Effects of Acute Moisture Stress on Creeping Bentgrass Cuticle Morphology and Associated Effects on Foliar Nitrogen Uptake

Abstract

Foliar fertilization is a common practice to deliver nitrogen (N) to turfgrasses. The mechanisms of foliar applied nutrient uptake, particularly the effects of the leaf cuticle layer, have not been clearly characterized in turfgrasses. The objectives of this study were to determine the effect of acute moisture stress on the morphological and compositional components of the cuticle and the resulting effect on foliar-applied N absorption. Creeping bentgrass (Agrostis stolonifera L.) was irrigated to return 100% or 50% evapotranspiration rate (ET) for 10 days to examine cuticular modifications resulting from acute moisture stress and foliar N uptake with and without a surfactant. Acute water stress increased the total cuticle wax by 11%, mostly as a result of the compound 1-hexacosanol, and increased crystalloid density creating a rougher leaf surface. The 50% ET treatment significantly reduced recovery of 15N-labeled urea by 14%, which was attributed to the increased total cuticle wax and crystalloid density making the surface less receptive to foliar applications. The surfactant addition to the urea solution increased 15N-labeled urea recovery by 21% and absorption of 15N in 50% ET plants to levels consistent with the 100% ET plants. These results suggest that acute moisture stress modifies the cuticle wax load and morphology, thereby hindering foliar absorption; however, a surfactant addition can help to mitigate this effect and increase absorption of N.