Postillumination Respiration of Maize in Relation to Oxygen Concentration and Glycolic Acid Metabolism

Abstract

Prior illumination in C02-free air enhances a respiration from maize (Zea mays L.) leaves different in onset and duration from the postillumination burst of photorespiration. Respiration of attached leaves during the dark-light-dark sequence of the experiment was measured by infrared gas analysis of CO2 efflux from leaves at 25 ± 1 C into CO2-free N2 containing 0.04%, 2.23%, or 40% 02, or into C02-free air in an acrylic plastic chamber. Rapid flushing at 10 1 min-' replaced air by other gas mixtures.Respiration of excised leaves was measured as outlined above except for the following changes. Leaves were excised from the plant and recut beneath air-free distilled H20 in a beaker resting on the pan of a balance. The leaf was sealed into the chamber with the cut end of the leaf suspended in the beaker so that movement of solution into the leaf could be continuously monitored. In leaf-feeding experiments, the rates of respiration and steady transpiration were first established with the leaf in distilled H20, and before illumination the H20 was quickly replaced with 50 mm solutions of metabolites or with solutions containing the inhibitors HPMS1 or CMU. After illumination the pattern of respiration caused by each metabolite was then established using the protocol developed for attached leaves. During the respiration of some compounds. the 02 concentration was altered as previously described for attached leaves.The total volume of the heat exchange unit and chamber was 8.4 liters, giving a volume to leaf area ratio of approximately 20 cm2 cm-2. Relative humidity was 50 ± 5% during the experiments. Leaves were usually illuminated for 20 min at 0.38 cal cm-2 min-' (400-700 nm) during the dark-light-dark sequence to provide energy to stimulate influx of solutions of metabolites and respiration in the subsequent dark period. To measure the response to light of CO2 efflux during the illumination, illumination was attenuated with successive layers of

Light-enhanced dark respiration in leaves, isolated cells and protoplasts of various types of C4 plants

“…The reduction of leaf respiration after a period of photosynthesis at 1% O 2 , as we recorded for all species examined (Fig. 1), is consistent with earlier observations for Z. mays recorded by Heichel (1970Heichel ( , 1972. The decrease in post-illumination respiration could result from the limitation of oxygen diffusion into the leaf cells from an atmosphere with low O 2 , which could diminish the activity of the alternative respiratory pathway (Ribas-Carbo et al, 1994) which is also present in C 4 leaf mitochondria (Gardeström and Edwards, 1983;Stewart et al, 1990).…”

“…The CO 2 requirement was not greater than endogenous fixation, while the substrate for respiration, produced in the light, required oxygen for subsequent oxidation in darkness. Unexpectedly, the photorespiratory intermediates (glycolate, glyoxalate or glycine) fed to Z. mays leaves, in which the photorespiration is apparently absent, also doubled or tripled the respiration rate in darkness (Heichel, 1972). Further studies of the effect of light or metabolites on respiration in C 4 plants, particularly in species other than Z. mays, have not been undertaken to date.…”

Pathways of Carbon Fixation in Green Plants

“…In plant species with well-developed bundle sheaths, glycolate oxidase activity is greater in these cells than in the mesophyll cells (54,55). Maize leaves oxidized glycolate supplied in darkness, but the rate of CO 2 production was not rapid in relation to rates of photorespiration in iJ~efficient photosynthetic species (145).…”

The Effect of DCMU (3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea) on Photosynthesis, Glycolate Excretion (‘Photorespiration’) and Amino Acid Metabolism in the Blue‐Green Alga Anacystis

“…Kylin el al. (1972), Heichel (1972) and Orr el at. (1976) have shown that the effect of DCMU on photosynthesis, growth and motility in photosynthetic organisms may vary with the concentration of DCVIU.…”

“…Kylin et al (1972) used diderent concentrations of DCMU to map different sites of photophosphorylation in Scenedesmus. Leaves of maize supplied with glycolic acid and treated with DCMU released more COî nto COj-frce atmosphere in bright light than did controls without DCMU fed with glycolic acid (Heichel 1972 al. (1976) showed that low concentrations of DCMU ( 10"^ M) reduced the motile/non-motile balance in Euglena populations.…”