Insects and fungi on a C₃ sedge and a C₄ grass exposed to elevated atmospheric CO₂ concentrations in open‐top chambers in the field

Abstract

The effects of elevated atmospheric CO 2 concentration on plant-fungi and plant-insect interactions were studied in an emergent marsh in the Chesapeake Bay. Stands of the C 3 sedge Scirpus olneyi Grey. and the C 4 grass Spartina patens (Ait.) Mobl. have been exposed to elevated atmospheric CO 2 concentrations during each growing season since 1987. In August 1991 the severities of fungal infections and insect infestations were quantified. Shoot nitrogen concentration ([N]) and water content (WC) were determined. In elevated concentrations of atmospheric CO 2 , 32% fewer S. olneyi plants were infested by insects, and there was a 37 % reduction in the severity of a pathogenic fungal infection, compared with plants grown in ambient CO 2 concentrations. S. olneyi also had reduced [N], which correlated positively with the severities of fungal infections and insect infestations. Conversely, S. patens had increased WC but unchanged [N] in elevated concentrations of atmospheric CO 2 and the severity of fungal infection increased. Elevated atmospheric CO 2 concentration increased or decreased the severity of fungal infection depending on at least two interacting factors, [N] and WC; but it did not change the number of plants that were infected with fungi. In contrast, the major results for insects were that the number of plants infected with insects decreased, and that the amount of tissue that each insect ate also decreased.

MORE EFFICIENT PLANTS: A Consequence of Rising Atmospheric CO2?

“…However, while reduction in foliage [N] has the benefit of increasing NUE, it also has the consequence that it may reduce quality or palatability for grazers. The sedge, S. olneyi, grown in elevated C a , was less often the target for egg deposition and larval grazing than in those in current ambient C a (211). Growth in elevated C a increased phenolics and tannins as well as toughness of the tissues in Eucalyptus sp., and the beetle Chrysophthartus flaveola fed this material did poorly: The low nutritional status resulted in lower body weight, reduced digestive efficiencies, and increased mortality (127).…”

Climate change and plant diseases

“…There is a significant increase in the photosynthetic rate and a decrease in the transpiration rate per unit leaf area, while total plant transpiration sometimes increases, due to the larger leaf area (Jwa & Walling, 2001;Li et al, 2003). The alterations also include higher efficiency in the use of water and nitrogen by the plant (Thompson & Drake, 1994). The stimulus on photosynthesis is due to the reduction in competition between the atmospheric CO 2 and O 2 being fixed by the ribulose 1,5-bisphosphate carboxylase-oxygenase (RUBISCO) enzyme.…”

“…Thompson et al (1993) studied these interactions for the powdery mildew on wheat, caused by Erysiphe graminis, in England. Thompson & Drake (1994) evaluated C 3 and C 4 plants regarding infestation by insects and fungal disease severity as a function of water and N contents. In a factorial FACE experiment, Mitchell et al (2003) assessed the effects of increased CO 2 concentration, nitrogen input and ecosystem species diversity on the occurrence of foliar fungal diseases in C 3 and C 4 plants.…”

Effects of elevated carbon dioxide and arbuscular mycorrhizal infection onTrifolium repens

“…In Scirpus olneyi (Curtis, Drake & Whigbam, 1989;Thompson & Drake 1994). Glycine max (Allen et al, 1988).…”