Open AccessSulfur Assimilation in C4 Plants
Author(s) -
Ben C. Gerwick,
Clanton C. Black
Publication year - 1979
Publication title -
plant physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.554
H-Index - 312
eISSN - 1532-2548
pISSN - 0032-0889
DOI - 10.1104/pp.64.4.590
Subject(s) - biochemistry , vascular bundle , pyrophosphate , sulfur , enzyme , assimilation (phonology) , photosynthesis , phosphoenolpyruvate carboxylase , ribulose , chemistry , phosphoenolpyruvate carboxykinase , biology , botany , rubisco , linguistics , philosophy , organic chemistry
The activity of adenosine 5' triphosphate sulfurylase was determined in crabgrass mesophyll cells, bundle sheath strands, and whole leaf extracts. The enzyme was assayed by following molybdate-dependent pyrophosphate release from ATP, (35)SO(4) (2-) incorporation into adenosine 5' phosphosulfate, and ATP synthesis dependent upon adenosine 5' phosphosulfate and inorganic pyrophosphate. With all assays, greater than 90% of the activity was found in extracts from bundle sheath strands. The activities in whole leaf extracts were consistently intermediate between the activities of mesophyll and bundle sheath extracts and extract-mixing experiments gave no indication of enzyme activation or inhibition in vitro. Whole leaf activities were several hundred-fold less than concurrent measurements of ribulose 1,5-bisphosphate and phosphoenolpyruvate carboxylase activities, which is interpreted as being consistent with the relative amounts of elemental carbon and sulfur found in higher plants. A hypothesis is presented for the intercellular compartmentation of sulfur assimilation in relationship to NO(3) (-) and CO(2) assimilation in leaves of C(4) plants.