Net photosynthetic rate in peanut (Arachis hypogaea): Influence of leaf position, time of day, and reproductive sink

Net photosynthetic rate (PN) was studied in field-grown peanut cv. GG 2 in relation to leaf position, time of day, reproductive-sink, and phenophase. In general, PN remained higher in the upper leaves than in the lower leaves. The mean PN of the leaves situated upper and the leaves lower in the canopy increased fom the morning, reached a maximum during noon hours, and decreased thereafter. Between 09:00 to 10:00 h, PN, stomatal conductance (gs), and transpiration rate (E) in the upper leaves were higher than in the lower leaves, but between 12:00 and 13:00 h, these activities increased significantly in the lower leaves. Highest PN was found during pod-development phase. The PN per unit leaf area in plants with reproductive-sink (WRS) was similar to those without reproductive-sink (WORS). However, leaf area of WORS plants decreased significantly, mainly due to the reduction in number of leaves.