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Lack of C 4 photosynthetic metabolism in ears of C 3 cereals
Author(s) -
BORT J.,
BROWN R. H.,
ARAUS J. L.
Publication year - 1995
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.1365-3040.1995.tb00571.x
Subject(s) - photosynthesis , bract , anthesis , hordeum vulgare , biology , triticale , context (archaeology) , cultivar , poaceae , agronomy , botany , horticulture , inflorescence , paleontology
There is continuing controversy over whether a degree of C 4 photosynthetic metabolism exists in ears of C 3 cereals. In this context, CO 2 exchange and the initial products of photosynthesis were examined in flag 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 CO 2 compensation concentration at 210 mmol mol −1 O 2 in durum wheat and barley ear parts was similar to or greater than that in flag leaves. The O 2 dependence of the CO 2 compensation concentration in durum wheat ear parts, as well as in the flag leaf blade, was linear, as expected for C 3 photosynthesis. In a complementary experiment, intact and attached ears and flag leaf blades of barley and durum wheat were radio‐labelled with 14 CO 2 during a 10s 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 CO 2 mainly by the Calvin (C 3 ) cycle, with little fixation of 14 CO 2 into the C 4 acids malate and aspartate (about 10% or less). These collective data support the conclusion that in the ear parts of these C 3 cereals C 4 photosynthetic metabolism is nil.