This study was conducted on 1-3-year-old C. utilis species. The crown and leaf shape indexes of 30 bamboo samples were collected. The One-way analysis of variance was used to compare the differences between the crown shape (branch length and diameter, angle between branch as well as culm, and angle between branches) and leaf shape (leaf length, width, area and dry weight) indexes of bamboo of different ages. The standardized major axis was used to analyze the allometric relationship between leaf and branch biomass and also between leaf area and leaf dry weight at different ages.

There were no significant differences between the indexes, including angle between branch and culm, angle between branches, branch diameter, and leaf shape of C. utilis at different ages. Since the leaf length, width, area, dry weight and specific leaf area showed an increasing trend with an increase in bamboo age, and these five indexes of 3-year-old bamboo were significantly larger than those of 1-year-old bamboo. On the contrary, the allometric relationship between branch and leaf biomass showed that 3-year-old bamboo was inclined to allocate resources to the leaves. Hence, we found that 3-year-old bamboo had the largest displacement from the common allometric index in terms of the allometric relationship between leaf area and leaf dry weight, which showed that 3-year-old bamboo had the larger leaf area when the leaf dry weight was constant.

We conclude that age has a significant effect on the crown shape, leaf shape, and allometric relationship between the branch and leaf. We suggest that while leaf shape is sensitive to the change in bamboo age, crown shape is relatively slow to change in relation to age. Generally, a 3-year-old C. utilis has large leaf length, leaf width, leaf area, leaf dry weight, and specific leaf area, thus, having high aproductive capacity.