Shoot physiological responses of two bentgrass cultivars to high temperature and poor soil aeration

Understanding the effects of high temperature and poor soil aeration and their interaction on growth and physiology of creeping bent-grass (Agrostis palustris Huds,) will help management and breeding programs to improve summer turf quality. The objective of this study was designed to examine shoot physiological responses of 'Crenshaw' and 'Penncross' to high temperature and poor soil aeration, Turf was maintained in growth chambers at day/night temperatures of 22/15 degrees C (optimum) or 35/25 degrees C thigh temperature, HT), Soil aeration treatments were (i) adequate aeration with oxygen diffusion rate (ODR) at 1.5 mu g cm(-2) min(-1) by maintaining the soil medium well watered and well drained and (ii) low aeration (LA) with ODR below 0.2 mu g cm(-2) min(-1) induced by flooding the soil medium. Turf growth, quality, chlorophyll content (Chl), and net photosynthetic rate (P-n) declined with increasing temperatures or declining aeration for both Crenshaw and Penncross, The HT treatment increased canopy minus air temperatures (Delta T) and dark respiration rates (R-n) for both cultivars, crith a greater rise in R-n for Penncross (44%) than for Crenshaw (25%), The LA treatment inhibited R-n but had no effect on Delta T. The combination of HT and LA had more severe adverse effects than either HT or LA alone on turf quality, leaf chlorophyll content, photosynthesis, and respiration, particularly for Penncross. The results demonstrated genetic variations in shoot physiological responses to high temperature and poor soil aeration stresses in creeping bentgrass and indicated that high temperature, when combined with poor soil aeration lead to turf quality decline. This was mainly due to reduced net photosynthesis and increased respiration rates.