the effects of drought stress on morphological traits and yield of three medicinal plants ( coriandrum sativum, foeniculum vulgare and anethum graveolens) in greenhouse conditions.

drought stress is one of the important problems in arid and semi_arid regions. drought stress take place in plants when available water is lesser than evapotranspiration. in order to evaluate the effect of drought stress on morphological traits and yield of three medicinal plants an experiment was carried out during the 2010 year in research greenhouse of faculity of agriculture, ferdowsi university of mashhad, in a factoriel arrengement based on a completely randomized block design with four replications. factors include 4 drought stress levels: field capacity (100%), 75%, 50% and fc25% and 3 medicinal plants include: coriandrum sativum, foeniculum vulgare and aniethum graveolens. the traits such as plant height, leaf number per plant, number of lateral branches per plant, umbrellas per plant, umbels per umbrellas, seed number per plant, seed weight per plant, 1000 seeds weight and harvest index were measured. results showed that decreasing content of water in soil lesser than field capacity had significant effects on all of these traits. coriandrum sativum in fc25% had maximum seed number in umbrellas(14 number), seed number per plant(27 number), umbrellas per plant(4 number), umbels per umbrellas(10 number) and 1000 seeds weight (6.5 gr). also foeniculum vulgare in fc25% had minimum seed number in umbrellas(2 number), seed number per plant(2 number). umbrellas per plant(0.25number), umbels per umbrellas(0.5 number) and 1000 seeds weight (0.15 gr). harvest index positive correlation with seed weight per plant and 1000 seeds weight.