Effect of drought stress by polyethylene glycol on morphological, physiological and biochemical characteristics on selected cultivars almond

This study during the year of 2011 and 2012 in horticultural research station and seed and plant improvement Institute, Karaj as factorial on the base completely randomized design was done. Factors include almond seedlings tested in 6 levels (supernova, Perlis, D 124, Marcona, Rabie, and k1-16) and osmotic stress of polyethylene glycol in 5 levels (0, 2-, 4-, -6 and 8-bar). The results showed that with drought stress on plants, plant height, number of leaves, the amount of chlorophyll a, chlorophyll b and total chlorophyll, the amount of glucose and fructose content, relative humidity content decreased and the amount of proline and the rate of ion leakage increased, but increase or reduce these traits in the cultivars with each other had significant differences. The results of investigation growth traits showed that Peerless and k66 cultivars had the most sensitivity to the drought so that the number of these plants leaves and their height under osmotic stress -2 bar are reduced in comparative with plant control significantly. The most resistance to drought was shown in D-124 and Marcona cultivars so that osmotic stress could endure up to -6 bars and only in osmotic stress -8 bars, the number of leaves and their height was significantly reduced compared with control plants. The results from physiological and biochemical characteristics were very similar with the results of the measurements on morphological traits. D-124 and Marcona cultivars had the highest level of production proline and the lowest ion leakage. They were diagnosed as the most resistance to drought stress, while cultivar k16 had the most sensitive to drought stress.