oa Impact of periodic drought stress on photosynthesis changes in Haloxylon aphyllum

Impact of periodic drought stress on photosynthesis changes was examined in branchlets of Haloxylon aphyllum. Parameters F0, Fm, Fv, and the amounts of chlorophyll a and chlorophyll b were the traits that were measured in this experiment. Drought stress factor was considered as lack of irrigation of potted-seedlings of two haloxylon species in periods 0, 2, 4, 6... 26 and 28 days, and each drought period were repeated 6 times. Analysis of variance showed that drought stress had significant impact on the parameters F0, Fm, Fv, Fv/Fm and t1/2 with 99% probability in the haloxylon. Drought stress intensity was significantly effective on the amount of both chlorophyll a and b and total chlorophyll at 99% level in Haloxylon aphyllum. Drought stress was extremely affected on values of chlorophyll a and b, and reduced them up to more than 50% compared to the control. The obtained data were reviewed within the format of a Randomized Complete Design. Analysis of data was made by using two-side variance analysis; and comparison of averages was made by using Duncan's test. Key words: Haloxylon, photosynthesis, stress, drought, fluorescence