Indian Journal of Plant Physiology

The differential germination and flowering behaviour of tuberose (Polianthes tuberosa L.) bulbs of different sizes were analysed. The bulbs were categorised on the basis of their size, weight, respiratory rate, soluble and insoluble carbohydrates amylase activity and gibberellin content. The amylase activity was highest in category III (small) bulbs whereas gibberellin content and soluble carbohydrates were highest in category I (big) bulbs. Soluble carbohydrates in the apical region of the bulbs always remained high compared to basalplate and scale leaves in all categories of bulbs. Higher metabolic activity was restricted to the apical region of the smaller bulbs whereas the metabolic activity in the larger bulbs was lower in apical and higher in basalplate and scales.

Pretreatment of bulbs with GA₃, kinetin and ABA showed that GA₃ had no effect while kinetin and ABA had pronounced promotive effects on germination. ABA was most effective in promoting germination of smaller bulbs. Here GA₃ and kinetin completely inhibited flowering. ABA promoted flowering in all categories of bulbs but more remarkably in the larger bulbs. The possible reasons for differential bshaviour in germination and flowering of different categories of bulbs have been discussed.