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Vascular transport and soybean nodule function: II. A role for phloem supply in product export *
Author(s) -
WALSH K. B.,
CANNY M. J.,
LAYZELL D. B.
Publication year - 1989
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.1365-3040.1989.tb01631.x
Subject(s) - xylem , phloem , nodule (geology) , transpiration , root nodule , nitrogenase , biology , chemistry , botany , nitrogen fixation , photosynthesis , nitrogen , paleontology , organic chemistry
The ureide content of soybean ( Glycine max (L.) Merr.) nodules was unaffected by variations in the transpirational rate, while whole plant manipulations designed to decrease phloem supply to nodules resulted in lower rates of nitrogenase activity and an increase in the ureide content of the nodules. The rate of ureide export from the nodule was estimated from the exponential rate of decrease in the pool size of ureides in nodules, following exposure to an N 2 ‐free atmosphere (Ar:O 2 ). Export was greatly reduced under treatments which reduced phloem supply to the nodule. A water budget for nodules suggested that the delivery of water to the nodule via mass flow in the phloem was comparable to that required for export of ureides from the nodule in the xylem from the nodule. Therefore, we suggest that xylem export from nodules is related to the phloem supply to the nodule rather than to the transpirational flux in the parent root. This suggestion is related to the reported decreases in nodule permeability to gases under conditions of phloem deprivation.