Time of Determination and Variations within and between Plants in Leaf Shape of Soybean

Abstract

Experiments were carried out to elucidate the time at which the leaflet shape was determined during growth, and to evaluate the extent of variation of leaf shape within and between plants in soybean. Two cultivars, "Kitakomachi" (broad type) and "Isuzu" (narrow type) and one line "Toiku 187" (intermediate type) were used. Leaflet shape was represented by LSI (leaf shape index). Leaflets determined their shape at early stages of growth, when the length and width of the leaflets of the three genotypes reached 40-60% of their maximum size. Left and right leaflets of each leaf on the main stem had almost the same shape, but their LSI values were smaller than that of central leaflets in all three genotypes. LSI values from the bottom to the top on the main stem differed between genotypes. The extent of variation of the LSI between plants in Kitakomachi was the smallest among the three genotypes, while that in Isuzu was the biggest. A LSI value of 2.6 can be used as a criterion for classifying broad and narrow types of leaf shapes, but further investigations are necessary to clarify the behavior of the intermediate type.