Effect of Potassium Fertilizer application on Growth, Sodium and Potassium Uptake and some Physiological Characteristics of Pistachio Seedlings under Salinity Stress

Salinity is one of the growth-limiting factors for pistachio (Pistacia vera L.) crop production in semiarid and arid soils of Iran. Salinity poses two major threats to plant growth: osmotic stress and ionic stress. In addition, it also manifested an oxidative stress. The deleterious effects of salinity affect different physiological and metabolic processes of plants. The uptake of high amounts of salt by the plant leads to the increase of the osmotic pressure in the cytosol. Under this condition compatible osmoprotectant, such as proline and soluble sugars, is produced to protect the cells against the adverse effects from salt stress. High accumulation of proline is associated with tolerance to stress. Na+ and K+ homeostasis plays a vital role in the growth and development of higher plants under salt conditions owing to potassium–sodium (K+–Na+) interaction and is often associated with K+ deficiency. Application of potassium fertilizer affect plants growth and tolerance under salinity stress. The potassium is indispensable for several physiological processes, including the maintenance of membrane potential and turgor, enzyme activation, stomatal movement, regulation of osmotic pressure. Therefore the objective of this study was to evaluate the effect of potassium sulfate fertilizer application on growth, photosynthetic pigments, proline, soluble sugar and Na and K Uptake by Badami-riz Zarand P. vera L. (the main pistachio rootstock in Iran’s pistachio plantation area) seedlings under salinity stress.

This study carried out in greenhouse condition as a factorial experiment based on a completely randomized design and in three replications. Experimental factors was salinity of irrigation water (in three levels including 0.65, 5 and 10 dS m-1) and potassium sulfate fertilizer application )in three levels including without application or control, 150 and 250 mg kg-1 soil). Pistachio (Pistacia vera L. cv. Badami-riz Zarand) seeds were surface sterilized with solution of sodium hypochlorite in distilled water. Seedlings were transplanted in plastic potscontaining 10 kg of soil. The pots were maintained in the greenhouse under 25 ± 4 ◦C temperature and under natural light. The mean relative humidity was 40 %. At the end of growth period (six mounth), the plants were harvested and leaf area, root dry weight, shoot dry weight, chlorophyll a and b, total chlorophyll, carotenoids, proline, spluble sugar, root and shoot K and Na concentration were measured. In addition, the K and Na uptake in shoot and root, as well as K/Na ratio were calculated. Analysis of variance (ANOVA) was performed using SAS program version 9.4 (SAS Institute, Cary, NC). Significant differences of the mean values (P <0 .05 for F-test) were determined by Duncans’s Multiple Range Test.

Results indicated that with increasing salinity stress, leaf area, root, and shoot dry weight, chlorophyll content and shoot and root K uptake decreased, while carotenoids and shoot and root Na concentration increased. The highest and lowest value of leaf area, root, and shoot dry weight, chlorophyll content and shoot and root K uptake were observed in control and high salinity levels (10 dS m-1) treatments respectively. Application of potassium sulfate fertilizer at both levels (150 and 250 mg kg-1) led to a significant increase in leaf area (8.1 and 8.7 % respectively), root dry weight (21.2 and 20.0 %), shoot dry weight (21.3 and 19.9 %), total chlorophyll (10 and 7.8 %), carotenoids (32.2 % and 35.7), proline (21.1 and 14.4 %), root K concentration (44.1 and 56.2 %), shoot K concentration (11.0 and 26.9 %) and K uptake in root and shoot. in high salinity treatment seedlings showed higher Na+/K+ ratio in the roots than that of the shoots. In addition, application of potassium sulfate fertilizer decreased Na uptake in shoot and root. Moreover, the addition of potassium fertilizer increased K/Na ratio in the shoot and root. The results also indicated there were no significant difference between potassium sulfate fertilizer levels (150 and 250 mg kg-1) effects on investigated traits.

It could be concluded that application of potassium sulfate fertilizer results in reduce the negative effects of salinity stress and subsequently enhance tolerance to salinity stress and improved P. vera L. seedlings growth. Therefore, nutrient management of potassium can be considered for decline of negative effects of salinity in P. vera L. v. Badami-riz Zarand seedlings.