عنوان مقاله [English]
نویسندگان [English]چکیده [English]
An investigation of chlorophyll quick fluorsence variations was made in the Reaserch Field of Islamic Azad University- Karaj in 2007. The experimental design was a split plot one in form of a complete randomized block design with 4 replications. Drought stress was cosiderded in three levels of 40%, 60%, and 75%, on the basis of depletion of soil moisture as the main factor and the factor of microelements in three levels of 0, 3, 5 lit/ha. The evaluated traits were chlorophyll fluorsence parameters, RWC, chlorophyll content and cell memberane stability, as well as grain yield in two stages. Results, indicated that the stress effects on F0, chla, chlab and GY and also FV/FM, and chlb were significant at the first stage, while in the second stage they were significant on F0 (p<0.05), and while in other parameters they were non significant. The triat means of FV/FM, chlab, chlb, chla andcell memberan stability declined while F0 increased as drought stress levels increased (at the first stage), but at the second stage F0 increased although Fv decreased. At the first experimental time microelements' effects were significant on F0 (p<0.05) and EC (P<0.01) while at the second stage, they were significant on F0 (p<0.05). The means indicated that F0 increased in each stage, but cell membrane stability decreased although microelement levels increased. FV/FM, chlab, chla and EC had the highest while F0 the lowest correlation coefficient with grain yield. At the second stage the highest correlation coefficient was observed with FV/FM, FV, FM and the lowest with F0 with GY. Interaction effects were significant on EC (p<0.01) at the first and on F0 (p<0.05) at the second experimental time. Result showed that, masured parameters under drought stress can act as an index for determination of intensity of stress. Also FV/FM, FV, and even Fm are suitable for an investigation of intensity stress.