Diurnal and seasonal patterns of leaf gas exchange in bahiagrass (Paspalum notatum Flügge) growing in a subtropical climate

Abstract

AbstractThe objective of this study was to evaluate the seasonal and diurnal changes in leaf gas exchange in bahiagrass (Paspalum notatum) plants grown in an irrigated lawn. Carbon dioxide assimilation, transpiration, stomatal conductance, leaf temperature and leaf‐to‐air vapour pressure difference were measured during the daylight period from April 2003 to March 2004. The monitored environmental variables were photosynthetic photon flux density, air temperature, air relative humidity, photoperiod and sunshine rate. Factor and cluster analyses were used to select variables and to group months with similar physiological and meteorological characteristics, and three distinct periods were identified: (i) May to July: with low energetic availability, low leaf temperatures and low photosynthetic activity; (ii) September to January: with high energetic availability, high leaf temperatures and high photosynthetic activity; and (iii) April–March–August: a transient period with environmental and physiological characteristics showing intermediate values. The reduced plant development and growth during the winter season was in accordance to the lower photosynthetic activity recorded from June to August, this variable being a potential indicator of reduced phytomass production. The relationships between leaf gas exchange and seasonal growth are discussed.