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GrainGenes Reference Report: PEN-18-697

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Reference	PEN-18-697
Title	Lack of C4 photosynthetic metabolism in ears of C3 cereals
Journal	Plant, Cell and Environment
Year	1995
Volume	18
Pages	697-702
Author	Bort J Brown R Araus J
Abstract	There is continuing controversy over whether a degree of C4 photosynthetic metabolism exists in ears of C3 cereals In this context, CO2 exchange and the initial products of photosynthesis were examined in nag leaf blades and various ear parts of two durum wheat (Triticum durum Desf.) and two six-rowed barley (Hordeum vulgare L.) cultivars. Three weeks after anthesis, the CO2 compensation concentration at 210 mmol mol-1 O2 in durum wheat and barley ear parts was similar to or greater than that in nag leaves. The O2 dependence of the CO2 compensation concentration in durum wheat ear parts, as well as in the flag leaf blade, was linear, as expected for C3 photosynthesis. In a complementary experiment, intact and attached ears and flag leaf blades of barley and durum wheat were radio-labelled with 14CO2 during a 10 s pulse, and the initial products of fixation were studied in various parts of the ears (awns, glumes, inner bracts and grains) and in the flag leaf blade. All tissues assimilated CO2 mainly by the Calvin (C3) cycle, with little fixation of 14CO2 into the C4 acids malate and aspartate (about 10% or less). These collective data support the conclusion that in the ear parts of these C3 cereals C4 photosynthetic metabolism is nil.
Keyword	[ Hide all but 1 of 14 ] aspartic-acid c3-photosynthesis c4-photosynthesis calvin-cycle carbon-dioxide carbon-dioxide-compensation-concentration flag-leaf gas-exchange hordeum vulgare malic-acid photosynthates photosynthesis spikes triticum durum

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