A physiological and mathematical study of the growth and productivity of a Cattuna-Sphagnum community. 1. Net photosynthesis of Cattuna vulgaris L. Hull.
Abstract
A description is given of apparatus used for measuring photosynthesis and respiration in C. vulgaris under controlled conditions of light intensity, r.h. and leaf temperature resembling those found in the field. Preliminary experiments indicated that net photosynthesis was only slightly dependent on temperature at high light intensities; the temperature optimum changed with increasing light intensity. Net photosynthesis was strongly influenced by previous temperature regime, particularly at high light intensities. Young shoots never became completely light saturated, but light saturation began sooner at lower temperatures; compensation points were notably high. Shoot age had relatively little effect on net photosynthesis but was very significantly related to dark respiration. The presence of flowers on individual plants was associated with a higher rate of shoot photosynthesis; removal of flowers caused the rate of gross photosynthesis to drop markedly over a period of 11 days. Seasonal increases in photosynthesis were accompanied by corresponding decreases in the sugar content of the shoots, but the relationship was not entirely consistent. -R.B.