Stimulation of the Growth of Excised Cultured Roots of Soya Bean by Abscisic Acid

Excised root cultures of soya bean cultured at 30 °C in White's medium (1943) supplemented with 0⋅1 per cent yeast extract have been serially sub-cultured over 13 culture passages of 7 days although a decline in the linear growth and lateral formation begins in the third passage and the roots are devoid of laterals from the 8th passage onwards. Applications of abscisic acid within the concentration range 0⋅01–0⋅001 mg l−1 and during the first two culture passages enhanced the linear growth of the main axis, the number of emergent laterals and the total length of laterals. This effect has been shown for two cultivars, with roots derived from seed in both its first and second year of storage and under different conditions of culture and culture pH.