PARENT SESSION
Oral Session 6: Herbivory I: Dynamics, Communities, and Photosynthesis.
Presiding: C Ivey
Monday, August 2, 8:00 AM to 11:30 AM, Meeting Room B 114.

Effects of herbivory on photosynthetic efficiency in Arabidopsis thaliana.

Tang, Jennie^*,1, DeLucia, Evan¹, ¹ University of Illinois at Urbana-Champaign, Urbana, IL

ABSTRACT- The effects of herbivory extend beyond the removal of leaf tissue and include altering photosynthesis in the remaining parts of leaves. Differences in feeding behavior among insect species or developmental stages within a species may affect photosynthesis differently. We compared the effect of 1st and 4th instar Trichoplusia ni larvae on Arabidopsis thaliana; 1st instars make smaller holes than 4th instars and by avoiding veins are less likely to cause localized water stress. For four days following herbivory, photosynthetic efficiency (PSII) was mapped across leaf surfaces by measuring the spatial pattern of chlorophyll fluorescence. In areas of leaves where photosynthesis was inhibited, 4th instar larvae caused a smaller reduction in PSII than 1st instar larvae; it was 6-21% for 4th instars versus 5-49% for 1st instars. In other areas of leaves subject to herbivory PSII often increased slightly and this increase was usually lower for 4th than 1st instar larvae. There was no correlation between the proportion of leaf tissue removed by insects and the magnitude of the reduction of PSII. The reduction in PSII may have been caused by localized water stress, and factors such as the amount of cut edge, the pattern of tissue removed and the type of tissue may affect the magnitude of water stress. In addition to the direct removal of tissues, damage by insects caused a substantial indirect reduction of photosynthesis, and feeding behaviors and the type of feeding guilds may impact photosynthesis in quite different ways.

Key words: Trichoplusia ni, water stress, chlorophyll fluorescence, feeding behavior