Iranian Journal of Seed Research

Unfavorable storage conditions, especially relatively high environment humidity and high storage temperature greatly affect the quality of corn seeds. The effects of temperature, environment moisture and length of storage on six maize hybrids were examined. For the purpose of investigating germination traits, total soluble proteins, leakage electrolytes and the activity of antioxidant enzymes in maize hybrids, an experiment was carried out at the Agronomy and Plant Breeding Laboratory of Ilam University in 2016. The study was conducted as two factorial experiments, adopting a completely randomized design with three replications. The first factor comprised six maize hybrids (single crosses: 703, 706, 711, 604, Mobin and 701) that were obtained from Karaj Seed Breeding and Seedling Institute, Iran. The second factor was accelerated aging test in four levels involving non-aging (control treatment), aging for 4, 8 and 12 days under 40°C temperature and 95% humidity. The results showed that mean time to germination and electrolyte leakage significantly increased with aging duration. Mean time to germination and electrolyte leakage of the hybrids 701, Mobin and 711 increased more than the other hybrids. In addition, antioxidant enzyme activity decreased significantly with an increase in the aging period. These results indicated severe damage to cell membranes and enzyme activity in these hybrids. Moreover, there was a significant and positive correlation between germination percentage and the enzyme peroxides, as compared with other antioxidant enzymes. Although antioxidant enzyme activity exhibited a significant reduction in seed deterioration, nonetheless, generally speaking, compared with other varieties, KSC 703 was more tolerant.

Extended abstract
Introduction: A wide range of deteriorative conditions (especially moisture content and temperature) may affect seed quality during storage which may lead to seed aging. As the most important component of the phenylpropanoids pathway, trans-cinnamic acid, found abundantly in plants and its endogenous levels is influenced by stress conditions. The present study was conducted to investigate germination features, seed reserve mobilization, electrolyte leakage and malondialdehyde content in aged cowpea seeds affected by different concentrations of cinnamic acid.
Materials and Methods: The research has been performed in the laboratory of Faculty of Agriculture, Shahrood University of Technology, Iran. The experiment was designed as a factorial (two factors of the experiment included two levels of seed quality including non-aged and aged seeds and five levels of cinnamic acid concentrations including 0, 15, 30, 45 and 60 µM) based on a completely randomized design. Accelerated aging was applied as an efficient method to mimic storage conditions in the presence of accelerating factors. Cowpea (Vigna unguiculata) seeds (Bastam local variety) were incubated in a relative humidity of 95% and a temperature of 43 °C for 72 h to accelerate aging. Both seed lots were treated with 5 different concentrations of cinnamic acid for 6 h followed by standard germination and vigor tests. Data of germination and vigor tests were processed using the GERMINATOR software. Heterotrophic growth, seed reserves mobilization, electrical conductivity and membrane lipid peroxidation were assessed using the available methods.
Results: In this study, cowpea seeds responded to cinnamic acid differently based on their primary quality. In deteriorated seeds, concentrations of 45 µM and 60 µM could successfully enhance seed germination percentage, as compared with the aged seeds (i.e., control). A concentration of 45 µM also improved the vigor of deteriorated seeds. Seed pretreatment of 15, 30 and 45 µM enhanced seed reserves utilization in non-aged seeds. Aging negatively affected area under curve, germination uniformity and seedling dry weight of the deteriorated seeds. Application of 30 µM cinnamic acid improved germination uniformity. The area under the curve was positively affected by 15µM and 30µM. Concentrations of 45 µM and 60 µM enhanced seedling dry weight. Applying 45 µM cinnamic acid decreased electrolyte leakage by 38% and improved efficiency of seed reserves mobilization. Moreover, seed malondialdehyde content, as an indication of membrane lipid peroxidation, showed a sharp decline by applying increased concentrations of cinnamic acid.  
Conclusions: Based on our results, cowpea seeds respond to cinnamic acid differently based on their primary quality. These results imply that seed pretreatment with 45 µM cinnamic acid may successfully invigorate aged cowpea seeds. We also conclude that cinnamic acid application cannot improve physiological traits and can be regarded as a potent antioxidant in the invigoration of the aged seeds.
 
Highlights:

1. This is the first study focusing on the role of cinnamic acid in alleviating deterioration in aged seeds.
2. Cinnamic acid has been introduced as a robust antioxidant, which is effective in reducing the deleterious effects of seed deterioration.

