Phenotypic trait variations of Michelia odora from different provenances at the seedling stage and their correlations with geographical-climate factors

This study aims to investigate the phenotypic trait variations of Michelia odora seedlings from different provenances and their correlations with geographical and climatic factors, thereby providing a scientific basis for breeding superior varieties and optimizing seedling cultivation practices.

One-year-old M. odora seedlings from six provenances in Guangxi (Debao, Napo, Fusui, Jinxiu, Jingxi, and Yangshuo) were selected as research subjects. The relationships between growth parameters, leaf functions, photosynthetic characteristics, and geographical environments were analyzed comprehensively.

1) M. odora is a full-growth type. The height growth of seedlings shows a distinct “slow-fast-slow” “S”-shaped growth rhythm, with slow growth from January to March and from November to December, and rapid growth from April to October. The growth pattern of ground diameter is different from that of height, with rapid growth from January to September and slow growth from October to December. The height and ground diameter of Jingxi and Debao provenances are significantly higher than those of other provenances; 2) The leaf area, stomatal density, spongy tissue and net photosynthetic rate of Jingxi provenance are significantly greater than those of other provenances (P<0.05), while the stomatal length, width, stomatal conductance and intercellular CO₂ concentration are significantly smaller than those of other provenances (P<0.05); 3) The variation range of 19 traits of M. odora from six provenances is 10.94%-60.20%, and the coefficient of variation of five traits including height is greater than 40%; 4) The geographical factors (longitude, latitude) of the provenance area are the key factors affecting growth traits, while geographic factors, annual average precipitation and relative humidity are the key factors influencing leaf traits. Latitude and relative humidity are the key factors affecting photosynthetic characteristics. Cluster analysis divided the six provenances into three categories: the first category includes Debao and Jingxi, the second category includes Napo, Jinxiu and Fusui, and the third category includes Yangshuo. The comprehensive analysis of membership function shows that Jingxi provenance has the best growth and photosynthetic capacity.

The phenotypic traits of M. odora seedlings from different provenances are rich in variation, and the variation of M. odora is significantly affected by environmental factors. M. odora responds to the environment by adjusting the variation of leaf phenotypes. Provenances with low latitude and high annual average temperature have excellent growth performance.