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Does light‐promoted export from Commelina benghalensis leaves result from differential light‐sensitivity of the cells in the mesophyll‐to‐sieve tube path?
Author(s) -
Bel Aart J. E.,
Koops Andries J.,
Dueck Tom
Publication year - 1986
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1986.tb02448.x
Subject(s) - sucrose , sieve tube element , biophysics , asparagine , chemistry , membrane , botany , biochemistry , biology , amino acid , phloem
In contrast to the light‐promoted uptake by mesophyll cells, light slightly inhibited sucrose uptake by stripped leaf disks of Commelina benghalensis L. This phenomenon appeared to result from a light‐promoted vein‐associated release, as light stimulated photosynthate release from stripped disks and inhibited that from mesophyll cells. In the ‐presence of the resorption‐blocker p ‐chloromercuriphenylsulfonic acid, (PCMBS) the release of preloaded [ 14 C]‐sugars (sucrose, glucose) and [ 14 C]‐amino acids (alanine, asparagine, proline, valine, α‐aminoisobutyric acid) from stripped disks was doubled in the light. Illumination enhanced by 20 to 60% the release of endogenous leaf cell compounds (sucrose, H 2 PO‐ 4 , K + , Mg 2+ , Ca 2+ ) from stripped disks in the presence of PCMBS. Light also increased the export of [ 14 C]‐assimilates from intact leaves by 20% after pulse‐labelling with 14 CO 2 . A model for loading is proposed, based on the differential light sensitivities of the plasma membranes in the mesophyll‐to‐sieve tube path.