Seasonal Fluctuations in Growth/Decline and Single-Leaf Gas Exchange of C3Turfgrass Fields Under Various Light Conditions

Abstract

Seasonal variation in non-assimilatory organ and leaf biomass and necromass, leaf area index (LAI), leaf mass per unit area (LMA), and leaf nitrogen content per unit leaf area of managed C3cool-season turfgrass (Kentucky bluegrass, Poa pratensis L.) fields under four light conditions (irradiance levels: 100, 62, 48, 20%) were examined in situ over 2 years. Seasonal fluctuations in light and the temperature dependence of the gas exchange of intact leaves grown under three light conditions (irradiance levels: 100, 48, 20%) were also examined for 1 year. The magnitude of spring growth and summer decline in non-assimilatory organ and leaf biomass depended on the light conditions. Both non-assimilatory organ and leaf biomass were higher in the sunnier plots, as was the ratio of non-assimilatory organs to whole biomass. A step wise acclimatization to low irradiance reduced the allocation to non-assimilatory organs to maintain leaf biomass, limited LMA to maintain the LAI, and limited the latter to retain leaf nitrogen per unit leaf area, depending on the shade level. Kentucky bluegrass growing under lower light conditions had similar single-leaf photosynthetic abilities until early summer, but the normalized maximum carboxylation rate at 25°C [Vcmax25] decreased during the decline of turfgrass in summer, depending on the shade level, which corresponded to the decline in leaf nitrogen content per unit leaf area. © 2011, The Society of Agricultural Meteorology of Japan. All rights reserved.