ISSN:
1399-3054
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
The roots of a mature, field-grown maize plant are dimorphic: the primary root and those from the oldest nodes are bare with a heavily lignified cortex arid sloughed epidermis; those from younger nodes, except for a bare elongation zone, have an intact epidermis surrounded by a persistent soil sheath. Sheathed roots consistently have more layers of cortical cells, but the ratio of volumes of cortex to stele (ca 4) and the cross-sectional area of phloem (ca3× 10−2 mm2) are similar in each type. Assimilated carbon (from 14C applied to a small area of one leaf) was translocated to all roots and actively metabolized in cortex and stele of both types. After 1 to 2 days the proportion of 14C exuded from a given length of mature root into its soil sheath, or into the adjacent unattached soil in the case of bare roots, was the same (5%) in both root types when compared with the ethanol-soluble 14C in the tissues of this length. Up to 75% of the ethanol-soluble label in the roots was in a cationic fraction (amino acids and unidentified compounds), ca 1% was in an anionic fraction and the remainder was in a neutral fraction (sugars). Approximately equal amounts of soluble 14C were found in the stele, cortex and laterals.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1399-3054.1985.tb08661.x
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