A comparison of in vitro with in vivo flowering in bamboo: Bambusa arundinacea

Seedling explants of Bambusa arundinacea were cultured in a Murashige & Skoog (MS) based liquid medium, supplemented with sucrose (2%), coconut water (5%) and 6-benzylaminopurine (2.2 mu M). In 3-6 months about 70% of the cultures flowered. A comparison was made between in vitro and in vivo flowering. Though smaller in size, in vitro florets were morphologically comparable to the in vivo florets. Anthesis in in vivo flowering took place in the morning hours. It was more or less synchronized and was dependent on the atmospheric temperature and humidity. The lemma and palea opened to expose both androecium and gynoecium to the pollinating agent (wind). In in vitro flowering, some florets opened as in their in vivo counterparts, some did not open but the anthers protruded from the tip of the partially opened lemma and palea. Anthesis was not synchronized under in vitro conditions. Pollen fertility in in vivo and in vitro flowerings were approximately 93% and 31% respectively. Studies by scanning electron microscopy showed some discrepancies in the pollen wall development in vitro. The trifid stigmas of in vivo florets were highly feathery with many papillae and withered soon after pollination or within few hours. The stigmas of in vitro developed florets were smaller with fewer and stouter papillae. They remained turgid for relatively longer periods. Seed production in in vivo flowering was profuse whereas in in vitro flowering seeds were produced only when many florets opened at the same time, in the same culture vessel.