Evaluation of water deficit stress on physiological and anatomical some aspects of alfalfa (Medicago sativa L,) cultivars.

A field experiment was conducted during 2005 – 2006 in Agriculture Research centre of Jiroft and Kahnouj to determine the effect of water stress on some physiological and anatomical aspects of alfalfa cultivars. Using a split plot design based on randomized Complete block Design (RCBD) with three replications. The three levels of water stress 1)- severely stressed (irrigation when soil moisture reached to %25 of F. C)، 2)- moderately stressed (irrigation when soil moisture reached to %50 of F. C) and 3)- least stressed (irrigation when soil moisture reached to %75 of F. C) was the main plot factor and five cultivars of alfalfa (1- Yazdi، 2- Nikshahri، 3- Rangar، 4- Bami and 5- Baghdadi) were collected sub plots. Several drought stress indicators، including leaf relative water content (RWC)، cell membrane stability expressed as electrolyte leakage، number of stomata and length of the stomatal aperture characteristics of leaves were examined. The results showed that water deficit stress، significantly reduced relative water content (RWC) values from 86% to 69%. With increasing water deficit stress، electrolyte leakage were increased in alfalfa cultivars the tolerant cultivars to drought (Nikshahri and Bami) maintained higher RWC at severe water stress treatment. The number of stomata and length of the stomatal aperture decreased with increasing water stress level. As overall result is to conclud that، stomata number of alfalfa cultivars tolerant to drought is less and RWC Ratio higher in low water stress condition compared to sensitive cultivars.