effect of drought stress, corm size and corm tunic on morphoecophysiological characteristics of saffron (crocus sativus l.) in greenhouse conditions

in order to investigate the effects of corm tunic, corm weight and drought stress on saffron (crocus sativus l.), an experiment was conducted at the greenhouse of ferdowsi university of mashhad, iran. treatment were combination of four corm weights range (2-4, 4-6, 6-8 and 8-10 g), two levels of water availability (100% field capacity and drought) and two levels of corm tunic (natural corm with tunic and without tunic) as factorial arrangement based on completely randomized block design with three replications. the corms were divided to four groups based on their weights and removed tunics of corm in tunic free treatment. results indicated that the highest biomass produced in irrigation, corms with tunic with maximum weight. both chlorophyll a and b contents decreased significantly under drought stress and chlorophyll b content was 50% of chlorophyll a content. effect of corm size and corm tunic and interaction of these treatments imposed a significant effect on the leaf number per plant, leaf weight and chlorophyll content. effect of corm tunic in 8-10 g corm size increased ch (a)/ch (b) ratio and leaf number. the relative water content was decreased in drought treatment in both tunic and tunicless treatments and the best corm weight in all treatment was 6-8g and could be useful to tolerate drought stress.