Abstract:

Objective: This study aims to establish a quantitative analysis method for the culm form characteristics of Phyllostachys edulis ‘Yuanbao’, and provide a basis for its further study and development and utilization. Method: In this study, a set of approaches was established to quantitatively measure and analyze the internodal length, internodal skew length, internodal diameter, internodal concave depth and internodal oblate index of Ph. edulis ‘Yuanbao’, and the stem shape characteristics of the experimental forest population of Ph. edulis ‘Yuanbao’ planted in Huanggongwang Forestry Garden in Fuyang District, Hangzhou, Zhejiang were tested with these approaches. Result: The results showed that in the range of internodal numbers from 1^st to 30^th, the average internodal length of Ph. edulis ‘Yuanbao increased along with the internodal number, reaching 11.06 cm at the 30^th internode, which amounted to 36.87% of Ph. edulis at the same internodal number. The adjacent internodes alternately skewed to each other in its culms, namely, the length of the same internode varied at different directions, and the internodal length at the two branching sites were the longest or the shortest alternately, while the internodal length on its vertical sites of the branching site changed subtly and was close to the average. Internodal skew length at the base and upper part of culms was shorter, while the skew length of the 9^th to 14^th internodes in the middle of the culm was longer. The average internodal diameter decreased along with the increase in the internodal numbers from 1^st to 30^th. The internodes were usually concave on both sides, the concave depth was lower at the base part, and gradually increased along with the internodal number, reaching the deepest at 10^th to 23^rd internode, and then gradually declined along with the internodal number ascending. In other words, the 1^st to 2^nd internodes concaved slightly at the both branching-sides, and there was no concave on internode between the 2^nd and 3^rd internodes. Subsequently, the concave directions rotated after this site, and the subsequent internodes concaved at the directions vertical to branching site, namely, the 3^rd to 30^th internodes concaved at the sides vertical to branching site, with the deepest depth in internodes from the 10^th to 23^rd. Except 1^st and 2^nd internodes, the upper half of each internode had a wider diameter than the lower half of each internode for 3^rd to 30^th because their lower parts were concaved. The culms were oblate, and the 1^st and 2^nd internodes were near round with subtly oblate at direction vertical to branching site, and the oblate index in upper half was larger than that in lower half of each internode. The oblate direction rotated at a site between 2^nd and 3^rd internodes, and the 3^rd to 30^th internodes were oblate at branching direction with oblate index in upper half smaller than lower half in each internode. The culm’s oblate index enhanced gradually from 3^rd to 15^th internodes, reaching greatest at 15^th to 23^rd internodes, and declined gradually from 23^rd to 30^th internodes, reaching nearly round at the 30^th internode. Rubbing and photo profiles showed waving nodes in the culms. Conclusion: In this paper, a protocol has been established for the measurement and analysis of the skewed and concaved internodes, and oblate culms in Ph. edulis ‘Yuanbao’, which could promote the development of bamboo culm form research, and make up for the shortcomings of the previous method that can only be used for round culm. Detailed and accurate quantitative information of the culm form characteristics of Ph. edulis ‘Yuanbao’ is obtained through this protocol, providing a basis for its further scientific research and development and utilization, as well as a reference for the study of other distinctive bamboos.

Key words: Phyllostachys edulis ‘Yuanbao’, culm form characteristics, quantitative analysis, internodal length, internodal diameter, oblate culms