The maize coleoptiles do not perform typical C₄ photosynthesis: investigation with special reference to anatomy, photosynthetic property, and gene expression

抄録

Maize (Zea mays L.) is one of the most representative C₄ plants. However, several reports have suggested the occurrence of C₃ photosynthesis in this C₄ plant. We examined the photosynthetic characteristics of the coleoptiles, as well as the first, the second, and the third leaves of maize seedlings at their maturities. All the foliage leaves examined, including the first leaf sheath, exhibited representative Kranz anatomy, low CO₂ compensation point, and expression of genes for enzymes involved in the C₄-dicarboxylic acid cycle. In contrast, coleoptiles showed no Kranz anatomy and extremely high CO₂ compensation point. The expression of C₄-specific genes in the coleoptiles was hampered at various levels. These results strongly suggest that the maize coleoptiles do not perform typical C₄ photosynthesis.