Seasonal Changes in Carbohydrate Accumulation for Two Creeping Bentgrass Cultivars

Controlled‐environment studies suggest that turf quality decline of creeping bentgrass [Agrostis stolonifera var. palustris (Huds.) Farw.] under heat stress is associated with decreases in carbohydrate availability in plants. The study was designed to examine and compare seasonal changes of carbohydrate status and C allocation pattern for two creeping bentgrass cultivars, ‘Penncross’ and ‘L‐93’, that differ in heat tolerance under field conditions. The experiment was conducted from May to November in 1999 and 2000. Grasses were managed under putting green conditions with daily irrigation and mowing at a 4‐mm height. Turf quality of both cultivars declined from May and reached the lowest level in August and September, and recovered in October. The content of total nonstructural carbohydrates (TNC), sucrose, and fructans in shoots and roots exhibited a similar seasonal pattern as turf quality for both cultivars in both years. Reducing sugar content decreased during the summer, but did not recover in October, except in shoots of L‐93 in 2000. The decreases in carbohydrate content were more pronounced in roots than in shoots for both cultivars. Carbon allocation to roots also decreased during summer for Penncross. Cultivar differences in carbohydrate content were not consistent between fractions of carbohydrate and times of the year. The decline in carbohydrate availability, particularly in roots, and limited C allocation to roots during summer could contribute to quality decline under field conditions; however, cultivar variation in carbohydrate content was not related to the differences in turf quality decline between two cultivars.