This study was conducted to evaluate the alterations of some morphological and biochemical parameters of sunflower cultivars ('08-TR-003', 'TR-3080' and 'TARSAN-1018') under salt stress. For this aim, the seedling of sunflower cultivars was irrigated with tap water as a control, and with salinized water with 50, 150 and 250 mM NaCl for 30 days under controlled conditions. Salinity caused an apparent reduction in morphological parameters (plant height, leaf area, fresh weight, dry matter and water content) in all cultivars. Salt stress significantly (P<0.01) reduced the activity of glutathione reductase (GR) and ascorbate peroxidase (APX) activities in all sunflower cultivars expect for superoxide dismutase (SOD) activity. According to our results, SOD seems to play a key role in the antioxidative process in salt treated sunflower plants. Proline and MDA contents were significantly (P<0.05) increased under salt stress in all cultivars. Among the cultivars, 'TR-3080' had greater values in terms of morphological (plant height, leaf area, fresh weight, water content) and biochemical (GR, APX and SOD (secondly) activities and proline contents) parameters. In the light of these findings, cv. 'TR-3080' seems to be less affected by salt stress.
Yield in agricultural production decreases due to biotic (diseases and pests) and abiotic (salinity, drought, high temperature, etc.) stress factors. Chemical methods have been widely used to fight against biotic stress factors. However, the use of chemicals in agriculture causes extra financial cost and environmental pollution. Improvement of high yielded cultivars via plant breeding methods does not seem to be adequate for meeting food demand of increasing population. That is why, the improvement of environmentally friendly new methods for high yield is obligatory. Leaves in plants form an active surface for photosynthesis. High photosynthetic activity affects yield directly by increasing matter production. The aim of this study was to increase seed and oil yields in sunflower via leaf defoliation. Oil-type sunflower cultivars used in the study, "08-TR-003," "TR-3080," and "TARSAN-1018," were obtained from the "Trakya Agricultural Research Institute." When plants reached to "star-shaped head stage," which is the beginning of the reproductive period, four different defoliation treatments were performed. They were control (no leaves removed), two leaves removed, four leaves removed, and six leaves removed. Half of the leaves were removed from just below the head, while the other half was removed from the middle part of the plant. After harvest, seed yield per plant, seed yield per decare, crude protein percentage, crude oil percentage, crude protein yield per decare, and crude oil yield per decare were determined. At the end of the study, it was observed that the application of defoliation, compared to the control, affected all characteristics positively.
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