The Growth and Physiological Characteristics of Three Commercial Rootstocks of Pistachio (Pistacia vera L.) Under Controlled Temperature Conditions

In recent decades, global warming causes climate changes which triggers physiological and nutrition disorders in plants. Iran is a main pistachio producer in the world. Pistachio cultivar is mainly grafted into seedling rootstocks are which obtained from especial cultivars and wild type pistachio. The changes in the vegetative growth and yield in pistachio orchards have been obviously observed in the years with so warm or so cold weather conditions. The purpose of this research was evaluating the effects of temperature on the growth of three pistachio rootstocks. In order to study the effect of temperature on the growth and physiological characteristics of three commercial pistachio rootstocks, a factorial experiment on the basis of a completely randomized design (CRD) was carried out with three replications. The first factor was three rootstocks including: Pistacia vera cv. Badamie-zarand, P. vera cv. Ghazvini and P. vera var. Sarakhsi and the second factor was four temperature conditions including: 10, 15, 20 and 25 degrees Celsius. Pistachio seedlings after planting up to 15-leaf stage were kept in the greenhouse condition and then the pots were transferred to growth chambers which adjusted to defined temperature treatments. The plants were kept in temperature treatments for fifteen days. At the end of experiment, growth parameters including fresh and dry leaf weight, fresh and dry weight in shoot and root and leaf area and physiological parameters including stomatal conductance, relative water content of leaves and leaf chlorophyll index were measured. The statistical analysis was done using SAS 9.1 software and mean comparison was done by using the lowest significant difference test (LSD). The results showed that with increasing environmental temperature, an increase in the number of leaves, stem height, dry weight of leaf, stem and root, leaf area was observed in pistachio rootstocks. There were significant differences among rootstocks in most of the growth parameters. Badamie-Zarand was more vigorous than the other rootstocks in low temperature. The highest SPAD index was observed in high temperature environment (20, 25°C) beside lowest SPAD index level was observed at Low temperature environmental (10, 15°C). Minimum and maximum stomatal conductance was respectively obtained at 10 and 25 °C in Sarakhsi rootstocks which reveals the sensitivity of this rootstock to temperature fluctuations. In contrast, stomatal conductance variations in the Ghazvini rootstocks are lower than the other rootstocks when exposed to different environmental temperature. This may show the tolerance of this variety to changes of environmental temperature conditions. The leaf RWC in three pistachio rootstocks at different ambient temperatures shows a significant difference. At 15 and 20°C, Ghazvini rootstock has the highest RWC and Badamie- Zarand rootstock has the lowest levels of RWC. The highest relative water content was obtained at 10°C in Sarakhsi rootstock and at 25°C in Badamie-Zarand rootstock. Positive correlation between root dry weight and stomatal conductance reflects the rootstock compatibility with ecological conditions. Badami Zarand rootstock has more vegetative growth in low temperature environment and more adaptation to a wide range of temperature in comporison to two others rootstock and also can be recommended to nursery as a rootstock for planting.