Relationship between Photosynthesis and Respiration

Abstract

The rate of dark CO2 efflux from mature wheat (Triium aestivum cv Gabo) leaves at the end of the night is less than that found after a period of photosynthesis. After photosynthesis, the dark CO2 efflux shows complex dependence on time and temperature. For about 30 minutes after darkening, CO2 efflux includes a large component which can be abolished by transferring Muminated leaves to 3% 0 and 330 microbar CO2 before darkening. After 30 minutes of darkness, a relatively steady rate of CO2 efflux was obtained. The temperature dependence of steady-state dark CO2 efflux at the end of the night differs from that after a period of photosynthesis. The higher rate of dark CO2 effiux followin photosynthesis is correlated with accumulated net CO2 assimilation and with an increase in several carbohydrate fractions in the leaf. It is also correlated with an increase in the CO2 co_msation point in 21% 02, and an increase in the light compensation point. The interactions between CO2 efflux from carbohydrate oxidation and photorespiration are discussed. It is concluded that the rate of CO2 efflux by respiration Is comparable in darkened and illuminated wheat leaves.The rate of CO2 efflux by respiration from single leaves and whole plants in the dark is linearly related to the rate of previous photosynthesis when the latter is varied by changing the light level or CO2 concentration (18,21). McCree (21) fitted an empirical equation in which the rate of dark CO2 efflux is proportional to photosynthesis and dry weight of living material on the plant. This served as a basis for development of the theoretical concepts of growth and maintenance respiration by Penning de Vries (24). Both of these components of respiration are thought to involve, principally, carbohydrate oxidation through glycolysis, the pentose phosphate pathway and the tricarboxylic acid cycle. Growth respiration appears to be less sensitive to temperature than maintenance respiration (22). Explanations of the complex interactions between photosynthesis, temperature, and dark respiration are uncertain, although it is probable that the interaction is mediated by carbohydrate level (6,8).The extent to which tricarboxylic acid cycle respiration continues in the light in green leaves is uncertain. Graham (12) concluded that biochemical evidence suggests the tricarboxylic acid cycle continues to operate in illuminated leaves at about the same rate as it does in darkness. Physiological evidence is contradictory; some experiments are best explained in terms of significant CO2 efflux in illuminated leaves from sources other than photorespiration (3, 12) whereas others suggest that these other sources are negligible (7, 19, 23). The lack of methods for direct measurement ofthe rate ofrespiration during photosynthesis greatly complicates the resolution of this question. A new experimental approach is attempted in this paper.The experiments described here investigate the relationship between photosynthesis in mature wheat leaves, its products (particularly carbohyd...

Alterations in Growth, Photosynthesis, and Respiration in a Starchless Mutant of Arabidopsis thaliana (L.) Deficient in Chloroplast Phosphoglucomutase Activity

“…An analogous effect, observed in wild-type plants of some other species (3), has been interpreted as evidence that the amount of respiration is responsive to the amount or form of storage carbohydrate (3). Because the starchless mutant accumulates high levels of soluble carbohydrate in the light which rapidly decline in the dark, it seems likely that, as suggested (2,3,6), the amount of respiration is proportional to the availability of substrate rather than to the demand for ATP and NADH. It remains to be seen if the abnormally high respiration of the mutant is due to alternative oxidase activity which has been invoked to explain substrate-regulation of respiration (3,15,29).…”

“…The effect of carbohydrate accumulation on the rate of dark respiration has received less attention but appears to have been consistently observed by a variety of approaches (2,6,29). The essential observation is that the rate of respiration is proportional to carbohydrate content or is stimulated by provision of exogenous carbohydrate.…”

Leaf Photosynthesis and Respiration of High CO2-Grown Tobacco Plants Selected for Survival under CO2 Compensation Point Conditions

“…The fact that these plants were grown at high CO2 undoubtedly facilitated carbon accumulation and, perhaps, exaggerated possible genotypic differences in this character. The rate of respiration ofleaves in the dark may depend on the carbohydrate content, as shown in several species (2,5,6,8,16), and this dependence may have varied in the selected tobacco lines. The leaf respiration of selected SP lines was apparently less sensitive to carbon content, allowing a greater carbon accumulation per unit area and, perhaps, more efficient carbon storage for subsequent use in growth.…”

Metabolic regulation of leaf respiration and alternative pathway activity in response to phosphate supply

“…Respiratory activity is often correlated with carbohydrate levels (Penning de Wries, Witlage & Kremer 1979;Azcón-Bieto & Osmond 1983;Farrar 1985;Amthor 1994;Felitti & Gonzalez 1998). It has been suggested that at high carbohydrate levels there could be more alternative pathway activity if excess substrate saturates the cytochrome pathway Lambers 1997).…”