Document Type : Research Paper
Authors
1 . Department of Plant Science and Medicinal Herbs, MeshginShahr Faculty of Agriculture, University of Mohaghegh Ardabili, Ardabil, Iran
2 Meshgin-Shahr Jihad Keshavarzi, Ardabil, Iran
Abstract
Objective: In safflower, a considerable proportion of photosynthates remains in vegetative organs and is not efficiently translocated to developing grains. Moreover, the occurrence of high temperatures during pollination and seed filling markedly reduces the yield potential of the crop. Improving the partitioning of assimilates from vegetative to reproductive sinks may enhance safflower performance under unfavorable environmental conditions. The present study aimed to evaluate the effects of abscisic acid and jasmonic acid on remobilization of stored photoassimilates and grain yield of spring safflower.
Methods: The experiment was conducted at the research farm of the Faculty of Agriculture of Meshgin-Shahr during the 2024 growing season. A randomized complete block design with three replications was used. Experimental treatments included: 1) irrigated plants without hormone application as control, 2) rainfed plants without hormone application, 3) irrigated plants sprayed with abscisic acid, and 4) irrigated plants sprayed with jasmonic acid. Both hormones were applied after completion of pollination in three consecutive sprays. Traits were measured at three developmental stages, namely the beginning of capitulum formation before spraying, the onset of seed growth one week after the last spray, and physiological maturity.
Results: At the beginning of capitulum formation, plant height and total biomass were greater in irrigated than in rainfed plants. In most cases, the experimental treatments did not show significant differences at the early stage of seed growth. Evaluation at physiological maturity indicated that rainfed conditions and application of abscisic and jasmonic acids significantly reduced biomass, capitulum weight, and number of seeds per plant compared with the control. The highest amount of remobilization was observed in plants treated with jasmonic acid. The value of this trait in the abscisic acid treatment, rainfed plants, and the control ranked next, respectively. The greatest grain yield per plant and harvest index were obtained from the irrigated control without hormone spraying. Rainfed conditions as well as external application of abscisic and jasmonic acids significantly decreased grain yield in comparison with the control plants.
Conclusion: It appears that the effect of applying abscisic and jasmonic acids on reduction of current photosynthesis and production of assimilates was much greater than their role in enhancing remobilization and improving partitioning of photo-assimilates to grains. There is a possibility that the use of these hormones after the first half of grain filling, when current photosynthesis declines, may lead to higher remobilization and better grain yield. Further studies under diverse environments are recommended to confirm these findings and optimize application timing.
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