Isoprene emission characteristics of tall and dwarf bamboos

Abstract

Considerable isoprene emissions from several bamboo species have been reported. However, bamboos are highly diverse in taxonomy and have different niches or habitats among species, and the present investigation might be insufficient to conclude a representative isoprene emission trait for bamboos. In this study, isoprene flux, leaf mass per area (LMA), photosynthetic rate, and electron transport rate (ETR) observations were conducted for 18 species within five genera of bamboo species, which include different growth types (tall and dwarf) and climates of the region of origin (temperate, warm-temperate, and subtropical). As a result, we observed that dwarf bamboos exhibited very low or no emission; in contrast, tall bamboos demonstrated considerable isoprene emission fluxes mainly in August and September 2019 at temperatures greater than 30 °C. For tall bamboos, isoprene emission fluxes, photosynthetic rate, and ETR in area-based units were correlated with LMA. To exclude the systematic correlation among isoprene emission flux, photosynthetic rate, and ETR, correlations among the observations of mass-based units were also tested, and the results demonstrated significant positive correlations. The distinction in isoprene emission traits between tall and dwarf bamboos was independent of LMA, photosynthetic rate, and ETR, as there was no difference between them. This implies that the distinction in isoprene emission was caused by genetic differences. The low emission of isoprene from the dwarf species is reasonable because dwarf bamboos usually grow in areas with relatively low heat stress and low light where the production of isoprene could be futile due to carbon loss. This study suggests separating the two bamboo types into different functional types of isoprene emissions.