Abstract:
:Four cell types from Vicia faba Linnaeus "Long Pod" leaflets were assayed for three enzymes unique to the photosynthetic carbon reduction pathway. The enzymes were ribulosebisphosphate carboxylase [3-phospho-D-glycerate carboxy-lyase (dimerizing), EC 4.1.1.39], phosphoribulokinase (ATP:D-ribulose-5-phosphate 1-phosphotransferase, EC 2.7.1.19), and glyceraldehyde-phosphate dehydrogenase (NADP(+)) (phosphorylating) [D-glyceraldehyde-3-phosphate:NADP(+) oxidoreductase (phosphorylating), EC 1.2.1.13]. On a dry weight basis, these enzyme activities were about twice as high in palisade as in spongy parenchyma. Two of the enzymes were not detected in epidermal cells and the other was present in only a trace amount. In guard cells, these enzyme activities were absent or present at les than 1% of the amount in palisade cells. Immunoelectrophoresis showed that ribulosebisphosphate carboxylase was absent in extracts of guard cell protoplasts. Microscopy confirmed the abundance of typical guard cell chloroplasts. These results demonstrate the absence of the photosynthetic carbon reduction pathway in guard cell chloroplasts. This is the only chloroplast type known to be deficient in this pathway in plants whose primary CO(2) acceptor is ribulose bisphosphate. Possible reasons for the absence of this pathway in guard cells are discussed.
journal_name
Proc Natl Acad Sci U S Aauthors
Outlaw WH,Manchester J,Dicamelli CA,Randall DD,Rapp B,Veith GMdoi
10.1073/pnas.76.12.6371subject
Has Abstractpub_date
1979-12-01 00:00:00pages
6371-5issue
12eissn
0027-8424issn
1091-6490journal_volume
76pub_type
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