High Fiber Content is Utilized as Defense Against Folivory in Fagaceae But Not in Salicaceae
Jahant-Miller, Chelsea J.
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This study has important agricultural implications on reducing incidence of leaf damage done by folivorous insects. Increasing foliar fiber content in some crops could be an efficient method for non-chemical pest control. As a leaf matures in the spring it experiences a rapid increase in fiber content. Fiber, found embedded in the cell wall, provides many services for the plant, including structural support, transfer of nutrients, and defense against herbivory. As a defense mechanism, fiber acts to slow the rate at which an herbivore is able to consume the plant tissue and reduces the herbivore’s ability to extract nutrients. In red oak, the rapid increase in leaf fiber is accompanied by a decrease in protein assimilation efficiency (PAE) for the herbivores that feed on it. In this study, we first confirmed the rapid increase in fiber levels that red oak (Fagaceae) experiences during the spring. Next, we examined the effect of fiber in hybrid poplar on the PAE for herbivores that consume it. Poplar trees (Salicaceae) were grown outdoors and the leaves of those trees were fed to gypsy moth larvae (Lymantria dispar). We determined that fiber levels do not rise to sufficient levels in poplar leaves for PAE to be affected. Following those results, we ran similar experiments under the hypothesis that members of the Salicaceae family do not experience a dramatic increase in fiber upon maturation. Similar to the previous experiment, we found that fiber levels in the four Salicaceae species that we tested do not increase sufficiently for the PAE of the larvae that feed on them to be affected. Finally, we compared the lignin maps of each of the four Salicaceae species so that we could visually determine the most digestible portion of the leaves.