Effects of nano zinc oxide and soil salinity on contribution of stem reserves in grain yield, leaf appearance rate and some growth indices of barley (Hordeum vulgaris L.)

Introduction Salinity is one of the major abiotic environmental stresses, which affect almost every aspect of plant life and significantly reduces crop yield. Thus it is a serious threat to agricultural productivity especially in arid and semi-arid regions. The response of plants to salinity depends on several factors such as developmental stage, severity, duration of stress, and cultivar genetics. Several strategies have been developed in order to decrease the toxic effects caused by high salinity on plant growth. Among them use of microelements such as zinc plays a very important role in yield improvement. Zinc is an essential micronutrient for humans, animals and plants, which act as the metal component of enzymes or as a functional structural. A number of researchers have reported the essentiality role of zinc for plant growth and yield. Zinc is required for chlorophyll production, pollen function, fertilization and germination plays an important role. So, recent researches have shown that a small amount of nutrients, particularly Zn applied by foliar spraying can affect the susceptibility of plants to stress. Zinc (Zn) is known as an important micronutrient and its deficiency is recognized as a critical problem in plants, especially grown on saline conditions with high pH values.   Materials and methods In order to study of effects of foliar application with Nano zinc oxide on contribution of stem reserves in grain yield, leaf appearance rate and some growth indices of barley (Hordeum vulgaris L.) in various levels of soil salinity, a factorial experiment based on randomized complete block design with three replications was conducted at research greenhouse of faculty of Agriculture, University of Mohaghegh Ardabili in 2012. Experimental factors were included soil salinity in four levels (no salinity, salinity of 25, 50 and 75 Mm) with NaCl and foliar application of Nano-Zinc oxide at four levels (0 as control,0.25, 0.5, 0.75 and 1 g/lit).   Results The results showed that increasing of soil salinity decreased yield, leaf appearance rate and growth indices of barley. It was vise versa in foliar application of Nano-Zinc oxide. Maximum of dry matter remobilization from stem and aerial vegetative organs was obtained in salinity of 75 Mm× no foliar application of Nano-Zinc. Means comparison showed that maximum of yield (1.22 g per plant), leaf appearance rate (0.466 leaf/ day) and growth indices were obtained in 0.75 g/lit of Nano-Zinc oxide× without of salinity application and minimum of they were obtained in no foliar application× soil salinity of 75 Mm. It seems that in order to increasing of yield and some growth indices such as total dry matter, crop growth rate and relative growth rate under salinity condition, can be suggested that be applied 0.75 g/lit of Nano-Zinc oxide.