Iranian Journal of Seed Research

Seed quality is one of the most important factors affecting seed germination and seedling growth. In order to investigate the effects of seed aging on germination and seedling growth of sunflower cultivars, a factorial experiment was conducted based on a completely randomized design with three replications in seed research laboratory of Shirvan Higher Education Complex. To create 7 different treatments of seed aging, seeds of three cultivars Ghasem, Farrokh and Barzgar (as the first factor) were kept at a high temperature (43◦ C) and high relative humidity (100%) for 0 (control), 24, 48, 72, 96, 120 and 144 hours (as a second factor). The results of mean comparison showed that germination percentage, rate and seedling growth of Farrokh cultivar was more than other cultivars in each aging level. Germination percentage, rate and uniformity, seedling dry weight, radicle and stem length reduced linearly with increase in the duration aging in all cultivars. Under the aging conditions, the time to beginning and ending of germination was significantly increased. Overall, it was concluded that seed quality of sunflower cultivars was seriously decreased under the aging conditions.

Application of zinc can improve the tolerance and resistance of plants especially sunflower to environmental stresses and be effective on kernel set and yield. To investigate the effects of zinc oxide nanoparticles on the length, effective period, the rate of kernel filling and kernel weight in sunflower cultivars, a factorial experiment based on randomized complete block design with three replications was conducted at the University of Mohaghegh Ardabili, Ardabil, Iran. Treatments were three sunflower cultivars as Aline 191, Aline 122 and Farrokh and three concentrations of nano zinc oxide including 0, 0.5 and 1 g lit^-1 which sprayed at three stages. Results showed that interaction of cultivar and nano zinc oxide was significant on kernel filling rate, the effective period of kernel filling, maximum kernel weight and duration of kernel filling. The rate of filling and maximum kernel weight increased with 0.5 g lit^-1 spraying of Nano zinc oxide in Aline 191 and 122, but in Farrokh cultivar was significantly reduced in comparison to the control. Also, no significant difference was found between 0, 0.5 and 1 g lit^-1 of nano zinc oxide on kernel filling rate, effective kernel-filling period and duration in Farrokh cultivar. In conclusion, foliar application of zinc oxide nanoparticles led to the improvement of kernel weight and their filling parameters and the more appropriate response was observed in foreign cultivars for this treatment, while final kernel weight decreased in Farrokh cultivar. Therefore, it can be used 0.5 g lit^-1 of nano zinc oxide for increasing grain yield in foreign cultivars of Aline.

Extended abstract
Introduction: Environmental stresses, including salinity, result in the overproduction of reactive oxygen species, which, at high levels, can cause oxidative damage, impair membrane lipid functions, inactivate enzymes, and impede the metabolic activities of the plant. Salinity affects seedling growth through osmotic stress, ionic toxicity, lack of absorption of essential elements and water, production of free radicals, cell membrane destruction, and reduction of cell division. Seed priming is a quick, easy, low-cost, and effective strategy for improving germination. It is a seed treatment before planting in which seeds are fully immersed in special solutions and dried until further use. Seed priming assists the germinating seed in mitigating saline stress by neutralizing ionic toxicity or by promoting defense mechanisms. This study aimed to assess the effect of seed priming with vitamin U (S-Methylmethionine) on germination and the physiological and biochemical characteristics of sunflower seedlings under salinity stress.
Materials and Methods: This experiment was conducted in 2023 as a factorial based on a completely randomized design with three replications at the University of Mohaghegh Ardabili. Experimental treatments included four salinity levels (0, 50, 100, and 150 mM) and three levels of vitamin U (0, 2, and 4 mM).
Results: The results showed that salinity reduced the germination and growth indicators, including Germination Rate (GR), Germination Percentage (GP), Mean Daily Germination (MDG), Seedling Length (SL), Seedling Dry Weight (SDW), Seedling Length Vigor Index (SLVI), and Seedling Weight Vigor Index (SWVI); but seed pretreatment with different levels of vitamin U, especially the level of 4 mM, improved these traits. Daily Germination Speed (DGS) was higher by about 25% compared with the control treatment without salinity and, in priming with vitamin U compared with the control (distilled water), it showed a decrease of about 32%. Compared with the control (distilled water), the catalase, peroxidase, superoxide dismutase activities, and proline content of seedlings obtained from primed seeds increased respectively by 9%, 8%, 32%, and 47% after vitamin U treatment. With increasing salinity levels, there was a reduction trend in total seed protein content (0.384 mg g^-1 FW), and the lowest total seed protein content was observed at salinity 150 mM. Mean Germination Time (MGT) and malondialdehyde content of seedlings in the priming with a concentration of 4 mM vitamin U and without salinity showed a decrease of about 73% and 21%, respectively, compared with the control (distilled water) and salinity 150 mM.
Conclusions: The results of this research showed that sunflower seed priming with vitamin U at a concentration of 4 mM is the most effective method to improve the germination and biochemical characteristics of seedlings, and stimulating antioxidant enzymes can reduce the harmful effects of salinity on some traits in sunflower seedlings and improve seedling growth.

Highlights:

1. Seed priming using vitamin U improved germination indices of sunflower seed under salinity.
2. Priming with vitamin U decreased the content of malondialdehyde and increased the amount of proline and protein.
3. The concentration of 4 mM vitamin U revealed a better effect on germination indices and biochemical characteristics.