No abstract

The CO. exchange of shoots of Trifolium repens, Fragaria chiloensis x virginiana, Celmisia spectabilis, Lycopersicum escllientum, Lolium perenne, and Chionochloa rubra were determined at exposed leaf temperatures of 4' to 55°c and five light intensities. The maximum rates of exchange for the first three species at a photosynthetic irradiance of 340W.m-2 were 58, 23, and 5 mg C02.g-1 .hr-1 respectively, and for the remaining species at 270 W.m-2 were 45, 49, and 4 mg CO •. g-l.hr-1 respectively. CO, release in the dark increased 5-to IO-fold over the range 2"-30•c. At high light intensities Celmisia spectabilis and Chionochloa rubra had their maximum rates of uptake at the lowest temperatures. The other four species had their maximum rate of uptake in the 20°_35°c exposed-leaf temperature range, the rate decreasing rapidly to a net release in the 40'-50'c range.

No abstract

THE ABILITY OF PLANTS to capture light energy is the key to the continual survival of all life. Light absorbed by the green parts of plants is used to fix carbon dioxide from the air and convert it into energy-rich compounds which are then translocated to other parts of the plants. There they may be stored or used to provide energy for growth processes with consequent release of carbon dioxide. This energy from sunlight which is stored in biochemical compounds is the only source of energy for growth and is only a small portion of the total incident sunlight. The rate at which plants can take up carbon dioxide is thus a good measure of the rate at which plants absorb useful energy. However, in practice, only the net exchange of carbon dioxide which results from the uptake by photosynthesis and release by respiration can be measured.