Effect of seed size on the germination of velvet bean seeds.

Abstract

The velvet bean Mucuna aterrima [(Piper et Tracy) Holland] is a legume used as green manure and for animal feeding. Its seeds usually show dormancy, caused by the impermeability of the seed coat to water. One of the factors which could interfere on the dormancy degree is seed size, but there is not complete agreement among seed researchers about this matter. The aim of this work was to study seed size effect on the physiological quality of velvet bean seeds. Racemes of senescent plants were harvested when the legumes were dry and some of them were in dehiscence. After the manual thrash of the legumes, the seeds were packed in paper bag and stored under natural conditions in a laboratory, by six months. The seeds were sized for thickness by using oblong screen holes of 8 x ¾”, 6 x ¾” and 2 x ¾”; following, the seeds of each one of these three thickness grades were sized for width by using screens of round holes of 26, 24, 22 and 20. Seeds of six sizes (8 x ¾ - 26, 6 x ¾- 26, 2 x ¾ - 26, 6 x ¾- 24, 2 x ¾ - 24 and 2 x ¾- 22) were thus obtained. These sizes were submitted to germination test to evaluate the percentages of normal seedlings, abnormal seedlings, hard seeds and dead seeds. The seeds of small size grades showed higher hard seeds percentage but higher germination potential than those of larger sizes.Additional keywords: Mucuna aterrima; legume; dormancy.