Night Respiration of a Maize Crop in the Lowland Humid Tropics

Abstract

(1) High night temperatures (minimum temperature in range 22-25 $^\circ$C), could contribute to the lower yields of maize crops grown in the humid tropics compared with temperate areas because of higher rates of respiration. (2) Overnight respiration losses of whole plants were measured in a young maize crop grown in the humid tropic zone of Western Nigera. In an older crop, overnight leaf respiration was measured. (3) In the younger plants, respiration rates initially were high (c. 15% overnight reduction in dusk plant dry weight) but they declined to c. 5% by 27 days after emergence (d.a.e.). Overnight leaf respiration caused 4% reduction in dusk lamina dry weight. Nightly dry weight losses by whole plants averaged 40% of daily dry weight gain. (4) Assuming a value of 12 mg g$^{-1}$ per 12 h with a Q$_{10}$ of 2 for the maintenance component of respiration for the period 11 to 27 d.a.e., overnight dry weight loss could be reduced to 37% and 35% of daily gain for a 10 $^\circ$C and 20 $^\circ$C decrease in night minimum temperature. Such dry weight conservation, if maintained through the remaining period of crop growth could give yield increases of 200 and 300 kg ha$^{-1}$ respectively, and at best. c. 5% improvement on Experimental Station yields of elite varieties. (5) On this basis it appears that high night temperatures are of minor importance in explaining yield differences between the humid tropics and temperate zones.