The effects of zice fertilizer on some physiological characteristics of chickpea (Cicer arietinum L.) under water stress

Dehydration is one of the limiting factors of crop production. It results from increasing the amount of water losses from leaf or inadequate water absorption rate or combination of both. Zinc used in many enzymes of the plant tissues and have catalytic role in activation of some enzymes. Zinc is involved in the synthesis and degradation of proteins and is an essential micronutrient for normal growth and reproduction of crops. It plays an important role in the synthesis of protein and carbohydrates, metabolic functions of the cell membrane to protect cells against free radicals of oxygen and other processes related to the plants adaptation to stress. Osmotic adjustment is one of the most important mechanisms of drought tolerance in plants. By this mechanism the osmotic potential of plant cells reduces by solute accumulation. Torgur potential maintains high which is essential in cell development and growth.
Effect of water deficit stress and foliar application of zinc on physiological characteristics of chickpea was studied at a factorial experiment using randomized complete block design in field crop research station of University of Mohaghegh Ardabili in 2012. Irrigation schedules consisted of three levels (1: irrigation at planting, 2 : planting before flowering and 3 : planting before flowering pod set) and zinc was applied on three concentration (0, 3 and 6 kg ha-1 as zinc sulfate) in two stages of 15 and 25 days after planting. In this study Proline, Lysine, Methionine, soluble sugars, and protein content were measured in three stages 33, 55 and 75 day after stress induction and osmotic potential in 75 days after stress. Osmotic potential was measured based on the electrical conductivity, the extraction of soluble sugars by using phenol sulfuric method, total protein from the leaves by the Bradford method and Lysine and methionine assayed using Ferrel method. Data were analyzed using the SAS and means compared by the LSD at the 5% level.
The results showed that dehydration increased proline, lysine, methionine, protein and soluble sugar content but reduced the osmotic potential. The maximum amount of proline accumulation resulted in two and three stage samplings once irrigation and its minimum rate obtained in the three irrigation schedule. It seems that by reducing soil moisture availability or increasing irrigation intervals, the water potential of the cells has been reached to the lower threshold which enhanced the protease enzyme activity resulted in proline accumulation in order to enhance water absorption. The maximum amount of lysine during 55 and 75 days after the stress obtained from one irrigation. Unlike the lysine, methionine content reduced during stress period, so that it's maximum value was obtained over 55 and 75 days after the tension of 3 times irrigation. Dehydration reduced the amount of proteins so that the maximum amount of protein production observed with three irrigations. Spraying six kg ha-1 zinc sulphate also enhanced the amount of proline, soluble sugar and osmotic potential but had no effect on the amount of lysine and methionine. Correlation showed that by increasing the time from withholding irrigation by 33 days proline increased, but osmotic potential affected only after 75 days. The regression results also showed that in the early stages of sampling, proline content had the significant effect on the biomass prediction but the elapsed time increased the effect of lysine, methionine and protein on predicting the osmotic potential.
In general it can be said increasing the secondary metabolites production can reduce the stress and proline is the most sensitive to the low level of stress, but under higher levels of stress many metabolites such as lysine and methionine were also used for osmoregulation. The regression results also showed that in the early stages of sampling, proline levels had the largest effect on the biomass prediction, but with increasing time the lysine, methionine and protein levels also predicted the osmotic potential.