INFLUENCE OF SILICON ON WHEAT GROWN UNDER SALINE ENVIRONMENTS

Abstract

Salinity often causes decrease and instability in wheat production that occupies a supreme position in food grains of Pakistan. Recently, wheat has been designated as silicon (Si) accumulator which can alleviate the salinity damage, a major constraint to agricultural crop production. With the objective to combat salinity stress in wheat by Si applications using calcium silicate, a series of experiments were conducted on two contrasting wheat genotypes (salt sensitive; Auqab-2000 and salt tolerant; SARC-5), under normal and saline conditions. Initially five different levels of Si (0, 50, 100, 150 and 200 mg L -1 ) were optimized for salinity tolerance on the basis of plant morphological characters especially dry weight in hydroponics and 150 mg L -1 was selected as an optimized level. Optimized Si-level was further used to investigate its effect on wheat in hydroponic and pot culture under normal (2 dS m -1 ) and saline (10 dS m -1 for hydroponics and 12 dS m -1 for pots study) conditions. The evaluation was done on the basis of various morphological, physiological, biochemical, growth and yield traits during these experiments. Silicon supplementation into the solution culture and soil medium significantly improved the K + : Na + with reduced Na + and increased K + uptake. Plant water relations with higher water potential and relative water content, increase in chlorophyll fractions and its ratios, enhanced stomatal conductance and better defense system with stimulated activities of superoxide dismutase (SOD) and catalase (CAT) were observed. Nevertheless, the activity of peroxidase (POD) was reduced and root growth remained unaffected by silicon application. The final field studies were conducted at two sites (within a radius of less than 500 m): Normal field with EC < 4 dS m -1 and saline field with EC~10-13.8 dS m -1 . Silicon was applied @ 0, 75 (half of optimized dose) and 150 mg kg -1 (optimized dose). Plants were harvested at maturity and concomitant increase in number of tillers, number of grains per spike, grain yield, and biological yield were observed due to silicon application both under optimal and salt affected field conditions. It was concluded that SARC-5 is better than Auqab-2000 under salt stress and silicon inclusion into the any growth medium is beneficial for wheat and can improve crop growth by maintaining plant water status, better K + : Na + and recovering the plant defense system adversely influenced by salt stress.