| چکیده انگلیسی مقاله |
Introduction: Seed deterioration is a major problem in agriculture. A considerable part of the seed production was lost as a result of deterioration. Seed deterioration is an inflexible and irreversible process. Seed deterioration is associated with oxidative stress and the uncontrolled accumulation of reactive oxygen species. Seeds have a group of enzymatic and non-enzymatic antioxidants that protect them against reactive oxygen species and help maintain seed vigor and support seed germination processes. The response of different cultivars to seed deterioration is different. Knowing the sources and mechanisms of deterioration and how different cultivars respondent can help to select the appropriate cultivar for the region and also provide useful information in selecting and applying appropriate management methods for storage and increasing the storage time of seeds. Materials and Methods: This experiment was conducted to study the deterioration mechanisms of rice (Oriza sativa) seeds in natural storage and accelerated ageing in 2017 and 2018. The Experiment was in factorial on the basis of completely randomized block design arrangement with three replications. Treatments were 1 and 6 months natural storage (4˚C, the moisture content of seed were 11 %, and 60 % RH) and accelerated ageing (96 hours in 45˚C and 100 % RH) in four cultivars including Hashemi, Gilaneh, Khazar and Domsiyah. Germination percentage, germination rate, shoot length, radicle length, shoot dry weight, radicle dry weight, shoot vigor index (SVI), -αamylase activity, catalase (CAT), peroxidase (POX), superoxide dismutase (SOD) activity, malondialdehyde (MDA) and hydrogen peroxide (H2O2) content were investigated. Results: The results showed that germination percentage, germination rate, shoot length, radicle length, shoot dry weight, radicle dry weight, shoot vigor index (SVI), -αamylase activity reduced in all four cultivars due to accelerated ageing and storage of seeds for six months. This decrease was accompanied by an increase in the free radical content of MDA and H2O2 and a decrease in the activity of the antioxidant enzymes SOD and POX. MDA content was more in the seeds of six months storage. The activity of CAT increased after deterioration treatment, this increase was more in the seeds of six months storage. These seeds also showed lower H2O2 content compared to accelerated aging seeds. Khazar cultivar showed lower H2O2 content as a result of higher CAT enzyme activity. Moreover, this cultivar showed a better germination percentage and germination rate after deterioration treatment compared to other cultivars. The decrease in germination percentage due to deterioration in Domsiyah was very severe (21.4 % and 69 % decrease after six months of storage and accelerated aging in 1396, respectively, and 20.53 % and 64.9 % decrease after six months of storage and accelerated aging in 1396, respectively). This cultivar showed the lowest germination percentage, germination rate, seed vigor, and -αamylase activity in accelerated aging treatment. Also, the lowest SOD activity and the highest H2O2 content were observed in this treatment. Gilaneh and Hashemi cultivars showed higher germinability, α-amylase activity, and SOD and POX at the beginning of the experiment, but after deterioration treatment, their germinability, decreased along with the activity of antioxidant enzymes. Conclusions: In all studied cultivars, the accelerated aging and storage of seeds for six months showed adverse effects on germination rate. This decrease was accompanied by an increase in free radicals in the seeds and a decrease in the activity of antioxidant enzymes SOD and POX, which were less severe in Khazar cultivar and more severe in Domsiyah cultivar. These results indicate the more important storage conditions in Domsiyah cultivar. |