Seed high-temperature sensitivity and germination ecology in intermediate seeds of three species from Xishuangbanna, tropical China.

Plant invasion causes changes in floristic composition, and structural and functional degradation of tropical rainforest, which is driven by global changes, deforestation and habitat fragmentation, with temperature increasing as a marked trait in rainforest remnants. Here, we hypothesized that microclimate change, particularly increased temperature, is a major driver for plant invasion to tropical rainforest. Laboratory and field experiments were designed to investigate the germination ecology and high-temperature tolerance of intermediate seeds from three species: Cinnamomum burmanni, Citrus maxima, and Coffea arabica, which are cultivated in Xishuangbanna, tropical China though not native. It was found that the seeds all exhibited sensitivity to high-temperature, including low germination when incubated at ≥ 35 °C or ≥ 9 h daily warm period at 40 °C, and viability loss after ≥ 4 d continuous heating at 40 °C or 30-min heating at temperature ≥ 50 °C, although with interspecific variations. Meanwhile, these species demonstrated a strong preference for forest habitats during plant regeneration from seeds, including higher germination percentage and longer seeds and seedling survival under forest conditions. Overall, intermediate seeds had high-temperature sensitivity, close to or slightly lower than recalcitrant seeds, but markedly higher than orthodox seeds of pioneer and weed species previously reported. We suggest that Cinnamomum burmanni, Citrus maxima, and Coffea arabica all have the potential to enter Xishuangbanna tropical rainforests. [ABSTRACT FROM AUTHOR]