Responses in growth and phenolics accumulation to lateral bud removal in male and female saplings of Populus tremula (L.) under simulated climate change.

The responses in growth and defense after tissue damage are highly variable in plants depending on species, damaged-tissue type and the intensity of damage. The prevailing abiotic conditions can also influence these responses. In this study, our aim was to examine how the removal of lateral vegetative buds affects the growth and accumulation of phenolics in saplings of the dioecious Populus tremula grown under simulated climate change. For three growing seasons, the saplings were grown under ambient conditions (control), elevated temperature (+2°C) and elevated UV radiation (30%) (UVB and UVA as its control), or a combination of these. In the fourth growing season, all saplings were grown under ambient conditions. The bud removal was performed twice - in summer and autumn - in the third year. The responses of growth and the accumulation of phenolics to the bud removal were measured at the end of the fourth growing season. Removal of 5% of the lateral buds resulted in higher leaf, stem and total plant biomass in both sexes of P. tremula saplings, compared to intact plants. The effects were greater in the temperature-treated plants, especially in the temperature-treated females. The concentrations of flavonoids and condensed tannins were higher in the bud-removed individuals. The concentration of condensed tannins was also higher in the males than in the females, opposite to the concentration of phenolic acids. There was no significant interaction between bud removal and UVB treatment on either growth or phenolics. Our results suggest that plants can allocate resources to both growth and defense simultaneously in response to tissue loss, and that global warming can modify the responses to some extent.

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