Silicon fertilization enhances the drought tolerance of soybean by maintaining leaf thickness

Abstract

Background and aimsThere is still limited information about the role of silicon (Si) in effects of water deficit in soybean. The association among Si uptake, gas exchange responses, and physiological and anatomical aspects in soybean under water deficit should be studied.MethodsA randomized factorial scheme experiment was conducted in pots with and without Si application in low soluble Si soil as silicate. In the R5 phase, three levels of watering were applied: 100% (well-watered, or WW), 60% (WD60), and 40% (WD40) soil field capacity (FC). The chlorophyll a and b (chla, chlb), carotenoid levels, net CO2 assimilation rate (A), stomatal conductance (gs), electron transport rate (ETR), transpiration (E), leaf Si concentration, and above-ground dry biomass were evaluated. Si deposition and anatomical modifications in leaves were also evaluated by scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDX) and light microscopy.ResultsWater deficit reduced only on chla, chlb, carotene, A, gs, and E. Si fertilization increased only the values of A and the leaf Si concentration, and Si was distributed in the epidermal cells. The leaves, mesophyll, and abaxial epidermis were thinner with WD60 and WD40 than with WW without Si. No difference in leaf or mesophyll thickness was observed among WW, WD60, and WD40 with Si.ConclusionsSi fertilization maintained the leaf thickness of the leaves of soybean plants under moderate and severe water deficit but did not influence the physiological or gas exchange responses of the leaves or the dry biomass during grain filling and maturity.