Genets of dwarf bamboo do not die after one flowering event: evidence from genetic structure and flowering pattern

Abstract

Dwarf bamboos in the genus Sasa are believed to be long-lived, synchronously flowering, and monocarpic plants. However, the monocarpy of dwarf bamboo has not been confirmed, because whether all ramets within one genet flower at the same time cannot be determined without differentiating the genetic structure among ramets. This study aims to evaluate the reproductive traits of Sasa pubiculmis by verifying the monocarpy and physiological integration between flowering ramets and non-flowering ramets during a 4-year flowering period. One genotypically identified genet, which covered an area of approximately 3 ha, had both flowering and non-flowering patches of ramets during the 4-year flowering period (2004-2007). A fraction of the flowering genet remained non-flowering during the 4 years of observation, and did not die after mass flowering. Flowering ramets were physically connected to non-flowering ramets via rhizomes, and assimilated (13)C was allocated from non-flowering ramets to flowering ramets. Consequently, we clarified that this dwarf bamboo potentially has polycarpic reproductive traits rather than monocarpic, and a genet can keep rhizomes and non-flowering patches alive to sustain the organism after mass flowering.

Bamboo for people, Mountain gorillas, and golden monkeys: Evaluating harvest and conservation trade-offs and synergies in the Virunga Volcanoes

“…This occurs at 30-40 years of age and involves synchronous patches comprising one or more clones. In some species some rhizomes may persist after flowering (Miyazaki et al, 2009) -but evidence regarding Y. alpina is anecdotal (Wimbush, 1947cited in Kigomo, 1988. Patches of flowering bamboo, comprising a few hectares each, were observed on the slopes of Mt.…”

Clonal Structure, Seed Set, and Self-Pollination Rate in Mass-Flowering Bamboo Species during Off-Year Flowering Events

“…Although the death of flowering culms after off-year flowering has been observed in bamboo [19], it has never been ascertained whether the genets that flowered in off-years were excluded from the bamboo population. Clarification is required as to whether all the culms in a genet flower synchronously in an off-year.…”

“…Studies on the clonal structures of off-year flowering sites are limited in number. Off-year flowering events have only been studied in two bamboo species [19], [20]. There is also a need to determine, by surveying a number of sites, whether multiple genets flower synchronously, even in off-years (but see [19], [20]); if this is the case, cross-pollination may occur.…”

“…A few studies have supported the prediction that reproductive success in off-years seldom occurs in bamboo [19], [21]. However, other studies have reported that over 10% of seeds set even in off-years [16], [22].…”

Estimation of outcrossing rates at small-scale flowering sites of the dwarf bamboo species, Sasa cernua

“…Makita (1998) indicated in terms of evolutionary trends that sexual regeneration gives rise to inter-genet competition in the habitat and affects the life history processes of dwarf bamboos. Regardless of how sexual regeneration can induce gene recombination to produce new genetic diversity, only a limited number of genets can contribute to the mating event in small-scale flowering (Kitamura and Kawahara 2009) or single-genet flowering (Miyazaki et al 2009). This may eventually lead to higher kinship within the population and biparental inbreeding, which reduces the overall fitness of the population (Mukai 1978).…”