Crassocephalum crepidioides, Conyza canadensis, and Ageratum conyzoides are alien annuals naturalized in China, which produce a large number of viable seeds every year. They widely grow in Xishuangbanna, becoming troublesome weeds that compete with crops for water and nutrients.
Due to their wide distribution and marked harmfulness as weeds, these three invasive species have been investigated in detail, but very little is known about their adaptation to invaded habitats.
Researchers from Xishuangbanna Tropical Botanical Garden (XTBG) investigated the responses of seed germination in C. crepidioides, C. canadensis, and A. conyzoides to temperature and water stress, in order to increase the knowledge on their advantages and limitations as invasive species.
As seed germination is among the most important life-stages which contribute to plant distribution and invasiveness, the researchers investigated its adaptation to temperature and water stress in the three Asteraceae weeds concurring in Xishuangbanna, SW China. They investigated seed germination requirements and its response to high temperature and water stress in the three invasive species.
They found that germination occurred in these three species over a wide temperature range, with maximum germination occurring at temperature range of 15–30°C. Species, temperature, light, and their interactions all showed a significant interactive effect. Light was a vital germination prerequisite for C. crepidioides and A. conyzoides, whereas most C. canadensis seeds germinated in full darkness.