Effect of insufficient irrigation on plant dry mater and remobilization in three spring safflower genotypes (Carthamus tinctorius L.)

In order to investigate the effect of insufficient irrigation on remobilization percent and plant dry mater in three spring safflower (Cartamus tinctorius L.) genotypes, a field experiment was conducted at Research Farm, Faculty of Agriculture, the University of Birjand, Iran, during 2008-2009, as a spilt plot arrangement based on randomized complete block design with four replications. Irrigation regimes (full irrigation (whole season irrigation), irrigation until grain filling, irrigation until flowering, and irrigation until heading-bud) and genotypes (Mahali Isfahan (a local variety), Isfahan 28 and IL111) were arranged in main plots and subplots, respectively. Results showed that three safflower genotypes had different responses to different irrigation regimes in terms of total dry matter; leaf, stem and head dry mater in flowering and maturity stages, harvest index and percent of remobilization. With increasing duration of irrigation disruption, plant dry matter in all genotypes reduced, and reduction in these criteria in IL111 was the highest under conditions of irrigation until heading-bud. Furthermore, the share of remobilization to heads was increased by increasing duration of irrigation disruption. Among disruption irrigation levels, the highest and the lowest percentage of remobilization were obtained in irrigation until heading-bud and full irrigation stages, respectively. Moreover, IL111 genotype due to has higher harvest index, early maturity and increased senescence of leaves had the highest percent of remobilization from stem and other leaves. Based on the results, remobilization is an important way to compensate drought stress effects; it can be a proper characteristic of semi-dwarf cultivars in comparison with old cultivars. Grain yield can improve by increasing sink capacity which increase remobilization under terminal drought stress.