Effects of age, washing and temperature on the germination of immature seeds, the growth of the radicle, and the time to flowering, in soybean.

The effects of seed age, washing time and temperature on the precocious germination, radicle growth and time to flowering of immature soybean seeds [Glycine max (L.) Merr.] cv. Williams, were studied. Seeds of 25, 30, 35 and 40 days after antesis (DAA) were used. Washing was done with distilled aerated water, during: 0, 12, 24 and 48 h, at 20, 25, 30 and 35°C. The germination of the seed was continued in Petri dishes, in the dark, at the same temperatures. A factorial design 4 x 4 x 4 (age x washing time x temperature) with two replicates of 20 seeds was used. A control of mature and dry seeds (> 60 DAA) was included. Both, germination percentage, and radicle growth rate increased with seed age. Washing stimulated germination and early post-germinative events independently of the washing time. Temperatures of 20 and 30 °C did not change neither germination rate nor radicle growth rate, but both parameters dropped abruptly at 35°C. This temperature also inhibited seedling survival of 25 and 30 DDA seeds. After 35 DAA the survival of seedlings became temperature independent. Days to flower increased inversely to the age of the seeds. Washing shortened the time to flowering in plants produced by immatured seeds. Temperatures betweeen 20 to 30°C during germination did not have an effect on flowering time.