Distribution of Starch in Trunkwood of Catalpa bungei ‘Jinsi’: A Revelation on the Metabolic Process of Energy Storage Substances

Starch is stored in thin-walled tissue of wood for several years or even decades. Starch reserves vary by anatomical structure, growth ring, and tree species. The spatial distribution pattern of starch in Catalpa bungei ‘Jinsi’ wood is unclear. We sampled three C. bungei ‘Jinsi’ trees at the end of the growing season and cut discs from their trunks to stain starch granules in wood ray cells with iodine–potassium iodide. We studied starch content in the ray cells of the trunks’ height position (stump, breast height, and crown base) from pith to bark in four directions (west, east, south, north) of the tree. There was a significant difference in starch content in three trunk height positions (p < 0.01), with stump (4.06 to 92.16%) > breast height (6.05 to 69.05%) > crown base (3.89 to 47.04%). There was a significant difference in starch content in different directions at the same height position. In the radial direction, the starch content of sapwood was much higher than that of heartwood, and the starch content showed an overall decreasing trend from bark to pith. The results indicated that starch distribution in tree trunks is uneven, which is related to energy metabolism processes, especially heartwood formation. This will contribute to further research on improving wood quality through the C. bungei ‘Jinsi’ tree breeding program.