Effects of Gibberellic Acid and Nitrogen on Some Physiology Parameters and Micronutrients Concentration in Pistachio under Salt Stress

Salinity is one of the main problems which limits crop production, especially in arid and semi-arid areas such as Iran. Iran is the most important producer of pistachio in the world. However, its performance is low in many areas. Most pistachio plantations are irrigated with saline water and with low quality (28). On the other hand, nitrogen is a dynamic element which is a constituent of amino acids, proteins, nucleic acids and Enzymes and it has a vital role in plant physiology, growth, chlorophyll formation and production of fruit and seeds (34). Gibberellic acid is known as phytohormon which varied physiological responses in plants under stress. acid gibberellic increases the photosynthesis and growth under stress and impact on the physiology and metabolism of plant (29). Based on previous studies, production and activity of plant hormones are affected by natural factors and plant nutrient requirements and the nitrogen has an important influence on production and transmission of acid gibberellic plant shoot. Therefore, in this study the effect of acid gibberellic and nitrogen on some characteristics of physiology parameters and micronutrient pistachio seedlings (Cv. Qazvini) under saline conditions was studied.
Experiment under greenhouse condition and factorial in a completely randomized design with three replications was conducted in greenhouse agriculture college, Vali-E-Asr University of Rafsanjan. Treatments consisted of three levels of salinity (0, 1000 and 2000 mg of sodium chloride per kg of soil), three levels of nitrogen (0, 75 and 150 mg per kg of ammonium nitrate source) and three acid gibberellic levels (0, 250 and 500 mg per liter). Adequate soil with little available salinity conditions was collected from the top 30-cm layer of a pistachio-culture region of Kerman province. After air drying and ground through passing a 2 mm sieve, some of the physical-chemical properties of this soil include pH (7/63), Tissue (Sandy loam), electrical conductivity (ECe) (1 dS m-1), Silt (23.1%), Clay (5.5%), Organic matter (0.5%), Olsen phosphorus (P) (5.35 mg kg-1), Ammonium acetate-extractable K (100 mg kg-1) were determined. Nitrogen treatments 3 weeks after planting, dissolved in irrigation water was added to pots. Salinity, after the establishment of the plant (5 weeks after planting), divided into two equal parts and one-week interval dissolved with irrigation water was added to the pot. as well acid gibberellic treatments, as spray after salt treatment was applied at three times and at intervals of one week.
The results showed that the salinity content of carotenoid and Chlorophyll fluorescence parameters significantly reduced but with increasing acid gibberellic and nitrogen application, mentioned parameters were significantly increased, compared to controls. The ability of photosynthesis improved and increased productivity. Mozafari et al studied the pistachio, reported that with increasing salinity from zero to 150 and 300 mM NaCl, carotenoids decreased more than 16% and 22% compared to control respectively. Carotenoids play a most important role in light, protecting plants against stress condition. Salinity application increased leaf proline, but with application of 150 mg nitrogen and 500 mg per liter foliar application of acid gibberellics, this parameter increased by 55 and 26 percent, respectively. Also, combined use of these two treatments increased proline content by 79 percent compared to control. The researchers stated that the increasing gibberellin concentration caused leaf proline increased, so spraying 100 and 200 mg per liter gibberellin significantly increased leaf proline compared with the non-application of gibberellin. The results also showed with increasing salinity increased iron, manganese and zinc concentrations shoots and roots and decreased copper concentrations, but using 150 mg of nitrogen and acid gibberellic consumption concentrations of copper element increased. Hojjat nooghi and Mozafari (28) reported, the used salinity of 60 mM NaCl increased shoot Fe concentration, but by applying the same amount of salinity in the root iron concentration decreased compared with the control. Research has shown that the copper concentration in the leaves and shoot of corn planted in soil decreased with increasing salinity. Micronutrient absorption reduction such as copper in salt condition can result in greater absorption of nutrients such as sodium, magnesium and calcium. The researchers in the study reported that with increasing nitrogen in the form of nitrate and ammonium, zinc concentration in plant tissues increased along with increasing salinity and lower shoot dry weight, zinc concentration was increased in two wheat cultivars too.
The results of this experiment showed that under saline conditions, acid gibberellic and nitrogen applied alone or in combination improved physiology parameters and increased nutrient concentration of pistachio seedling.