Anatomical characteristics of young stems and mature leaves of dwarf pear

• The dwarf pear showed smaller vessels and lower density than standard type.
• The cortical parenchyma cells of dwarf pear were thick in wall and short in length.
• Parenchyma cells of cortex and pith deformed and loosely arranged in dwarf pear.
• The dwarf pear had thicker leaves and thicker palisades than standard type.

The anatomical characteristics of young stems and mature leaves of dwarf and standard pears were compared through light microscopy (paraffin sections) and scanning electron microscopy to understand the tissue structure of dwarf pear inherited from ‘Le Nain Vert’ (Pyrus communis L.). Compared with the standard type, the dwarf type showed a larger stem cross-sectional area but a smaller wood/bark ratio. The dwarf type exhibited more cell layers in both collenchyma and cortical parenchyma than the standard type. The dwarf type also had lower vessel diameter and vessel density than the standard type. Longitudinal sections showed that the dwarf type had shorter vertical length of cortical parenchyma cells and thicker cell wall than the standard type. The cells of the cortical parenchyma and pith parenchyma of the dwarf type were deformed and loosely arranged, and numerous cavities were formed in the tissue. Furthermore, the dwarf type had thicker leaves and palisades with more cell layers than the standard type. The results of this study are essential to further elucidate the physical, biochemical and molecular mechanisms of the dwarf tree architecture.

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