Potassium (K) scarcity of arable land is one of the important factors that hamper the growth of the plants and reduce yield worldwide. In the current study, we examine the physiological, biochemical, and metabolome response of Arachis hypogaea (GG7 genotype: fast-growing, tall, early maturing, and high yielding) under low K either solitary or in combination with Si to elucidate the ameliorative role of Si. The reduced fresh and dry biomass of peanut and photosynthetic pigments content was significantly alleviated by Si. Si application did not affect the leaf and stem K+, although it enhanced root K+ in K-limitation, which is probably due to up-regulated expression of genes responsible for K uptake. Si improves the
potassium use efficiency in K-limitation as compared to control. K-deficiency increased MDA, O2•-, and H2O2 levels in leaf and root of peanut. Si improved/maintained the activity of antioxidative
enzymes, which significantly lowered the ROS accumulation in K-limitation. The AsA/DHA and GSH/
GSSG ratio was approximately unaffected in both leaf and root, suggesting the maintained cellular redox potential in K-starved peanut. Si promotes accumulation of
sugars and
sugar alcohols,
phytohormones indicating their probable involvement in signal transduction, osmotic regulation, and improvement of stress tolerance. Down-regulation of
aspartic acid and
glutamic acid while up-regulation of
lysine,
histidine, and
arginine could maintain charge balance in K-deprived peanut. The significant accumulation of
polyphenols under K limitation supplemented with Si suggests the role of
polyphenols for ROS scavenging. Our results demonstrated that Si as a beneficial
element can mitigate K-nutrient toxicity and improve KUE of peanut under K-limitation conditions. Moreover, our results demonstrate that Si application can improve crop yield, quality, and nutrient use efficiency under nutrient limitation conditions.