Physiological responses of Cynodon dactylon Pers. and Stenotaphrum secundatum (Walt.) Kuntze to chilling temperatures as affected by gibberellic acid

Abstract

Low temperature discoloration of warm season turfgrasses occurs with the advent of cool fall temperatures above 0 C but below 10 to 12 C. Total loss of the pigment system and subsequent death of the leaves and stems of the turfgrass plant is the result of physiological disruptions referred to as chilling injury. The objectives of this investigation were to (1 ) describe the visual symptoms of chilling injury, (2 ) observe chloroplast ultrastructure, and (3) monitor carbon dioxide fluxes in chilling resistant and chilling sensitive cultivars of both bermudagrass (Cynodon dactylon Pers.) and St. Augustinegrass (Stenotaphrum secundatum (Walt.) Kuntze), while exposed to chilling temperatures and as affected by gibberellic acid. Ormond (chill tolerant) and Pee Dee (chill sensitive) were the two bermudagrass cultivars used. The two St. Augustinegrass cultivars used were Floratam (chill tolerant) and Texas Common (chill sensitive). Bleaching and/or the formation of a purple pigmentation occurred in the leaf blades and stems of both bermudagrass cultivars within 3 days of chilling stress. The symptoms occurred first and proceeded more rapidly on Pee Dee bermudagrass. Both St. Augustinegrass cultivars showed visual symptoms after 5 or more days of chilling stress. Wilting was the first visual symptom apparent on both cultivars..