Determination of the Rate of CO₂ Evolution by Green Leaves in Light

Abstract

Abstract. The rate of CO,, evolution in light by green leaves was determined by 2 methods in a closed system of gas analysis and by measuring the amount of CO, evolved in-to a CO., free air stream in an open system. All methods gave similar results under comparable oonditions.A light stimulated CO., evolution from green leaves was found in all the plant species studied except corn where there was no apparent CO., evolution in the light.The magnitude of CO., evolution in light was markedly dependent on air flow rate and light intensity. At high light intensity and high flow rate, the rate of CO., evolution from green leaves was 1.4 to 1.7 times greater than that in darkness.In the pas.

Effects of Temperature on Photosynthesis and CO2 Evolution in Light and Darkness by Green Leaves

“…It has been reported that the rates of CO2 evolution by green leaves in light are affected by both O, concentration (6, 9, 11, 14, 29) and light intensity (3,6,15, 17,18,27). Decker (3) has shown that the post-illumination CO., outburst from tobacco at 33.5' was 3 times as large as that at 17.50 and Zelitch (34) has also shown that CO., evolution in light increases with a temperature increase from 250 to 350.…”

“…Additional knowledge would be of interest since there is increasing evidence to in.dicate that in green 'leaves the processes leading to the evolution of CO., in light and in darkness mav be different (6,9,11,17,23 35-day old watermelon and eggplants were used. The closed and the open systems of gas analysis were the same as described previously ( 15,16). The closed system was used to study the magnitude of the post-illumination CO. outburst, the CO., compen'sation point, and the effect of CO) concen,tration on -the rate of apparent photosynthesis at various temperattures.…”

Photorespiratory Phenomena in Maize

“…Under these conditions, most methods for detecting photorespiration would indicate its absence, for they depend on the maintenance of an internal CO2 level significantly above zero. A low internal CO2 level could account for the nearly equimolar uptake of "4CO2 and 'CO., by maize exposed to low (atmospheric) CO2 levels (15,45). Under these conditions the diffusion of each CO2 species would be directly proportional to its atmospheric concentration if its internal concentration were essentially nil.…”

“…Its CO2 compensation concentration (F ) approaches zero at temperatures less than 30 C (28,29,42) and is unaffected by 02 concentration (7,10); it releases little or no CO2 to CO2-free air (8,30) or even to C02-free oxygen (48); it fails to exhibit a CO, burst upon darkening (6,10,42); its net photosynthetic rate is not stimulated by lowering the ambient 02 concentration from 21 to 2% (3,5,7,14,18); and it does not depress the specific radioactivity of 14C during photosynthetic CO2 fixation (15,45). The absence of these external photorespiratory indices can be interpreted in two ways: maize either lacks photorespiration altogether, or it recycles photorespiratory CO2 with considerable efficiency.…”

Physiological responses of an aspen-poplar hybrid to temperature and soil moisture treatments

“…There is evidence that weak illumination curtails the dark respiration process and simultaneously initiates light-dependent photorespiration (Fock and Egle 1966;Forrester, et al 1966;Poskuta 1968a;1968b;Poskuta, et al 1967;Tregunna, et al 1966). Carbon dioxide (Hew, et al 1969;Holmgren and Jarvis 1967) and oxy gen (Govindjee, et al 1963;Hoch, et al, 1963) measurements indicate that dark respiration exceeds photorespiration at low light intensities but that as light intensity increases photorespiration is accelerated and dark respiration de creases and eventually ceases. Jackson and Volk (1970) state that this observation is in accord with the concept that low light is sufficient to curtail dark respiration while the initiation of photorespiration reguires a higher light inten sity and is responsive to increasing rates of photosynthesis.…”