Foliar application of sodium silicate mitigates drought stressed leaf structure in corn (Zea mays L.)

Abstract

A hydroponic study of maize cv. SC 705 was performed to determine the effectiveness of 1.0 mM sodium silicate to alleviate drought stress. Measurements were taken between 5 and 100 mm above the base of the third leaf. Stress negatively affected all growth parameters. As a general trend, a 1.0 mM Na2SiO3 foliar application increased growth parameters for stressed, but not un-stressed plants, compared to the control. Leaf cross sectional area increased 35%, and midrib area decreased 25% less than in untreated stressed plants, compared to the control. Protoxylem area in treated, drought-stressed plants increased by 40%, and Si application increased xylem in non-stressed plants compared to the control. In drought stressed seedlings the stomatal area increased 24% when Si treated compared to the control. In drought stressed plants, electrolytic leakage decreased from 0.64 to 0.52% when Si treated. Membrane stability increased 12% in drought stressed plants when Si treated. When drought stressed plants were Si treated, chlorophyll a increased by 35%, chlorophyll b increased by 31%, and carotenoids increased by 51% compared to the control. Drought stressed plants had a relative water content 15% higher than non-treated plants, and leaf elongation rate increased 33%, compared to the control. Compared to the control, drought stressed plants had a 20% higher K+ and 38% higher Ca2+ level when treated with Si. These data strongly support the hypothesis that foliar Si application could mitigate the effects of drought stress. Growth improvements could be correlated with increased K+ and Ca2+ accumulation, which may play an important role in increased midrib cross-sectional area, RWC, and third-leaf elongation under drought stress. Foliar application of Si could be a low cost, easy, and effective way to improve seedling establishment in corn affected by drought early in the season.