Effect of salt stress on yield and yield components in chickpea (Cicer arietinum L. cv. Azad)

Introduction One of the important abiotic stresses is salinity, with adverse effects on yield and product quality. Salinity damages to plants through ionic and osmotic stress are reflected in loss of water content, specific toxicity effect of ions, and disruption in nutrients uptake. Soil salinity can be raised by irrigation, inappropriate drainage, sea advancement to coastal regions and accumulation of salts in desert and semi-desert regions. Salinity is a limiting factor for plant growth because it limits the feeding of the plants by reduction the uptake of P, K, nitrate and Ca and increasing inter-cellular ion concentration and osmotic stress. In addition to its adverse impacts on the yield and yield components of crops, salinity affects most processes involved in the growth and development of the plants too.   Materials & Methods  The present study was conducted in research greenhouse of Department of Agriculture, Birjand University on the basis of a Randomized Complete Block Design with four replications. The soil salinity treatments included five levels of 1, 3, 5, 7 and 9 dSm-1. Soil texture was loam-sandy with the pH of 8.09 and EC of 1 dSm-1. The irrigation water was filtered with EC<350 μScm-1. The salinity was applied in accordance with soil saturation moisture percentage and field capacity moisture percentage. NaCl was used as the source of salinity. Irrigation was applied by daily weighing of pots in terms of field capacity moisture percentage. In flowering before yellowing of chickpea pods, number of leaves, leaf area and the concentration of sodium and potassium were measured. After full yellowing of the plants, pod number, grain yield, 100 grain weight and total dry weight per plant was recorded.   Results & Discussion It was found that salinity level significantly influenced all measured traits. Salinity adversely affected plant height, number of leaves and leaf area, so that the highest level of salinity resulted in 22.4% plant height, 15.8% number of leaves and 58.4% leaf area per plant. The salinity by reducing the water-absorbent, creates an imbalance in nutrient uptake and toxic effects of some ions and causes changes in the metabolism of plants and reduces their growth. Reduction in the number of leaves and leaf area, which in fact have been a reduction in the photosynthesis area can be one of the factors that reduce the dry weight of plants. Under salinity stress, the plants reduce their leaf area to counteract the stress and results in greater thickness of the leaves, the accumulation of more chloroplast per unit leaf area and increase in leaf chlorophyll content. Salinity enhanced the concentration of sodium, reduced concentration of potassium and concentration K:Na in chickpea. It was revealed that the increase in salinity level from 1 to 9 dS m-1 increased the concentration of sodium 76.75% and reduced concentration of potassium to 59.7%. Rising the entry of sodium into plant under salinity conditions cause cytoplasm to be replaced with potassium ions and ion toxicity effect. By increasing the amount of sodium or sodium ratio to potassium in root environment, the concentration of potassium in plant tissues was reduced. Also, the highest salinity levels as compared to control reduced pod number by 33.33%, grain yield by 59.83%, 100 grain weight by 44.44% and by 39.34% total dry weight per plant. Shoot dry weight loss as a result of salinity can be attributed less number of leaves and smaller leaves. One effect of salinity on grain yield is changing 1000-grain weight. Lower 1000-grain weight cane be associated with shorter grain filling period in salinity treatments and also with lower synthesis of assimilates. On the other hand, the change in the pathway of assimilate partitioning to roots for counteracting the salinity can be another reason for lower dry weight of the grains.     Conclusion The effect of different levels of salinity on the measured traits showed that salinity had negative impacts on morphological traits, plant height, number of leaves, leaf area, potassium concentration and concentration ratio of potassium to sodium. Sodium concentration in plants reduced dry matter accumulation in chickpea and grain yield. Application of these levels of salinity indicated that peas are moderately sensitive plants to salinity, particularly salinity stress level of >7 dS m-1.