Increased photosynthetic performance in holly trees infested by scale insects

Abstract

Summary1. Changes in plant physiological features after herbivory may alleviate the adverse effects of herbivores. We examined the ability of Ilex aquifolium L. (European Holly) plants to compensate for scale insect herbivory through increased photosynthesis. Based on assumptions of the source-sink hypothesis, we predicted that scale insects, by inducing supplementary sinks for photosynthates, would increase photosynthesis. 2. Photosynthetic performance was evaluated by measuring chlorophyll fluorescence parameters in plants growing under natural light and temperature at the field station of the University of Santiago (north-west Spain). We measured photosynthesis on infested leaves of infested trees; scale-free leaves of infested trees; and scale-free leaves of scale-free trees. 3. Insect infestation significantly increased photosynthetic efficiency. Effects of scale insects on photosynthesis were particularly enhanced by high temperature and light. Scale insects also altered the photosynthesis of leaves not directly affected by the insects. 4. Our study showed that changes in the balance between source and sink tissues, induced by scale insects, may partly explain host plant photosynthesis. We suggest that increased feeding rates of scale insects promoted by high temperature and light conditions would increase the carbon demand of infested plants, resulting in greater compensatory photosynthesis.

Impact of scale insect infestation on the content of photosynthetic pigments and chlorophyll fluorescence in two host plant species

“…The feeding of Bemisia tabaci Gennadius reduced the leaf photosynthesis in tomato leaves by decreasing the content and photosynthetic capacity of chlorophyll (Buntin et al 1993). Different results were presented by Retuerto et al (2004) who examined the ability of Ilex aquifolium L. plants to compensate for scale insect herbivory through increased photosynthesis. They investigated the hypothesis that phloem-sap feeding insects, by acting as additional sinks for photosynthate, might increase the photosynthetic rates of their hosts (Crawley 1999).…”

“…The use of chlorophyll fluorescence imaging for rapidly detecting indirect perturbations in leaf metabolism before any effects on growth and development have been detected has increased in recent years (Aldea et al 2006;Tang et al 2006;Delaney 2008;Nabity et al 2009). So far, remarkably little is known about the effects of scale insects on the photosynthetic pigment content and on photosynthesis parameters (Vranjic 1997;Retuerto et al 2004).…”

Effects of sap-feeding insect herbivores on growth and reproduction of woody plants: a meta-analysis of experimental studies

“…Furthermore, the great number of studies on sap-feeder-host plant interactions (e.g. Karban 1980;Retuerto et al 2004;Dungan et al 2007) were conducted by comparing plants showing natural herbivore densities with naturally undamaged plants (i.e. with plants that were avoided by herbivores).…”

“…Unfortunately, some papers based on this method (e.g. Retuerto et al 2004) are frequently cited, which leaves little hope for rapid improvement of research methodology. Like Nykänen and Koricheva (2004), we excluded studies in which plants were assigned to herbivory and control treatments not randomly but according to the extent of the natural herbivore damage they suVered.…”

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

“…In contrast, an experimental setting designed to test the effects of partial de-budding on photosynthesis, stomatal conductance and nitrogen in Picea jezoensis seedlings led to the conclusion that the enhanced photosynthetic rate observed in de-budded seedlings was the result of an increased root/leaf ratio that reduced the stomatal limitation of photosynthetic rate, rather than of an altered sink-source relationship or increased leaf nitrogen content (Ozaki et al, 2004). A pair of studies aimed at determining the carbon costs of herbivory by phloem-feeding scale insects on tress found that infested trees had a greater annual photosynthesis, as determined by measuring parameters such as Vc max, the maximum rate of Rubisco-catalysed carboxylation, J max, the rate of electron transport when irradiance is saturating and/or chlorophyll fluorescence (Retuerto et al, 2004;Dungan et al, 2007). The small negative effect on tree growth and reproduction and increased photosynthetic efficiency observed were taken as an indication that damaged trees were able to compensate fully for the relatively large loss of carbon to herbivory caused by the honeydew insects.…”