The effect of priming on physiological and biochemical traits of French bean (Phaseolus vulgaris) under cobalt chloride stress

The germination stage ensures the durability, establishment, and final yield of plants.  The final density of plants per unit area is resulted when the planted seeds germinate fully and with adequate rate. Plants mainly undergo abiotic stresses that are a considerable constraint for agricultural production worldwide. Seed priming is one of the simplest and cheap methods to improve seed germination, acceleration of seedling growth and establishment, uniformity, reduction of flowering time, vigorous seedling production, etc which leads to improved quality and yield of crop under stressful and non-stressful conditions. This study aimed to investigate the effect of different types of priming on enzymatic and physiological changes of French bean seed under cobalt chloride stress conditions.

To examine the effect of priming on germination indices, the activity of antioxidant enzymes and proteins in French bean under cobalt chloride stress, a factorial experiment was performed in a completely randomized design with three replications. These factors included four levels: seed priming with 100 mg / l salicylic acid and mannitol, control and distilled water (no priming), and three levels of cobalt chloride stress (0, 100, and 200 mg / l).

The results showed that with increasing cobalt chloride concentration, germination indices (germination rate, root length, root fresh weight, stem fresh weight and stem dry weight) decreased. However, in the pretreatment of distilled water, salicylic acid, and mannitol there was a significant increase in germination indices (mean germination time, radicle length, plumule length, fresh radicle weight, and weight plumule) was observed. The interaction effect of priming and cobalt chloride caused an increase in radicle dry weight compared to control × stress treatment. The highest values of fresh radicle weight (14.4 g), dry weight of plumule (0.27 g), and plumule length (0.17 cm) were obtained in hydro priming pretreatment. The results also showed that hormone priming under stress conditions of 200 and 100 mg / l cobalt chloride increased protein content and polyphenol oxidase activity of French bean seedlings compared with the control treatment, respectively. Osmo priming increased the activity of catalase and peroxidase enzymes under stress and non-stress conditions resulted by 200 mg / l cobalt chloride.

according to the results of the present study, cobalt chloride reduced some physiological and biochemical traits of French bean seeds. However, the French bean has a relatively high cobalt chloride tolerance capacity, so that it showed good tolerance to different concentrations of cobalt chloride for up to 9 days.