Effect of zinc sulfate foliar application on morphological characteristics and yield of red beans (Phaseolus vulgaris L.) under different carbon dioxide- temperature and water stress

Climate change (temperature, rainfall and flood patterns, etc.) has major and negative effects on agricultural production and water and land resources. Part of climate change is to reduce soil fertility (through erosion processes), increase the frequency of repeated pest attacks, reduce crop yields, and increase groundwater harvest periods by reducing water access. Zinc plays an essential role in the basic processes of plant life, namely cell division, stomata regulation and respiration. Apart from the increase in carbon dioxide emissions, high temperatures are also a major stressor that can lead to severe growth retardation and plant distribution. At higher concentrations, carbon dioxide increased photosynthetic carbon and increased organic matter, which in turn increased stem diameter of lentil plant (Shams, 2017) .

The composite experiment was performed as a factorial experiment in a completely randomized design with four replications. Irrigation at three levels (60, 80 and 100% of field capacity) as the first factor, foliar application of zinc sulfate fertilizer at two levels (no foliar application and 0.5 gl-1) as the second factor and environmental conditions at four levels (380_24, 380_31, 700_24 and 700_31 C/PPm (carbon dioxide) were the third factor. The studied traits were number of root nodes, root dry weight, stem height and diameter, number of leaves and grain yield. Data were analyzed using SAS 9.1 software and the mean of the treatments was compared with LSD test at 5% probability level.

Co-application of carbon dioxide, complete irrigation and complete irrigation and zinc sulfate increased the number of nodes. Increasing the concentration of carbon dioxide under severe drought stress increased root dry weight. Also, increasing the concentration of carbon dioxide under mild environmental stress caused plant height, diameter and grain yield. Increasing the concentration of carbon dioxide in full irrigation conditions increased the number of leaves. Increasing carbon dioxide increases water use, photosynthesis and net primary productivity by reducing stomatal conductance and transpiration, which ultimately increases biomass and yield.Application of zinc sulfate under full irrigation conditions increased the total grain yield by 17.1 g/plant. Positive role of zinc in chlorophyll synthesis, and performance of optical photosystems can increase growth indices. The use of zinc chelate due to the role of zinc in the activity of plant enzymes and metabolisms, including plant hormones (auxin) has increased chlorophyll activity and photosynthesis, which finally has increased grain yield in the plant. 

Increasing the concentration of carbon dioxide at lower temperatures and full irrigation and mild stress increased the majority of morphological traits. Also, application of zinc alone and with full irrigation increased some morphological traits and grain yield.