Associations Among Seed Weight, Seedling Emergence, and Planting Depth in Cicer Milkvetch1

Abstract

AbstractThere is a great need for forage legumes that can emerge from deep depths of planting in semiarid environments because deep depths provide a greater cushion against the fluctuating moisture conditions found near the soil surface. Therefore, the objectives of this study were to compare selected progenies of cicer milkvetch, Astragalus cicer L., with seed weights of 3.2, 3.6, 4.0, 4.4, 4.8, 5.2, and 5.6 g/1,000 seeds for seedling traits that might be related to emergence and for ability to emerge from 1.3, 2.5, and 3.8‐cm depths of planting in the field.Seedlings from the seven seed classes differed significantly for hypocotyl diameter, hypocotyl length, radicle length, total length, and dry weight when grown in a dark germinator for 7 days at 25/15 C. In a greenhouse study the seed classes differed significantly for cotyledon dry weight, but not for cotyledon area, when sampled at the earlyprimary leaf stage. In both studies the values for the various characters generally were greater for the highseed‐weight classes than for the low.Although there were large differences between dates of planting both within and between years for seedling emergence in the field, the trends were similar with the high‐seed‐weight classes giving the greatest average emergence. The greatest difference among seed classes occurred at the 3.8‐cm depth, where seedling emergence of the 5.6‐g class was about twice that of the 3.2‐g class. Seedling emergence was similar for the 1.3 and 2.5‐cm depths of planting and generally was much higher for these two depths than for the 3.8‐cm depth. Correlation coefficients between seed weight, the various seedling traits, and seedling emergence at the 3.8‐cm depth were generally significant except for those involving hypocotyl length.