Plant form, growth rate and relative growth rate compared in conventional, semi-leafless and leafless peas

Abstract

Measurements of internode length, of leaf size and dry weight, of stipule size and dry weight, of stem dry weight and of seed yield were obtained from near-isogenic stocks of leafless, semi-leafless and conventional peas. The form of the semi-leafless pea was similar to that of the conventional pea but that of the leafless plant differed considerably. In comparison with conventional peas, leafless peas had shorter vegetative internodes, longer reproductive internodes and heavier stipules and leaflets at the reproductive nodes. They yielded less seed but had a higher harvest index. Relative growth rates over a period of 19–48 days after sowing were estimated in the 3 types of near-isogenic pea and also, over a period of 15–47 days after sowing, in 5 conventional pea cultivars and 5 experimental leafless accessions. The relative growth rate of the near-isogenic leafless plant was significantly less ( P = 0.05−0.01) than that of the conventional form, the reduction being principally due to a significant reduction ( P = 0.01−0.001) in relative growth rate of the stem. In the 5 conventional and 5 leafless peas there were no significant differences in growth rate of the whole plants, but significant reductions were again to be seen in the relative growth rate of the stems.