Effect of deterioration on germination and enzymes activity in dry bean (Phaseolus vulgaris L. cv. Sadri) under salinity stress condition

Legumes are one of the most important crops to be effective in amending and fertilizing soils. Among legumes, bean, lentil, chickpea, broad bean and pea are most susceptible to salinity (Cobely, 1996). Abiotic stresses affect different aspects of plant growth, such as reduction and delay in germination, decrease in development rate, decrease in plant organs growth, decrease in plant life duration and finally decrease in dry matter production. Among abiotic stresses, salinity stress is considered to be the most influential type of stress in the production of legumes in the world and can greatly reduce production on many arable lands. One of the primary effects of salinity is the reduction of water content of plant tissues. Reducing water availability is due to an increase in the osmotic potential of salt in the root zone (Ghanbari et al., 2016). Seed priming is one of the methods for improving seed quality in which the seeds are exposed to water under controlled conditions, so that different metabolic and physiological activity occur at different levels of moisture inside the seed for germination before the radicle emergence and then seeds are dried to reach initial moisture (Farooq et al., 2006). To evaluate the effect of salinity and seed aging on germination characteristics of bean seeds, Sadri variety, a factorial experiment was conducted in a completely randomized design with four replications in Agriculture Laboratory, Faculty of Agricultural Sciences, University of Guilan in 2014. The treatments consisted of two groups of seeds (natural and aged) and five salinity treatments (0, 2, 4, 6 and 8 dS m-1). Before testing, seeds were disinfected with 10% sodium hypochlorite solution for 15 minutes (Ghanbari et al., 2016) and washed three times with distilled water. For aging, dried beans were exposed to a temperature of 41 °C and high relative humidity (100%) for 72 hours in an oven placed in a desiccator. Then, 25 seeds were put in each sterile petri dish with filter paper. To each petri dish, five milliliters of NaCl solution with potentials of 2, 4, 6, 8 dS/m were added and distilled water was added as control treatment. After applying the treatments, the petri dishes were covered with parafilm and were placed in the germinator at 25 °C in the dark for 8 days (Ghanbari et al., 2016). The results showed that there were significant differences between treatments for all the variables. In addition, the interaction of seed aging with salinity stress had highly significant difference at the probability level of 5% of plumule fresh weight and there were significant differences at the probability level of 1% for radicle and plumule dry weight, allometric index, seedling tissue water percentage and seed vigor, while regarding of means and percentage of germination and plumule length were not observed significant differences. Research on the effect of seed aging and salinity stress on bean germination characteristics showed that increasing the aging period and increasing levels of salinity stress negatively affected the bean germination characteristics and by the effect on plant water relations, toxicity due to ion accumulation, plasma reduction, molecular structure change of nucleic acids and decreased activity of enzymes eventually led to decreases in germination indices (Ghanbari and Karamnia, 2016). Increasing levels of salinity stress and aging the seeds reduced the activity of germination, mean time and germination percentage, and seedling growth. the results of seed deterioration can be destroyed the buildings the cell membrane with attack free radicals produced due to lipid peroxidation over the period deterioration noted. Therefore, seed aging and increase levels of salinity stress on the germination and its related factors in bean seed had a negative impact and through its impact on plant water relations, toxicity of ion concentration, reducing the plasma membrane integrity, change the molecular structure of nucleic acids and reduction of activity of enzymes eventually reduced the germination indices.