Leaf Trimming and High Temperature Regulation of Phytohormones and Polyamines in Creeping Bentgrass Leaves

Abstract

Mowing frequencies are associated with differences in disease susceptibility of turfgrasses, but how hormones respond to mowing practices are not fully understood. Two independent growth chamber experiments were conducted to determine how leaf trimming and heat stress play a role in modulating endogenous hormones within creeping bentgrass (Agrostis stolonifera) leaf tissues. The study also aimed to evaluate whether there are hormone changes at 0, 15, and 30 minutes after leaf trimming (wounding). The effects of trimming and temperature on sod plugs of creeping bentgrass ‘Penncross’ and ‘Penn-G2’ were investigated under optimal conditions (23/20 °C day/night) and heat stress (30/25 °C day/night). Plants were 1) untrimmed and sampled by plucking at the leaf base, 2) untrimmed and sampled by cutting at 0, 15, and 30 minutes, or 3) trimmed once every 3 days. Salicylic acid (SA), jasmonic acid (JA), abscisic acid (ABA), and indole-3-acetic acid (IAA) were generally greater in untrimmed plants compared with plants trimmed every 3 days under high temperature conditions. Zeatin riboside (ZR) was lower in untrimmed plants compared with plants trimmed every 3 days. JA and gibberellic acid (GA) accumulated to greater levels in the plants after 15 and 30 minutes of sampling. Polyamines (PAs) exhibited a transient increase in putrescine (Put) due to wounding. The results demonstrate the importance of research practices that consider the timing of sampling turfgrass plants for hormone analysis, help elucidate why mowing practices may play a role in stress susceptibility, and may be applicable to various studies related to leaf wounding.