Published online by Cambridge University Press: 22 September 2009
BOTANY AND DISTRIBUTION
Soyabean or soybean, Glycine max (L.) Merr. which also is synonymous with Glycine soja Sieb. & Zucc., Glycine hispida (Moench) Maxim. and Soja max (L.) Piper, belongs to the family Leguminosae, subfamily Papilionoideae, tribe Phaseoleae and genus Glycine Wild. The genus Glycine is divided into two subgenera: Glycine and Soja. While cultivated soyabean is in the subgenus Soja along with its annual wild relatives G. soja and G. gracilis, the subgenus Glycine contains nine wild perennial species (Juvik et al. 1985): G. argyrea Tindale, G. canescens F.J. Herm., G. clandestina Wendl., G. cyrtoloba Tindale, G. falcata Benth., G. latifolia (Benth.) Newell & Hymowitz, G. latrobeana (Meissn.) Benth., G. tabacina (Labill.) Benth. and G. tomentella Hayata. All of the nine perennial species are native to Australia with seven of them restricted to Australia.
The soyabean plant is an erect, bushy and hairy annual. It can grow to a height of 20–108 cm depending on the genotype and length of growing period before flowering because soyabeans are reproductively photosensitive. The time needed to attain maturity can range from 75 to 200 days and this period is of great importance in the adaptation of the crop to a particular latitude. All cultivars flower earlier when grown in environments with 14–16 hours of darkness (Purseglove 1977). Grey or tawny hairs are found on the stem, leaves, calyx and pods. Primitive cultivars tend to be prostrate and this is particularly so when plants are shaded. Improved soyabean varieties are generally determinate in growth.