Changes in soybean gas-exchange after moisture stress and spider mite injury

Changes in soybean gas-exchange after moisture stress and spider mite injury

2003

A:PS

Field experiments were conducted in 1997 and 1998 to understand the physiological responses of soyabean, Glycine max (L.) Merrill, to injury from two-spotted spider mite, Tetranychus urticae Koch, and to examine the contribution of soil moisture toward soyabean tolerance to spider mite injury. A split-plot treatment design was used consisting of moisture stress as the main plot and spider mite injury as the sub-plot treatments in a randomized complete block design with eight replications. Soybeans were moisture-stressed beginning approximately at V10 growth stage, and spider mites were maintained on soybeans for 10 d, and then physiological responses of soyabean were determined. Moisture-stressed soybeans had lower leaf water potentials, photosynthetic rates, stomatal conductances, and transpiration rates. Spider mite injury also caused a significant reduction in photosynthesis, stomatal conductance, transpiration, and chlorophyll content. The lack of a significant impact of spider mite injury on chlorophyll fluorescence and similar light curves, at low light intensities, of soyabean leaves with and without spider mite injury, suggest that spider mite injury does not interfere with the light reaction centre at the initial stage of photosynthesis. Despite measurable reductions in total chlorophyll content from mite injury, fluorescence data and light curves strongly indicate photosynthetic rate reductions from mite injury were not immediately associated with chlorophyll loss or effects on photosynthetic electron transport. There were significant interactions between moisture stress and spider mite injury for some gas-exchange parameters. Photosynthetic rate reductions by spider mites were greater in moisture-unstressed than stressed soybeans. Superimposing spider mite injury did not reduce photosynthetic rates greatly in moisture-stressed soybeans because of an initially low photosynthetic rate from moisture stress. However, comparison of absolute photosynthetic rates of spider mite-injured soyabean leaves with and without moisture stress suggested that soil moisture improved soyabean tolerance to spider mite injury.

v.32(3):433-440, ENVIRONMENTAL ENTOMOLOGY

Research > Published Articles