South African Journal of Plant and Soil Instructions to Authors

Single maize plants (Zea mays L cv. SNK 2244) were grown in sand culture in polyethylene tubes (300 mm × 110 mm diam.) in a glasshouse. Apparent photosynthetic rate was determined at intervals during the growing period, using a portable photosynthesis system (LI 6000). Photosynthetic rate was measured for a 1600-mm2 area in the centre of the youngest fully expanded leaf. During each experimental period, photosynthetic rate was measured on the same leaf of the same plant for population densities of 2,7; 5,5 and 11 plants m-2 which were obtained by varying the spacing between the plants. Photosynthetic rate decreased as plant density increased. Even at high solar radiant flux densities, the photosynthetic rate decreased in proportion to the decrease in radiant flux density due to mutual shading of leaves. This indicates that in the absence of other components of inter-plant competition, radiant energy may be a limiting factor in the productivity of maize crops