Abstract: [Objective]Thirteen clones of the Section Aigeiros were selected from plantation at the age of 3 years to investigate leaf anatomical properties (thickness of palisade and spongy parenchyma layers and total leaf), stomatal properties(density and length of stomata) at 3 canopy positions (upper, middle and lower canopy) and growth traits,in order to analyze the genetic variation and correlation between various leaf traits and growth traits, and to carry out indirect selection on growth traits. [Method]Uniform rooted stocks with 1-year-old stem and 2-year-old roots were planted with a randomized block design, with 3 replications and 25-tree plots (5 rows×5 columns),at a spacing of 3 m × 5 m. Two average trees were selected from each block. According to the top-down order of natural branching, the canopy was divided into 3 layers, i.e. upper, middle and lower canopy. A representative branch was selected from the first-order branches on the south side at each canopy position of each average tree. Leaf traits were examined for a mature leaf on each selected representative branch. Data were evaluated by analysis of variance and relationships by Pearson's correlation coefficient. Principal Components Analysis (PCA) was performed with 11 traits, including growth traits (3- and 4-year-old DBH) and leaf traits at the upper, middle and lower canopy positions, separately. [Result]Height and DBH of 1 to 4 years old trees, leaf anatomical traits, stomatal density and length varied significantly among clones and three canopy positions. The palisade parenchyma layer was thicker than the spongy parenchyma layer for most clones and irrespective of canopy position. All clones had a higher stomatal density and similar stomatal length on the abaxial leaf surface than on the adaxial leaf surface. For most clones, leaves in upper canopy had thicker leaf palisade, spongy parenchyma layer and higher stomatal density than these in lower canopy. DBH of 1- to 4-year-old trees were negatively and significantly correlated with abaxial stomatal density at three canopy positions, while correlation coefficient (r) between DBH of 3-year-old and 4-year-old trees with abaxial stomatal density at middle canopy were -0.755 and -0.736. DBH of 2-year-old tree was positively correlated with adaxial stomatal density at higher canopy position (r=0.402), while there was no significant relationship between DBH of 1- to 4-year-old tree and adaxial stomatal density at middle and lower canopy positions. DBH of 1- and 3-year-old tree was positively correlated with spongy parenchyma thickness at middle canopy position (r=-0.319, -0.339). However, there was no significant relationship between DBH of 1- to 4-year-old trees with palisade parenchyma thickness, total leaf thickness and adaxial/abaxial stomatal density at different canopy positions. The first 3 components of PCA (PC₁, PC₂ and PC₃) of 11 traits established for upper, middle and lower canopy positions independently explained 82.7%, 87.5% and 88.3% of the variability. With PC₁ and PC₂ as the comprehensive factors, the 13 clones were divided into 3 groups, and 7 clones were selected.These clones displayed the highest growth, lower abaxial stomatal density, higher adaxial stomatal density and stomatal length, and smaller spongy parenchyma thickness. [Conclusion]As the variation of growth traits and leaf traits among clones and the relationships between growth traits and leaf traits at different canopy positions were significant, the leaf traits at different canopy positions significantly correlated with growth traits could be used for indirect selection of growth traits of clones of the Section Aigeiros.

Key words: Section Aigeiros, leaf anatomical properties, stomatal density, stomatal length, growth, canopy position