Changes in Photochemical Efficiency in Response to Herbivory and Experimental Defoliation in the Dioecious Tree Ilex aquifolium

Changes in photosynthetic performance following partial defoliation may play a role in alleviating the negative effects of herbivores. We investigated effects of simulated and larval herbivory and the different spatial pattern of leaf tissue removal on the photosynthetic efficiency in the dioecious holly tree. We also addressed whether effects of herbivory on photosynthesis were sex specific. Experiments were conducted with third-year plants growing under natural light and temperature. Photosynthesis was evaluated by chlorophyll fluorescence parameters. Larval herbivory significantly increased the maximum quantum yield of photosystem II and decreased minimum fluorescence (Fo), while experimental defoliation had exactly the opposite effect. The effect of experimental defoliation on the effective quantum yield of photosystem II was significantly influenced by previous herbivory and time. The effect of larval herbivory on Fo changed significantly with time and plant gender. Our results indicate that compensatory photosynthesis can be affected by which kind of damage occurs, the light-adaptation state of plants, the timing of data collection, and plant gender. In the literature, these effects have created misunderstandings because they have not been properly accounted for. Our study illustrates the need to rethink approaches to estimating compensatory photosynthesis and its potential ecological consequences.