C4 Grasses: an Anatomical Criterion for Distinguishing Between NADP-Malic Enzyme Species and PCK or NAD-Malic Enzyme Species

Abstract

Transections of leaf blades from 46 C4 grass species of known C4 type were recorded for presence (XyMS+) or absence (XyMS-) of cells intervening between metaxylem vessel elements and laterally adjacent chlorenchymatous bundle sheath cells of primary lateral vascular bundles. A perfect correlation, only 'NADP-ME type' species being XyMS-, indicated that XyMS type serves as a useful predictor of C4 species type. The likely C4 type of 255 biochemically-untyped grass species was accordingly deduced by direct observation (94 spp.) or from Metcalf's anatomical descriptions (161 spp.). All 124 C4 species examined, including C3 eu-panicoids, proved to be XyMS+.

Variations in Km(CO2) of Ribulose-1,5-bisphosphate Carboxylase among Grasses

“…The results are summarized in Table I, where the sample of grasses is arranged according to the best available information on taxonomic relationships above generic level, regarding both the contents of the major groupings and tribes, and (in so far as this can be achieved in a linear arrangement) the sequence of their presentation (16,28 species are indicated by bold face, and those with an asterisk have been biochemically determined to be PCK, NAD-ME, or NADP-ME types (8)(9)(10). The remainder are determined by anatomical criteria (11 Panicum decompositum* (NAD-ME) Panicum miliceum* (NAD-ME) Panicum stapfianum* (NAD-ME)…”

“…RuBP carboxylase was extracted in 100 mm Bicine Buffer (pH 8.0), containing 25 mM MgC12 and 1 mM DTT, and partially purified by elution through Sephadex G-25 in the same buffer. The enzyme was preactivated in 5 mM NaHCO3 and then assayed by measuring the fixation of ['4C]bicarbonate (2) 7 PCK, and 5 NAD-ME), and one C3-C4 intermediate (8)(9)(10)(11). The results are summarized in Table I, where the sample of grasses is arranged according to the best available information on taxonomic relationships above generic level, regarding both the contents of the major groupings and tribes, and (in so far as this can be achieved in a linear arrangement) the sequence of their presentation (16,28 species are indicated by bold face, and those with an asterisk have been biochemically determined to be PCK, NAD-ME, or NADP-ME types (8)(9)(10).…”

“…As part of a comparative and systematic survey of RuBP carboxylase in grasses, an attempt has been made here to discover the extent of Km(CO2) variation, and whether it primarily reflects different photosynthetic pathways, taxonomic relationships, or ecology. Concentration has initially been on grasses (Poaceae), a family whose taxonomic relationships have been thoroughly studied and which incorporates both C3 and C4 plants, including different C4 types (8)(9)(10)(11). Table I were grown from seeds or collected from the field, and their identities were conscientiously checked with reference to appropriate regional floristic works.…”

What Does It Take to Be C4? Lessons from the Evolution of C4 Photosynthesis

“…First, the paramount importance of positional information in relation to vascular development is clear (6), but the positional signals that guide differentiation of complementary cell types remain elusive (Dengler and Nelson in 12). Second, the importance of environmental signals in cell-specific expression of key genes has been recognized, but the effects of light, for example, in different species are as different as day and night (required in Zea, but not in Amaranthus; 13).…”

Biodiversity of Terrestrial Ecosystems in Tropical to Temperate Australia

“…Tropical rainforest flora existed in the wettest areas of the north and north-east [37,38]. Gondwanan C4 grasses and associated flora must have been widespread in the warmer north of the continent [31,[39][40][41][42], while some 14% of the present-day sandstone flora contains woody species in common with the sandstone flora of India ( Figure 2)-and nowhere in between [37,[43][44][45]. Although the southern part of the Australasian Tectonic Plate was located at latitude [60][61][62][63][64][65] • S during the Late Cretaceous, palaeo-oxygen analyses of the sediments in the South Tasman Sea indicate a mean annual temperature of 19.5…”