Effects of Si in nutrient solution on leaf cuticles

Abstract

The benefits of silicon for different plant species have been described in many studies in both soilless and traditional soil culture systems. The aim of this work was to quantify the effect of Si on leaf cuticles under different fertigation regimes and the relationship of this effect to water, potassium and nitrate absorption, vegetative growth and plant protection. Cucumber, melon and pepper plants were transplanted into coconut fiber containers with Si in the nutrient solution at 0.6 mM (+Si) and without Si (-Si) under optimal fertigation (OF) and moderate deficit fertigation (DF) conditions. Absorption of water, nitrate and potassium, vegetative growth, leaf firmness, loss of water through cuticle transpiration, cuticle thickness, number of trichomes and Si content in the epidermis and trichomes were measured. Trichome numbers, cuticle thickness and Si content were examined using light and SEM microscopes equipped for X-ray microanalysis. Resistance to two pathogens, Botrytis cinerea and Erysiphe cichoracearum, was also measured. The results show a loss of growth in the three cv. under DF that was alleviated when Si was supplied in the nutrient solution. +Si significantly improved water absorption and decreased leaf loss, which may explain the improvement shown in the growth parameters. +Si showed clear and significant growth increases in both the epidermis and the cuticle, which could justify both the observed greater resistance to diseases and the lower rates of water loss from the leaves. The three cv. showed high concentrations of Si in the trichomes, even under -Si treatments with a mean Si concentration lower than that in the +Si treatments.