Studies on Reproductive Development and Breeding Habit of the Commercially Important Bamboo Bambusa tulda Roxb

Compared to other grasses, flowering in bamboo is quite divergent, yet complex with respect to time to flower, number of individual culms in a population that have been induced at a time (sporadic vs. gregarious), nature of monocarpy, morphology of inflorescences (solitary spikelet vs. pseudospikelet), biology of pollen and nature of genetic compatibility. Wide diversity exists even across species and genotypes. However, due to the rarity of flowering and inaccessibility, few studies have been done to systematically analyse diverse aspects of the reproductive behaviour of bamboo. In this study, four recurrently occurring, sporadic flowering populations of Bambusa tulda have been closely observed over the last seven years. Detailed inflorescence and floral morphology and development of reproductive organs have been studied. Pollen viability was assessed by staining and in vitro germination. Self and cross pollination experiments were performed in a plantation site to assess the genetic nature of pollen-pistil interaction. The study identifies interesting reproductive features, that are not common in other grasses. A few important observations include the early appearance of a solitary spikelet vs. late appearance of a pseudospikelet in the flowering cycle, low rate of pollen germination, protandry, self-incompatibility and higher rate of seed setting by the pseudospikelet as compared to the solitary spikelet. The findings will not only be useful to understand the reproductive behaviour of this non-woody timber plant, but will also be useful for forest management and sustainable use of bamboo bioresources.

Development of inflorescences and flowers in Fabaceae subfamily Dialioideae: an evolutionary overview and complete ontogenetic series for Apuleia and Martiodendron

The goal of this study was to better understand the origin and development of flowers and inflorescences in the newly established subfamily Dialioideae, an unusual and morphologically variable clade of Fabaceae due to its varied levels of floral reduction. We present here the complete ontogenetic series for two species characterizing different levels of floral reduction: Apuleia leiocarpa, an andromonoecious species with trimerous flowers; and Martiodendron fluminense, a species lacking the inner whorl of stamens. We also performed a literature review and herbarium specimen survey of the inflorescence and floral morphology of the other 15 genera in Dialioideae. Among the exclusive traits of Apuleia found here are the absence of two sepals and petals from initiation, the simultaneous initiation of the sepals (never before documented for Dialioideae), the absence of carpel initiation in staminate flowers and the formation of the carpel in the staminal whorl of monoclinous flowers, with the presence of a nectariferous hypanthium in both flower types. In Martiodendron the two exclusive traits are the heteromorphic development of stamens of the outer whorl, with the abaxial one being the last to elongate, and the possible initiation of an inner staminal whorl, which stops developing immediately thereafter and is no longer visible at anthesis. Among the potential synapomorphies for the subfamily are the absence of bracteoles and a pair of bracts subtending a triad of flowers or inflorescence axes, the distichous anthotaxy of the thyrsoid inflorescences, the bidirectional initiation of the sepals and the simultaneous initiation of the stamens.