R. Daneshvar rad - Department of Agronomy and Horticultural Science, Faculty of Agriculture science and Food Industries, Science and Research Branch, Islamic University, Tehran, Iran
H. Heidari Sharifabad - Department of Agronomy and Horticultural Science, Faculty of Agriculture science and Food Industries, Science and Research Branch, Islamic University, Tehran, Iran
M. Torabi - Horticulture Crops Research Department, Isfahan Agriculture and Natural Resource Research and Education Center, AREEO, Isfahan, Iran
R. Azizinejad - Department of Agronomy and Horticultural Science, Faculty of Agriculture science and Food Industries, Science and Research Branch, Islamic University, Tehran, Iran
H.R. Salemi - Agriculture Engineering Research Department, Isfahan Agriculture and Natural Resource Research and Education Center, AREEO, Isfahan, Iran
M. Heidari Soltanabadi - Agriculture Engineering Research Department, Isfahan Agriculture and Natural Resource Research and Education Center, AREEO, Isfahan, Iran

BACKGROUND AND OBJECTIVES: The stress caused by dryness can affect plant growth and physiology. Several coping mechanisms (recovery, avoidance, tolerance and drought escape) have been developed to mitigate the impact of drought stress, and  most strategies involve survival during stress condition. The aim of this study was to compare the morphological and physiological characteristics of two varieties of sorghum forage (Pegah and Speedfeed) under drought stress conditions in order to provide beneficial and functional recommendations to farmers in the study area.METHODS: This study was performed as a spit-plot plot in a complete randomised design with ۳ replications for two years in Esfahan, Iran. Experimental treatments included drought stress at three levels for two varieties of sorghum. Mechanisms of sorghum response to drought stress, including physiological and morphological  alterations, were also proposed. Treatment means were compared by the Duncan test at ۵% and ۱% levels of probability. The statistical analysis was applied to the data using the R software.FINDING: Lower irrigation showed a gradual decrease in plants height, number of leaves per plant, stem diameter, nitrogen and crude protein, with an increase in the length and weight of their panicle. Compared to Pegah variety, Speedfeed cultivar with ۱۲% increase enhanced the contents of chlorophyll (۱.۷ times) in the two years of experiment. It could be concluded that Speedfeed variety exhibited better yield and quality characteristics against drought stress compared to Pegah variety. Considering the tolerance index and the harmonic mean index, Pegah showed the highest sensitivity to drought stress.CONCLUSION: This study indicated that sorghum had several adaptive mechanisms for dealing with drought stress, so that it could be applied as a suitable alternative for other crops with higher water needs such as Zea.

Ash content, Crude Protein, Fodder, Sorghum, Nitrogen