Herbivory mitigation through increased water‐use efficiency in a leaf‐mining moth–apple tree relationship

Abstract

Herbivory alters plant gas exchange but the effects depend on the type of leaf damage. In contrast to ectophagous insects, leaf miners, by living inside the leaf tissues, do not affect the integrity of the leaf surface. Thus, the effect of leaf miners on CO 2 uptake and water-use efficiency by leaves remains unclear. We explored the impacts of the leaf-mining moth Phyllonorycter blancardella (Lepidoptera: Gracillariidae) on light responses of the apple leaf gas exchanges to determine the balance between the negative effects of reduced photosynthesis and potential positive impacts of increased water-use efficiency (WUE). Gas exchange in intact and mined leaf tissues was measured using an infrared gas analyser. The maximal assimilation rate was slightly reduced but the light response of net photosynthesis was not affected in mined leaf tissues. The transpiration rate was far more affected than the assimilation rate in the mine integument as a result of stomatal closure from moderate to high irradiance level. The WUE was about 200% higher in the mined leaf tissues than in intact leaf portions. Our results illustrate a novel mechanism by which plants might minimize losses from herbivore attacks; via trade-offs between the negative impacts on photosynthesis and the positive effects of increased WUE.

Hypermetamorphosis in a leaf-miner allows insects to cope with a confined nutritional space

“…This conspicuous arched ridge produces a spacious cavity in which the larva is able to move freely. The body volume of the insect was found to occupy about 3 % of the total mine volume (Pincebourde et al 2006). The tissue-feeder larvae lie on their backs in the mine and feed upwards, chewing out irregular chunks of palisade cells as far as the intact upper epidermis.…”

Friend or Foe? Exploring the Factors that Determine the Difference Between Positive and Negative Effects on Photosynthesis in Response to Insect Herbivory

“…Such a contradictory outcome was deemed to have happened as a result of a transient decoupling of photosynthetic electron transport from carbon assimilation caused by insect damage . Regarding the above, it is not surprising to know that plants can increase WUE as a strategy to ameliorate the negative effects of herbivory, as was recently found in apple tress infested by leaf-mining moths (Pincebourde et al, 2006). Thus, WUE was found to be about 200% higher in the mined apple leaf tissues in comparison to intact leaf portions, prompting the proposal that minimizing water losses reduces the negative impact on photosynthesis derived from herbivore attacks, by avoiding severe reductions in the CO 2 assimilated to water loss ratio.…”

Whole-tree sap flow is substantially diminished by leaf herbivory

“…Pataki et al 1998), which cannot be assumed to accurately reproduce plant responses to real insect feeding, especially from sucking or leaf mining (e.g. Pincebourde et al 2006). We found no other studies that examine the eVect of insect leaf herbivory on a measure of whole-tree water use.…”