| Abstract:
The research was conducted based on genetic variation of a black saxaul (Haloxylon aphyllum) plant population to find possible differences between the genotypes of the population, confronting various levels of water stress. A great number of progenies of four genotypes of the species were studied under four levels of water stress, field capacity, 20, 50, and 80% of available water by the plant, using a factorial statistical model based on randomized complete block design. Branch number and length, mainstem and crown diameter, leaf chlorophyll content and leaf osmotic potential were recorded during and at the end of growing season. Studies on genotype and water stress factors revealed, although there were significant differences between the genotypes based on the studied characters, water stress levels were not significantly different based on the short duration of the research. Species such as Haloxylon, which is not fast growing species, would not respond to the stress levels during a short period of time. The genotypes were significantly different based on leaf chlorophyll content. Correlation coefficients between the morphologic characteristics were also noticeable. Negative significant correlation between leaf chlorophyll with branch number and trunk diameter implied that desert plant species such as the species under study would take advantage of light color of less chlorophyll content to cope with high temperature and sun light of their habitats.
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