the effect of hydrogel was more pronounced in P.popularis, e.g. drought-treated and NaCl-treated P.popularis plants exhibited leaf wilting and necrosis after 18 days and 25 days of treatment, respectively, whereas the hydrogel amendment delayed the occurrence of drought- and salt-induced leaf injury by 12 days and 20 days. The experimental results and the main conclusions were the following:Compared with water stressed-plants, hydrogel-treatment evidently retarded the decomposition of chlorophylls(Chl) and proteins in leaves, but increased stomatal conductance (Cs), unit transpiration rate (TRN) and net photosynthetic rate (Pn) of the two genotypes.Furthermore the application of hydrogel reduced the content of active oxygen species(AOS) and malomdiadehyde(MDA), and decreased the membrane permeability in stressed P.popularis, accordingly the membrane integrality was remained during the period of water stress. As a result, the growth of droughted seedlings was less reduced compared with non-hydrogel-treated plants. The maintenance of plant water status by hydrogel is due to the super water-absorption capacity of Stocksorb 500 XL, which 1) lower the stomatal limitations on photosynthesis at the very beginning of drought stress, and 2) reduced non-stomatal limitations on CO2 assimilation in a longer-term and severe water stress. Consequently the drought resistance of plants was improved.Under saline conditions, hydrogel-treatment markedly limited the buildup of salt ions (Na+ and Cl-) in leaves of P. euphratica and P.popularis, but increased stomatal conductance (Cs), transpiration rate (TRN) and net photosynthetic rate (Pn) of the two genotypes.Moreover, the application of hydrogel assisted the salt-sensitive genotype P.popularis to maintain the activity of superoxide dismutase (SOD) and peroxidase (POD) isoenzymes, thus remaining the capacity to eliminate salt-induced reactive oxygen species (ROS) under salt stress. The reduction of salt uptake by hydrogel amendment was the...