The increase in the ratio of leaf area to leaf weight which occurs with shading of legumes was associated with changes in leaf morphology and chlorophyll content. Alfalfa and birdsfoot trefoil had more stomata per cm2 of leaf when grown in the sun than in the shade. Sun leaves of both species were thicker than shade leaves. Number of palisade and mesophyll cells and cell volume appeared greatest in sun leaves, and the palisade layer was more clearly differentiated. Shaded leaves contained more chlorophyll per unit of leaf weight but less per unit of leaf area than sun leaves.
Seedling gowth of four blrdsfoot trefoil, (Lotus corniculatus L.) varieties, ‘Empire,’ ‘Tana,’ ‘Viking,’ and ‘Leo’ was evaluated during the non‐photosynthetlc stage of development for speed of germination and elongation, rate of emergence and rate of respiration. The speed of germination, elongation, and emergence speed of Leo was significantly greater than for other varieties. This was not due to differences in imbibition rate, nor was it related to respiration rate. Varieties ranked in the same order for all measurements but respiration. Rank order was Leo > Tana > Viking > Empire. A similar order of rank in yield was found when these varieties were grow in growth chambers or in the field. Respiration rates were similar for all varieties within each of six age groups and each of three growth temperatures. Respiration rates increased significantly for all varieties with increasing temperature.
Seedling vigor of four birdsfoot trefoil varieties was studied in growth chambers, at two temperatures, 21 and 27 C. Vigor was evaluated in terms of relative growth rate and its components, net assimilation rate and leaf area ratio. At 21C, relative growth rate of Leo was superior to other varieties and relative growth rate of ‘Tana’ and ‘Viking’ was superior to ‘Empire’. The superiority of ‘Leo’ over Tana and Viking was attributed to a greater leaf area ratio but the superiority of Leo over Empire was due to a greater net assimilation rate. The greater superiority of Tana and Viking over Empire was due to a greater net assimilation rate.At 27C, relative growth rate of Leo and Tana was greater than relative growth rate of Empire. The difference was due to a greater leaf area ratio since net assimilation rate of all varieties was the same. Within a temperature, differences in leaf area ratio between varieties were associated with changes in the leaf area to leaf weight ratio since the ratio of leaf weight to plant weight was the same.With increasing temperature, leaf area ratio decreased as a result of a decrease in the ratio of leaf weight to plant weight. The other component of LAR (the leaf area to leaf weight ratio) increased with increasing temperature, but not enough to counteract the effect of the decrease in the ratio of leaf weight to plant weight. The decrease in leaf area ratio with increasing temperature was not great enough to affect relative growth rate. Both relative growth rate and net assimilation rate at the two temperatures were the same.
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