High photosynthetic capacity and energy-use efficiency benefit both growth and chemical defense in invasive plants

In nature some successful invasive plants grow faster and are better chemical defenders than native plants, which appears to contradict the conventional theory that plant growth and chemical defense are trade-offs in terms of the allocation of limited resources. Using greenhouse experiments we compared the growth, chemical defensive matters (condensed tannins and total phenolics) and energy-use strategies (construction cost and energy-use efficiency) of four highly noxious invasive plants to their congeneric or co-occurring native species in subtropical China. We hypothesized that the trade-offs between growth and chemical defense in invasive plants are alleviated, and this alleviation benefits from their high photosynthetic capacities and energy-use strategies. Our results showed that all the four invasive plants grew faster than their native counterparts, and three of them had higher condensed tannins and the remaining one had higher total phenolics, indicating the invasive plants achieved both faster growth and stronger chemical defense. Moreover, the growth rate positively related to condensed tannins but negatively to total phenolics in both invasive and native plants, indicating the chemical-specific pattern of the trade-offs. Our results demonstrate that the higher photosynthetic capacity and energy-use efficiency together with lower biomass construction cost facilitated the faster growth and stronger chemical defense in invasive plants, providing an insight for their chemical-specific trade-offs between growth and chemical defense.