Birla Laboratory, The Royal Agri-Horticultural Society of India, Calcutta.
Ten species of popular flowering shrubs viz., (1) Hibiscus rosasinensis var. My Beauty, (2) H. syriacus var: Double Mauve, (3) Tabemaemontrana coronaria, (4) Jasminum sambac var. Khoya, (5) Ixora singaporensis, (6) Lantana camara var. Sanguinea, (7) Cestrum noctumum, (8) Galphimia gracilis, (9) Allamanda grandi-flora, and (10) Clerodendron macrosiphon were grown one in a 17 cm pot. When the branches attained a length of 5–7 cms B-Nine (N-dimethylamino succinamic acid) was applied as foliar spray in 10,000, 7,500 and 5,000 ppm. Application of B-Nine promoted the growth of shoots in both the species of Hibiscus. Treated plants of Tabernaemontana and Jasminum sambac showed inhibition of shoot length due to the treatments. Increase in the numner of flowers was recorded in Tabernaemontana but not in Jasminum sambac. Marked retardation of plant height was obtained in Ixora singaporensis and Lantana camara with all the concentrations of the growth retardant and flowering also improved in both the species depending on the concentration. B-Nine at 5,000 ppm caused maximum reduction in plant height (17.9 per cent) in Cestrum noctumum and 100 per cent increase in the number of flowers was noticed in the same species by 7,500 ppm as compared to the untreated plants. In Galphimia gracilis, 5,000 ppm was found to be the most effective concentration for inhibition of shoot growth, but 7,500 ppm showed marked improvement in flowering. Lowest concentration (5,000 ppm) of B-Nine was found more effective for growth inhibition and increased flowering in Allamanda grandiflora and Clerodendron macrosiphon.
