Effects of Water-Strain on the Minimum Intercellular Space Carbon Dioxide Concentration Γ in Wheat Leaves

Abstract

IN a recent communication, Rees¹ reported that midday closure in the oil palm was associated with water-strain and correlated in extent with total evaporation. There was also a relation with air temperature showing striking stomatal closure between 30° and 35° C., strongly reminiscent of the results of Heath and Orchard² for the log Γ/leaf temperature relation in onion and coffee leaves and of those of Heath and Meidner³ for the stomatal aperture/leaf temperature relation in onion leaves closed at the tip. Rees concludes: “Although increasing leaf temperature may cause stomatal closure, it is clear that midday closure of stomata may also be influenced by water-strain …”. In work carried out with wheat leaves we found a relation between degree of water-strain and Γ (the minimum intercellular space carbon dioxide content²) which is very relevant to this conclusion.