Middle-East Journal of Scientific Research 13 (8): 998-1009, 2013 ISSN 1990-9233 © IDOSI Publications, 2013 DOI: 10.5829/idosi.mejsr.2013.13.8.3531 Corresponding Author: Mostafa Ahmadizadeh, Young Researchers Club, Jiroft Branch, Islamic Azad University, Jiroft, Iran. Cell: +989194457655. 998 Physiological and Agro-Morphological Response to Drought Stress Mostafa Ahmadizadeh Young Researchers Club, Jiroft Branch, Islamic Azad University, Jiroft, Iran Abstract: Although, drought stress has been well documented as an effective parameter in decreasing crop production; developing and releasing new varieties which are adaptable to water deficit conditions can be a constructive program to overcome unsuitable environmental conditions. A good understanding of factors limiting yield now provides us with an opportunity to identify and then select for physiological traits, which increase drought tolerance and yield under rainfed conditions. Applying different physiological and agro-morphological tests to appreciate drought tolerance in plant leads to faster selection methods. Therefore, these characters can be used as an indirect selection criterion for screening drought tolerance plant materials, this strategy will lead to new cultivars with high yield potential and high yield stability that in turn will result in superior performance in dry environments. Key words: Morphological traits Chlorophyll fluorescence Oxidative stress Germination Electrolyte leakage INTRODUCTION genetic behavior and type of gene action controlling Drought is raising threat of world. Most of the appropriate breeding procedure for the purpose of genetic countries of the world are facing the problem of drought. improvement. Hence, the success of any selection or The insufficiency of water is the principle environmental hybridization breeding program for developing drought- stress and to enter heavy damage in many part of the tolerant varieties depends on precise estimates of genetic world for agricultural products [1-5]. Among the variation components for traits [20, 21]. It inhibits the environmental stresses, drought stress is one of the most photosynthesis of plants, causes changes in chlorophyll adverse factors for plant growth and productivity [6, 7]. contents and components and damage to the Drought stress can reduce grain yield, have estimated the photosynthetic apparatus [22]. In addition, it inhibits the average yield loss of 17 to 70% in grain yield due to photochemical activities and decreases the activities of drought stress [8]. Drought is a complex physical- enzymes in the Calvin Cycle in photosynthesis [17]. chemical process, in which many biological macro Conventional plant breeding attempts have changed over molecules and small molecules are involved, such as to use physiological selection criteria since they are time nucleic acids, proteins, carbohydrates, lipids, hormones, consuming and rely on present genetic variability. ions, free radicals, mineral elements [9-14]. The ability of Tolerance to abiotic stresses is very complex, due to the a cultivar to produce high yield over a wide range of intricate of interactions between stress factors and environmental condition is very important. Response of various molecular, biochemical and physiological plants to water stress depends on several factors, such as phenomena affecting plant growth and development developmental stage, intensity and duration of stress and [16, 23]. cultivar genetics [15, 4]. The plant response is complex Morphological and agronomic traits have a special because it reflects over space and time the integration of role to determine the importance of each trait on stress effects and responses at all underlying levels of increasing yield, as well as to use those traits at the organization [16]. Improving drought resistance is, breeding programs, which at least lead to improving yield therefore, a major objective in plant breeding programs for and introducing commercial varieties under end seasonal rainfed agriculture in these regions [17-19]. Knowledge of drought stress condition [24]. Morphological characters target traits is a basic principle for designing an