ISSN:
1365-3040
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
Abstract. The only published consideration of product removal from the soybean root nodule hypothesizes that the peripheral xylem circuit of this determinate nodule structure is flushed by the transpiration stream. However, dyes fed to the transpiration stream through a cut root distal to the nodule do not enter the nodule, and the observed movement of radio-tracers from the root into the nodule can be explained by simple diffusion, Also, there are few xylem elements in the nodule, and these elements are of a small diameter, such that this path can not act as a functional loop of the root system. Further, in this study, nodule vascular strands were never observed to be continuous about the nodule, but were observed to end at the nodule tip in a loop within an intact, closed endodermal sac. Nodule vascular tissue was invested in a pericycle of at least three cell layers. These cells are suggested to be active in the loading of the xylem apoplast with ureides, such that the xylem of the nodule always operates in an export role. Nodule water requirements may be supplied via the phloem or the root cortex apoplasm.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1365-3040.1989.tb01955.x
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