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Comparative ultrastructure and gas exchange characteristics of the C 3 –C 4 intermediate Neurachne minor S. T. Blake (Poaceae)
Author(s) -
HATTERSLEY P. W.,
WONG SUANCHIN,
PERRY S.,
ROKSANDIC Z.
Publication year - 1986
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 - 10.1111/1365-3040.ep11611656
Subject(s) - panicum , poaceae , ultrastructure , botany , crystallography , biology , chemistry
Ultrastructural and physiological characteristics of the C 3 ‐C 4 intermediate Neurachne minor S. T. Blake (Poaceae) are compared with those of C 3 and C 4 relatives, and C 3 ‐C 4 Panicum milioides Nees ex Trin. N. minor consistently exhibits very low CO 2 compensation points (τ: 1.0, usually 0.3–0.6 Pa) yet has C 3 ‐like δ 13 C values. CO 2 assimilation rates (A) respond like those of C 3 plants to a decrease in O 2 partial pressure (2 × 104–1.9 × 103 Pa) at ambient CO 2 levels, but this response is progressively attenuated until negligible at very low CO 2 . By contrast, other species of the Neurachneae are clearly either C 4 (two spp.) or C 3 (seven spp.). For plants grown and measured at different photon flux densities (PFDs), τ for N. minor and P. milioides increases from 0.5 to 1.0, and from 1.0 to 2.1 Pa, respectively, as PFD is decreased from 1860 to 460 μmol m −2 s −1 . In N. minor , the O 2 response of τ is either biphasic as in P. milioides , but much diminished and with a higher transition point, or is very C 4 ‐like. As in C 4 relatives, inner sheath cells contain numerous chloroplasts. Their walls possess a suberized lamella, which may make them more CO 2 ‐tight than bundle sheath cells of P. milioides , contributing to the almost C 4 ‐like τ characteristics of N. minor . The biochemical basis of C 3 ‐C 4 intermediacy is considered.