Metabolic Changes During Cold Acclimation and Deacclimation in Five Bermudagrass Varieties: II. Cytokinin and Abscisic Acid Metabolism

Abstract

ABSTRACTBermudagrasses (Cynodon spp.) grown in the U.S. transition zone and other regions with a similar climate undergo cold acclimation in fall and deacclimation in spring. Physiological mechanisms of cold acclimation and deacclimation associated with freezing tolerance and spring green‐up are not well documented. This study investigated changes in cytokinin (t‐zeatin riboside [t‐ZR]) and abscisic acid (ABA) during cold acclimation and deacclimation in five bermudagrass entries in growth chambers. One ecotype (GA‐851) and four cultivars (Patriot, Riviera, Tifway, and Princess‐77) were subjected to cold acclimation at 8/4°C (day/night) for 28 d and then deacclimation at 10/5, 21/7, 23/8, and 26/14°C for either 3 wk (standard deacclimation) or 1 wk (fast deacclimation treatment). Stolon t‐ZR content declined while ABA content increased during cold acclimation. Patriot and Riviera had higher levels of stolon ABA relative to Princess‐77 at the end of cold acclimation. During deacclimation, t‐ZR increased as the temperature increased to 26/14°C, while ABA declined as the temperature increased from 10/5 to 21/7°C. Patriot, GA‐851, and Tifway had higher levels of t‐ZR relative to Riviera and Princess‐77. Abscisic acid level during cold acclimation may be associated with freezing tolerance, while cytokinin level during deacclimation may be associated with rate of spring green‐up of bermudagrass. The results suggest that selection and use of entries with higher levels of ABA during cold acclimation and cytokinin during deacclimation could improve bermudagrass winter survival and spring green‐up in transition zone climates.