Growth & Development

Formation of branching systems in broad-leaf bamboo

What are the underlying processes that give rise to the different branching architecture types found in the genus Sasa?

Clarifying how plants construct aerial shapes, such as branching architecture, is crucial to understanding how branching contributes to plant adaptation to environments. Architectural analysis is a powerful tool that allows us to decompose the branching process and reveal the underlying processes that give rise to branching architecture. This approach enables us to connect macroscopic features of branching morphology with cellular-level processes. Ideally, such analyses are performed on closely related plant species with differing branching patterns. The genus Sasa, also called broad-leaf bamboo, contains three major sections that exhibit characteristic branching architectures and are distributed separately across the Japanese archipelago, corresponding to snow accumulation. Sasa is therefore a perfect model to investigate how developmental processes and environmental conditions determine branching architecture.

This mass flowering resulting in the plant death of the genus Sasa was observed by the authors on Hokkaido Island, Japan in 2007. The genus reproduces asexually by rhizome for more than several decades until flowering. The photograph is provided courtesy of Dr. Masatomo Nishikori, Forestry Research Institute, Hokkaido Research Organization Japan.

In their newly published work in AoBP, Niimiya & Kawabata document their long term observational study on the development of Sasa branching architecture on Hokkaido Island, with more than 30 years of observations of plant architecture from 1979 to 2012. The results revealed that the three characteristic branching systems of the genus develop mainly through four endogenous processes (distribution of lateral buds on a culm, internode length arrangement, determination of the fate of lateral buds, development of branching with culm fragility) and in response to the snow accumulation. These processes were found to be coordinated with each other over the life span of a single shoot in developing branching architecture. The authors highlight that such correlated development of branching systems is unique, compared with those of other plants, which tend to have meristems only at shoot tips and in perennating buds.

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