Comparison of pods of the terminal raceme of rapeseed (Brassica campestris var. Yellow Sarson) and mustard (Brassica juncea) cultivars

Abstract

Rapeseed and mustard cultivars aro morphologically determinate but the growth of the raceme, which is a corymbose type, is indeterminate. On the raceme flower opening proceeds acropetally in a sequential manner with one or two flowers opening each day. Thus there is a considerable time lag between first and last flower opening within the same raceme. In these oil-seed crops, besides leaves both pod wall and stems are photosynthetically active and the share of assimilates contributed by these three organs to the growing seeds has been estimated to be 37, 32 and 31%, respectively (Brar & Thies, 1977). A rapid decline in leaf area during pod filling in rapeseed and mustard (Chauhan & Bhargava, 1984) and rape (Allen & Morgan, 1972) cultivars has been observed. The assimilate supply to the pods developing at different periods may, therefore, differ owing to a decline in the leaf source as well as increasing intornal competition between pods. In winter oil-seed rape (Brassica napus), both mutual competition for assimilates and shading resulting from excessive pod production have been reported to cause heavy seed and pod losses (Mendham, Shipway & Scott, 1981). No information is available for rapeseed and mustard cultivars on how different components of the pod, such as its weight, seed weight, number of seeds and seed oil percentage, change according to their position on the terminal raceme. This information may be useful in deciding the appropriate number of pods on a raceme for optimum yield.