SHOOT PHYSIOLOGICAL-RESPONSES OF 2 BENTGRASS CULTIVARS TO HIGH-TEMPERATURE AND POOR SOIL AERATION

Understanding the effects of high temperature and poor soil aeration a nd their interaction on growth and physiology of creeping bent-grass ( Agrostis palustris Huds,) will help management and breeding programs t o improve summer turf quality. The objective of this study was designe d to examine shoot physiological responses of 'Crenshaw' and 'Penncros s' 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 w ere (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 d rained 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, chloroph yll content (Chl), and net photosynthetic rate (P-n) declined with inc reasing temperatures or declining aeration for both Crenshaw and Pennc ross, The HT treatment increased canopy minus air temperatures (Delta T) and dark respiration rates (R-n) for both cultivars, crith a greate r rise in R-n for Penncross (44%) than for Crenshaw (25%), The LA trea tment inhibited R-n but had no effect on Delta T. The combination of H T and LA had more severe adverse effects than either HT or LA alone on turf quality, leaf chlorophyll content, photosynthesis, and respirati on, particularly for Penncross. The results demonstrated genetic varia tions in shoot physiological responses to high temperature and poor so il aeration stresses in creeping bentgrass and indicated that high tem perature, when combined with poor soil aeration lead to turf quality d ecline. This was mainly due to reduced net photosynthesis and increase d respiration rates.