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Localisation of translocated 14 C in roots and root exudates of field‐grown maize
Author(s) -
McCully M. E.,
Canny M. J.
Publication year - 1985
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.1399-3054.1985.tb08661.x
Subject(s) - stele , endodermis , cortex (anatomy) , xylem , elongation , botany , phloem , epidermis (zoology) , biology , chemistry , horticulture , anatomy , materials science , neuroscience , metallurgy , ultimate tensile strength
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 (ca 3 × 10 −2 mm 2 ) are similar in each type. Assimilated carbon (from 14 C 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 14 C 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 14 C 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 14 C were found in the stele, cortex and laterals.