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Comparison of leaf structure and photosynthetic characteristics of C 3 and C 4 Alloteropsis semialata subspecies
Author(s) -
UENO O.,
SENTOKU N.
Publication year - 2006
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.2005.01418.x
Subject(s) - subspecies , c4 photosynthesis , phosphoenolpyruvate carboxylase , rubisco , photosynthesis , vascular bundle , biology , pyruvate carboxylase , chloroplast , botany , phosphoenolpyruvate carboxykinase , biochemistry , enzyme , gene , zoology
Alloteropsis semialata (R. Br.) Hitchcock includes both C 3 and C 4 subspecies: the C 3 subspecies eckloniana and the C 4 subspecies semialata . We examined the leaf structural and photosynthetic characteristics of these plants. A. semialata ssp. semialata showed high activities of photosynthetic enzymes involved in phosphoenolpyruvate carboxykinase‐type C 4 photosynthesis and an anomalous Kranz anatomy. Phosphoenolpyruvate carboxylase; pyruvate, Pi dikinase and glycine decarboxylase (GDC) were compartmentalized between the mesophyll (M) and inner bundle sheath cells, whereas ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco) occurred in both cells. A. semialata ssp. eckloniana also showed an anomalous non‐Kranz anatomy, in which the mestome sheath cells included abundant chloroplasts and mitochondria. Rubisco and GDC accumulated densely in the M and mestome sheath cells, whereas the levels of C 4 enzymes were low. The activity levels of photorespiratory enzymes in both subspecies were intermediate between those in typical C 3 and C 4 plants. The values of CO 2 compensation points in A. semialata ssp. semialata were within the C 4 range, whereas those in A. semialata ssp. eckloniana were somewhat lower than the C 3 range. These data suggest that the plants are C 3 ‐like and C 4 ‐like but not typical C 3 and C 4 , and when integrated with previous findings, point to important variability in the expression of C 4 physiology in this species complex. A. semialata is therefore an intriguing grass species with which to study the evolutionary linkage between C 3 and C 4 plants.