Elongation Force of Seedlings of Leguminous Crops1

Abstract

Using an unbonded strain gauge transducer and a null balancing recorder, the vertical elongation or lifting forces of 3‐ and 5‐cm tall seedlings of 12 leguminous species grown in darkness at about 23 C were measured. The elongation force (El) gradually increased after initially setting the cotyledons of hypogeous seedlings or plumular hooks of epigeous seedlings against the receptor of the transducer. The maximum force was reached 20 to 50 hours after the initial setting, with a gradual decrease thereafter.The maximum Ef differed significantly among species and among cultivars within species. The mean value for the maximum Ef of a species was positively correlated with seed weight (0.787** in 3 cm, and 0.816** in 5 cm tall seedlings). Furthermore, in seedlings 3 cm tall, highly positive relationships were found between stem area at the center portion‐of the seedling and seed weight (0.787**) or the mean value for the maximum Ef of a species (0.971**). The results indicate that the large seeded species produce large stems and therefore a large Ef.The maximum Ef per unit mass of seed was smaller in species which produced an epicotyl such as broad bean (Vicia faba L.), pea (Pisum sativum L.), and azuki bean (Phaseolus radiatus L. vat. aurea Prain.) compared to species which produced a hypocotyl such as peanut (Arachis hypogaea L.) and soybean (Glycine max (L.) Merrill). Among species which produce a hypocotyl, the elongation force was less in soybean and sword bean (Canavalia gradiata DC.) than in other species tested.