Adventitious sprouting enables the invasive annual herb Euphorbia geniculata to regenerate after severe injury

Euphorbia geniculata, an annual weed of arable land native to America and invasive in subtropical and tropical regions, is able to regenerate from seeds and is also able to produce adventitious buds on the hypocotyl. Whether sprouting from adventitious buds represents a mechanism for surviving severe injury, and whether this ability is crucial for species invasion is, however, not known. The significance of such sprouting was investigated with a field survey and a pot experiment. Among 897 plants in 25 field populations surveyed in Indonesia, only a few exhibited marks of injury and sprouting from adventitious buds. When seeds were collected from 12 of the populations and used in a pot experiment, however, the seedlings were able to survive severe injury (removal of all tissue above the hypocotyl) by sprouting from adventitious buds on the hypocotyl and were able to set seed, although they produced less vegetative and generative (flowers and fruits) biomass than control plants. Growth but not fitness of plants in the pot experiment was population specific but neither growth characteristic correlated with disturbance level assessed in the field. Although the pot experiment indicates that E. geniculata can cope with severe injury by adventitious sprouting from the hypocotyl, the survey data are inconsistent with the hypothesis that such adventitious sprouting is important for the plant’s invasion in tropical regions.