A Plant Notices Insect Egg Deposition and Changes Its Rate of Photosynthesis

Abstract

Scots pine (Pinus sylvestris) is known to change its terpenoid metabolism in response to egg deposition by the sawfly Diprion pini (Hymenoptera, Diprionidae). Three days after egg deposition, parts of the pine twig adjacent to the egg-laden one are induced to emit volatiles, which attract egg parasitoids. In this study, we investigated whether egg deposition by this sawfly affects pine photosynthesis. Measurements of photosynthesis were taken from untreated control twigs and from pine twigs adjacent to egg-laden ones (i.e. systemically oviposition-induced twigs) for a period of 3 d starting after egg deposition. The net photosynthetic rate of oviposition-induced pine twigs was lower than that of untreated control twigs, whereas the respiration rate of pine twigs was not affected by egg deposition. CO 2 response curves of oviposition-induced twigs tended to be lower than those of controls. The potential rate of electron transport ( J max ) and the maximum rate of Rubisco activity (V cmax ) were calculated from the data of the CO 2 response curves. J max of oviposition-induced twigs was significantly lower than that of controls at day 1 after egg deposition, while the difference diminished from day 2 to day 3. A similar pattern was observed for V cmax . Light response curves of oviposition-induced twigs were significantly lower than those of untreated ones during 3 d of measurements. Stomatal conductance was slightly lowered by egg deposition. When considering photosynthetic activity as a physiological currency to measure costs of induction of plant defense, the effects of insect egg deposition on gas exchange of pine are discussed with respect to known effects of insect feeding on the photosynthesis activity of plants.Induced responses of plants to herbivore feeding damage have been studied extensively. These responses include changes in plant chemical composition, phenology, morphology, growth, and photosynthesis (for review, see Karban and Baldwin, 1997). Effects of herbivory on photosynthesis have been studied both on a local scale at the damaged leaf tissue and on a systemic scale by investigating photosynthetic activity of undamaged leaves adjacent to the damaged ones. Local effects measured at leaf tissue structurally damaged by mesophyll feeders, such as Diptera, Hemiptera, or Acari, or at leaf tissue right next to feeding holes produced by chewing insects often show that photosynthetic activity is reduced (Welter, 1989;Zangerl et al., 2002;Haile and Higley, 2003). Many studies on systemic effects of herbivory measured at undamaged leaves adjacent to the sites where chewing herbivores removed leaf material show an enhancement of the photosynthetic rate (Welter, 1989;Zangerl, 1999).In comparison to the effects of insect feeding on plant metabolism, little is known about how a plant responds to insect egg deposition. Gall insects are known to disturb the inner architecture of a leaf by inserting their eggs (Hilker et al., 2002b). In a few cases, insect egg deposition was shown to induce a hypersensitive resp...

Oviposition by a moth suppresses constitutive and herbivore-induced plant volatiles in maize

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Ecophysiological responses of salt cedar (Tamarix spp. L.) to the northern tamarisk beetle (Diorhabda carinulata Desbrochers) in a controlled environment

“…Additionally, the laying of eggs by insects (i.e. oviposition) was found to reduce photosynthesis, but not affect respiration in a study on Pinus sylvestris L. (Scots pine) and Diprion pini L. (sawfly) (Schroder et al 2005). The role of oviposition in affecting leaf gas exchange was not specifically addressed in this experiment, but may have had an effect that offset any compensatory response.…”

Böcek yumurtası ve konukçu bitki arasındaki karşılıklı ilişkiler

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