Extended Abstract
Introduction: Soybean (Glycine max (L.) Merrill) is the primary source of vegetable oil. Even in desirable conditions, soybean seeds lose their viability in long term storage. Many factors contribute to seed deterioration, including genetic factors, mechanical damage, relative humidity, storage temperature, seed moisture content, existence of microflora, and seed maturity, which reduce seed quality and make seeds unfit for cultivation purposes.
Materials and Methods: In order to investigate the effects of seed deterioration on seed germination and also the effects of salicylic acid and ethylene on the improvement of deteriorated seeds of G. max., accelerated aging test for 0, 6 and 10 days and natural aging test for 6 months were conducted. After aging conditions, seeds were imbibed with 50 µM salicylic acid and 10 µM ACC (precursor of ethylene) for 6 hours at 25 °C. In addition, after natural and accelerated aging tests, a bunch of seeds was used without any hormonal treatment (i.e., dry seeds) as control seeds. The seeds’ germination percentage, total sugar, fructose, and glucose were investigated. Moreover, the gene expression of GAI1 and LOX1 was measured on dry seeds and under imbibition of water, salicylic acid and ACC at 6, 12 hours using Q-RT-PCR method.
Results: The germination results showed that increasing number of aging days led to a decrease in germination. Total sugar content in seeds aged for 6 days did not have a significant difference, as compared with non-aged seeds. However, total sugar content in seeds aged for 10 days was significantly higher than non-aged seeds. Increasing accelerated aging levels from 0 days to 10 days led to increases in glucose and fructose contents in dry seeds. In addition, genes exhibited different expressions in different days and hours. Increasing aging from 0 days to 10 days led to increases in GAI1 gene expression. Moreover, LOX2 expression increased in accelerated aging from 0 to 6 days. LOX2 gene expression in naturally dried aged seeds also increased and was higher than that in non-aged seeds. SA and ACC had different effects on measured values.
Conclusion: In general, it can be concluded that the deterioration of seed quality and vigor result from numerous degradation processes and disruption in seeds’ physiological activity. This study showed that aging is associated with an increase in total sugar, glucose and fructose levels. In addition, the expression of the genes involved in the germination is also affected. Increases in LOX2 gene expression were observed in both accelerated aging and natural aging pathways. GAI1 gene expression increased in accelerated aging. However, in normal aging, it decreased.
 

Highlights:

1. Identifying the role of LOX2 and GAL1 genes in soybean seed deterioration.
2. Investigating seeds’ physiological responses under natural and laboratory aging conditions.

Extended Abstract
Introduction: Providing important and effective elements such as zinc and boron- especially in areas where the soil for some reason cannot meet the needs of the plant- will be a good solution to improve seed and seedling quality and nutrition, and community health status. A considerable part of the wheat producing regions in the country are faced with late season haet during seed development stages. Thus, the present study will investigate the effect of heat stress and mother plant nutrition with zinc and boron micronutrients on seed deterioration and physiological quality of wheat seedlings.
Material and Methods: In a field experiment, wheat seeds were planted on two suitable planting dates (November 20) and late (January 5) to apply late-season heat stress during the seed development stage with three replications in Ramhormoz, Iran. The nutrition of mother plants with zinc and boron elements was done at three levels (nutrient-free and application of zinc and boron) as a foliar application. After harvest, the seeds were transferred to the laboratory and membrane integrity of seed cells was investigated using an electrical conductivity test as an indicator of deterioration. Another part of the seeds was planted in a factorial pot experiment based on RCBD with three replications to evaluate the quality of seeds and seedlings in the greenhouse.
Results: The results showed that exposure of seeds to heat stress during development reduced seed quality as well as seedlings so that the cell membrane in the seeds produced under heat stress conditions was damaged and their electrical conductivity increased by 19%. Also, these seeds showed more sensitivity to deterioration. The percentage of seedling emergence in the stressed seeds decreased by 21.66%. Heat stress also reduced seedling quality indices such as chlorophyll content, shoot dry weight, and root dry weight. Application of zinc and boron on the mother plant not only led to improved quality of seeds and seedlings under normal conditions but also the negative effects of heat stress on seed and seedling quality were reduced. There was a significant negative correlation between the seed electrical conductivity test and qualitative parameters. Therefore, the use of this test is recommended to determine the quality of seeds, especially seeds produced under late-season heat stress conditions.
Conclusion: Noting the negative effect of heat during seed development on seed quality, planting dates should be adjusted as much as possible so that the seed development stage does not coincide with the late-season heat stress. Due to the beneficial effects of using zinc and boron in the mother plant on many traits related to the quality of seeds and seedlings, their application- especially zinc- in soils with deficiency or the possibility of heat stress at the end of the season is recommended.

Highlights:

1. Zinc and boron micronutrients were used to mitigate the harmful effects of heat stress on seed quality.
2.  Physiological characteristics of seedlings obtained from seeds produced in the field under late-season heat stress conditions were investigated.