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Physiology of plant tolerance to arthropod injury

Fikru Jiru Haile, University of Nebraska - Lincoln

Abstract

I conducted field and greenhouse experiments in 1997 and in 1998 to examine physiological mechanisms conferring plant tolerance to arthropod injury and to understand the contribution of environmental resources toward plant tolerance to arthropod injury. Studies on tolerant, antibiotic, and susceptible wheat lines to the Russian wheat aphid, Diuraphis noxia (Mordvilko), indicated that the tolerant wheat line exhibited photosynthetic compensation compared with the antibiotic or the susceptible wheat lines. Photosynthetic compensation in the tolerant wheat line could be because of rapid healing from aphid injury which allowed this line to maintain photosynthetic rates comparable to those of the uninjured control treatments. The antibiotic wheat line exhibited greater photosynthetic rate reduction by aphid injury, which suggested that there might be trade-offs between antibiotic defense and plant growth. ^ Studies examining the interaction between twospotted spider mite, Tetranychus urticae Koch, injury and moisture stress showed that spider mite injury reduced photosynthesis, stomatal conductance, and transpiration in both moisture-stressed and well-watered soybeans. Well-watered soybeans initially had higher rates of photosynthesis and were more sensitive to spider mite injury than moisture-stressed soybeans. However, because the absolute photosynthetic rates of spider mite-injured soybean leaves were greater in well-watered than in moisture-stressed soybeans, soil moisture improved the tolerance of soybeans to spider mite injury. ^ Studies on sunflower and soybean gas-exchange responses to defoliation and moisture stress demonstrated that gas-exchange responses varied based on plant water status. In both sunflower and soybean, moisture-stressed plants had lower leaf water potential and hence lower photosynthetic rates. However, the impact of defoliation on photosynthesis was variable depending on changes in plant water status. When defoliation was performed on most leaves per plant, plant water potential improved and enhanced photosynthetic rates occurred. Conversely, when defoliation was performed on an individual leaf per plant, plant water status did not improve and defoliation did not significantly alter photosynthetic rates. Significant yield loss occurred in both moisture-stressed and well-watered soybeans due to defoliation. However, well-watered plants produced more leaf tissues and tolerated defoliation more than moisture-stressed plants. ^

Subject Area

Agriculture, Agronomy|Biology, Ecology|Biology, Entomology|Agriculture, Plant Pathology|Biology, Plant Physiology

Recommended Citation

Haile, Fikru Jiru, "Physiology of plant tolerance to arthropod injury" (1999). ETD collection for University of Nebraska - Lincoln. AAI9942125.
http://digitalcommons.unl.edu/dissertations/AAI9942125

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