Anatomical development and biochemical alterations in ribulose bisphosphate carboxylase-oxygenase accumulation during leaf enlargement in Amaranthus tricolor
2001
Wang, Y. (Meijo Univ., Nagoya (Japan). Faculty of Agriculture) | Nii, N.
Anatomical features and biochemical changes in ribulose bisphosphate carboxylase-oxygenase (RuBisCO) accumulation were observed to identify the factors that control photosynthetic activity related to leaf enlargement in Amaranthus tricolor plants. In the upper portion of the leaves, chlorophyll content increased rapidly during the early stages of leaf expansion; the anthocyanin content in the basal green/red portion of the leaves continued to increase during their enlargement. The lamina taken before unfolding consisted of a six-layered plate, which included the abaxial and adaxial epidermises and 4 layers of mesophyll parenchyma. Leaf thickness and palisade cell length approached a maximum when leaf areas reached 20 square cm (about 100 mm in leaf length). The ratio of leaf mesophyll cells to bundle sheath cells decreased rapidly as leaf areas increased. Small starch grains accumulated within the chloroplasts of mesophyll cells, while they gradually accumulated within bundle sheath cells. Immediately after unfolding, many fully differentiated stomata appeared simultaneously. Mature leaves contained higher concentrations of RuBisCO protein than did immature leaves. Before leaf unfolding, RuBisCO protein is localized within the chloroplasts of mesophyll cells. Following differentiation of the bundle sheath, RuBisCO is mainly localized within the chloroplasts of bundle sheath cells. There is little obvious anatomical development of mesophyll tissue between the green portions and the green/red portions of the leaves in A. tricolor.
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