Decomposition of Leaves, Stems and Roots of Transgenic Aspen with the Xyloglucanase (sp-Xeg) Gene under Laboratory Microcosm Conditions

Abstract

The genetic transformation of trees by wood modification genes for the improvement of forest plantations results in shifts in plant litter quality. These alterations in plant chemistry lead to changes in decomposition rates, thus affecting the carbon and nitrogen cycling in ecosystems and nutrient availability for plants. To assess the environmental impacts of transgenic trees, we studied the decomposition of plant litter from aspen plants (Populus tremula L.) transformed with the xyloglucanase gene from Penicillium canescens. Mass, carbon and nitrogen losses in the leaves, stems and roots of greenhouse-grown plants were evaluated during incubation in laboratory microcosms. After 12 months of the decomposition experiment, leaves, stems, and roots lost on average 51%, 46%, and 37% of initial mass, respectively. Decomposition of the transgenic stems was not different from wild-type aspen, but we observed significant differences for the leaves (only at the end of the experiment) and the roots (at the early stage). These differences may be related to the nitrogen content and the C/N ratio in the initial samples. Since the litter decomposability determines the availability of nutrients, such alterations should be taken into consideration when cultivating transgenic trees.

Keywords

• Populus tremula
• xyloglucanase
• litter decomposition
• microcosm
• transgenic trees
• nitrogen