Why do wasp induced galls of Acacia longifolia photosynthesise?
type: CreativeWork
description: While many stem and bud galls contain chlorophyll, and have the potential to photosynthesise, these insect-induced growths are generally thought to act as strong carbon sinks, manipulating the normal phloem transport of the host plant in order to serve the demands of the galling herbivore. This study investigated the photosynthetic capacity of bud galls induced by the wasp, Trichilogaster acaciae longifoliae (Pteromalidae) in the invasive Acacia longifolia. The role of this photosynthetic activity was examined in terms of its ability to subsidise carbon budgets, as well as to provide O₂ to the larvae and consume CO₂ in the dense gall tissue, thereby maintaining O₂ and CO₂ concentrations within the range of larval tolerance. Galls were found to contain an overall chlorophyll concentration that was less than half that of subtending phyllodes and a maximum stomata! conductance only 16% that of phyllodes. Gas exchange measurements indicated that while photosynthesis never fully compensated for the respiratory costs of the galls, light-induced carboxylation within galls contributed substantially to the maintenance and growth of galls, especially in the early stages of their development. Very low levels of O₂ were found within the larval chamber and internal tissues of galls, and these levels responded only marginally, if at all, to light, suggesting that the photosynthetic activity of galls does not play a critical role in providing 0 2 to the larvae. The percentage mortality and metabolic response of larvae in reaction to various atmospheres of reduced O₂ and elevated CO₂ indicated that larvae were tolerant of hypoxia and capable of rapidly reducing their respiratory rates to cope with hypercarbia, at least over the short term. Sustained metabolic arrest may, however, have toxic consequences for insects, causing cell damage or even death. The photosynthetic activity of galls substantially reduced internal CO₂ concentrations, thus preventing CO₂ from accumulating within …
abstract: While many stem and bud galls contain chlorophyll, and have the potential to photosynthesise, these insect-induced growths are generally thought to act as strong carbon sinks, manipulating the normal phloem transport of the host plant in order to serve the demands of the galling herbivore. This study investigated the photosynthetic capacity of bud galls induced by the wasp, Trichilogaster acaciae longifoliae (Pteromalidae) in the invasive Acacia longifolia. The role of this photosynthetic activity was examined in terms of its ability to subsidise carbon budgets, as well as to provide O₂ to the larvae and consume CO₂ in the dense gall tissue, thereby maintaining O₂ and CO₂ concentrations within the range of larval tolerance. Galls were found to contain an overall chlorophyll concentration that was less than half that of subtending phyllodes and a maximum stomata! conductance only 16% that of phyllodes. Gas exchange measurements indicated that while photosynthesis never fully compensated for the respiratory costs of the galls, light-induced carboxylation within galls contributed substantially to the maintenance and growth of galls, especially in the early stages of their development. Very low levels of O₂ were found within the larval chamber and internal tissues of galls, and these levels responded only marginally, if at all, to light, suggesting that the photosynthetic activity of galls does not play a critical role in providing 0 2 to the larvae. The percentage mortality and metabolic response of larvae in reaction to various atmospheres of reduced O₂ and elevated CO₂ indicated that larvae were tolerant of hypoxia and capable of rapidly reducing their respiratory rates to cope with hypercarbia, at least over the short term. Sustained metabolic arrest may, however, have toxic consequences for insects, causing cell damage or even death. The photosynthetic activity of galls substantially reduced internal CO₂ concentrations, thus preventing CO₂ from accumulating within …
author: Haiden, Sarah
language: eng
date published: 2011
date modified: 2026-07-24T01:34:16Z
provider: University of Cape Town
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Department of Biological Sciences

PropertyValue
property ID: Handle
value: http://hdl.handle.net/11427/26375