Temporal Changes in Soybean Gas Exchange Following Simulated Insect Defoliation
- Robert K. D. Peterson and
- Leon G. Higley
Characterizing the influence of arthropods on plant gas exchange processes, such as photosynthesis, water-vapor transfer, and respiration, is important because these processes are crucial determinants of plant growth, yield, and fitness. Despite the relatively extensive research that has been conducted on physiological responses of soybean [Glycine max (L.) Merrill] to defoliation injury, transient gas exchange parameters, such as photosynthesis, stomatal conductance, and respiration, have not been measured to determine if they are altered after the injury process. A better understanding of these responses would improve the development of plant response models to arthropod stress, which are needed to determine economic injury levels used in pest management programs. Therefore, this study was conducted to characterize the gas exchange responses of soybean following leaf-mass consumption. The study was conducted from 1992 through 1994 on soybean (‘Kenwood’ and ‘Clark’) in a field environment. The experimental design was a randomized complete block with six replications in 1992, four replications in 1993, and seven replications in 1994. Rows were the blocking factor. Various defoliation treatments were imposed using a cork-borer punch. Each treatment replicate was assigned to a leaflet on a separate plant. Gas exchange parameters were measured using a portable photosynthesis system and a steady-state porometer. At approximately 0.25, 1, 3, and 24 h after injury, gross tissue removal did not affect gas exchange parameters of soybean leaflets. Our results support previous research indicating that gross tissue removal does not appreciably alter photosynthetic rates of injured soybean leaves.
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