Comprehensive evaluation of anatomical structure and photosynthetic characteristics of leaves from five superior Camellia oleifera lines

Correlation analysis and comprehensive evaluation were conducted on leaf anatomical structure and photosynthetic characteristics of five Camellia oleifera superior lines, and the relationship between leaf anatomical structure and photosynthetic capacity of five Camellia oleifera superior lines was explored, and the superior lines with the best photosynthetic characteristics were screened, so as to provide scientific basis for subsequent breeding, cultivation and popularization.

By artificial cross pollination between ‘Sanhua’ and ‘Xianglin 210’, five superior lines of Camellia oleifera were selected, namely ‘Huashi’ (‘Huashuo’ × ‘Huajin’), ‘Huazeng’ (‘Huajin’ × ‘Xianglin210’), ‘Huatuo’(‘Huajin’ × ‘Xianglin210’), ‘Huafeng’ (‘Huashuo’ × ‘Huaxin’) and ‘Huaping’ (‘Huajin’ × ‘Huaxin’). The chlorophyll content, stomatal characteristics, leaf anatomical structure and photosynthetic characteristics of the five superior lines were determined. Finally, correlation analysis and principal component analysis were used to analyze the five superior lines of Camellia oleifera.

It was found that ‘Huatuo’ had the highest leaf shape index, ‘Huashi’ had the largest leaf area, and the total chlorophyll content (10.06 mg·g^-1) was significantly higher than that of the other four superior lines of Camellia oleifera. ‘Huafeng’ had the best stomatal density (10.80/mm²), and the upper epidermis thickness of ‘Huazeng’ was the largest. However, the leaf thickness (523.23 μm), spongy tissue thickness (288.22 μm), palisade tissue thickness (171.40 μm) and transpiration rate of ‘Huaping’ were higher than those of the other four superior lines of Camellia oleifera. Correlation analysis showed that the net photosynthetic rate of leaves is negatively correlated with the thickness of palisade tissue and the ratio of palisade to leaf, and positively correlated with the thickness of leaves, the thickness of the upper and lower epidermis and TRPS. Principal component analysis showed that the cumulative contribution rate of four principal components extracted from 10 leaf traits reached 85.530%, among which the first, second, third and fourth principal components reflected 29.422%, 27.329%, 18.203% and 10.576% of the original data information, respectively, which could fully reflect the leaf anatomical structure and photosynthetic characteristics of Camellia oleifera superior lines. Based on the principal component analysis method, the comprehensive score of each superior line is calculated, and the order is ‘Huaping’, ‘Huatuo’, ‘Huafeng’, ‘Huazeng’ and ‘Huashi’ according to the comprehensive score from high to low.

This study revealed the relationship between leaf anatomical structure and photosynthetic characteristics of superior lines of Camellia oleifera, and screened the superior line ‘Huaping’ with the best photosynthetic characteristics, which provided an important reference for the breeding of improved varieties of Camellia oleifera. Future research should further combine multi-trait comprehensive evaluation and consider the influence of environmental conditions to improve the comprehensiveness and reliability of the research.