Leaf Anatomic Plasticity of White Clover and Its Response to Different Light Intensities

A study was conducted on the leaf anatomic plasticity of white clover (Trifolium repens L.) in response to the heterogeneous habitats, and on the legume leaf anatomic characteristics under different light intensities. Results show that the white clover leaf structure boasts plasticity, more particularly the leaf epidermis and mesophyll, though the leaf middle vein remains relatively stable. Under full sunlight, the white clover leaves share characteristics of sun-facing plants: such as thicker leaf blades, plate outer cells wall in upper epidermis, dense stomas, developed palisade tissue with densely arranged cylinder palisade cells, thinner spongy tissue with tiny and loosely arranged cells, and thicker mid-ribs. Whereas under thinned sunlight, the legume leaves exhibit features of those of shade plants, like thin leaf blades, lens-like upper epidermis cells, loosely arranged stomas, reductive palisade tissue with irregular or funnel-shaped cells, rich spongy tissue of large-sized and densely ranged cells, and thin mid-ribs. Nonparametric correlation analysis indicates that the thickness of upper epidermis and thickness of spongy tissue negatively correlate to the relative light intensity, while stoma density of upper epidermis, thickness of palisade tissue, thickness ratio of palisade and spongy tissue, length and width ratio of palisade cells, and thickness of middle vein positively correlate to the relative light intensity. Leaf anatomy plasticity may contribute to the high ecological adaptation of this widespread species.