Crop photosynthesis, respiration and dry matter production of maize.

Abstract

Aboveground net photosynthesis and respiration of maize cv. LG11 was determined in the field between mid-June and end-Oct. at regular intervals (1-2 weeks) at 12.5 and 22.5 degrees C by measuring the CO₂ uptake or release in mobile crop enclosures. The actual growth rate of the crop was determined from fortnightly harvests. Temp. dependence of photosynthesis was highest in the early (until mid-July) and very late (early Oct.) stages of crop growth, showing a reduction of about 50% at the higher irradiances (>400 W/msuperscript 2). In the period of major DM production (mid-July to Sep.) the reduction was only 12-15%. Assuming maintenance respiration to become constant for cobs and grain exceeding a yield of 1000 kg/ha and for stems exceeding 2500 kg/ha, the measured and calculated dark respiration at 22.5 degrees matched fairly well. At 12.5 degrees the calculation, using the same assumptions, significantly overestimated dark respiration during the first part of the growing period. The carbon balance sheet showed that from the total amount of CO₂ absorbed by the crop (equivalent to 30.7 t DM/ha), 30% was lost by aboveground respiration and 50% was invested in aboveground harvestable material. The remaining 20% was assumed to be transported to plant parts below ground. Substantial losses of DM at the end of the growing season did not occur. (Abstract retrieved from CAB Abstracts by CABI’s permission)