Abstract
The overexpression of xyloglucanase increased the length of stem, accompaning by a decreased elasticity (Young s modulus) in the growth zone, an increased elasticity in mature tissue, whereas cellulose deposition was enhanced in both regions. Thus, degradation of the xyloglucan network can be a useful strategy for accelerating growth and cellulose content in trees. The phenotype of leaf in the transgenic poplars was changed to sun leaf, which showed smaller size and thicker than that of the wild type. The leaf also showed high photosynthesis rate, high CO2 conductance and low responding speed of stomata. In the grafting test, the accumulation of cellulose was accelerated in the stems of the transgenic poplars with the leaves of the wild type. These results suggest that the activation for sink function affects the source function.