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Supply and partitioning of assimilates to roots of Medicago sativa L. and Lotus corniculatus L. under anoxia
Author(s) -
BARTA A. L.
Publication year - 1987
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 - 10.1111/1365-3040.ep11602103
Subject(s) - lotus corniculatus , trefoil , shoot , shading , botany , anaerobic exercise , respiration , biology , anoxic waters , horticulture , chemistry , agronomy , ecology , physiology , art , visual arts
A current explanation of the mechanism of flooding injury to roots suggests that oxygen deficiency depresses the supply of respirable carbohydrates sufficiently to inhibit fermentation. However, even though it has been shown that phloem transport of assimilate is sharply reduced to anaerobic roots, inhibition of assimilate metabolism has also been suggested to be an important factor. This study examines these hypotheses by relating assimilate supply and metabolic activity in anoxic roots of alfalfa ( Medicago sativa L.), a flood‐intolerant species, and birdsfoot trefoil ( Lotus corniculatus L.), a flood‐tolerant plant. Roots were made anoxic (severe O 2 deficiency) for 2, 4 or 6 d and shoots were labelled with 14 CO 2 . Assimilate transport to the roots and metabolism to structural components were significantly decreased in both species in response to anoxia. Trefoil exhibited significantly greater 14 C incorporation into the residue fraction at 4 d anoxia than did alfalfa, and this was consistent with the greater flooding tolerance of trefoil. When assimilate supply to O 2 ‐deficient roots was decreased by shoot shading, shoot fresh weight was reduced by both anoxia and light treatments. Root‐soluble sugars were significantly decreased by shading but were greatly increased in response to anoxia. Root starch concentration also increased under anoxia. Root K + concentration was reduced by anoxia only. The energy status (ATP/ADP) of roots was significantly decreased by shading; however, anoxia reduced the energy status only in unshaded plants. The data indicate that carbohydrate supply to anaerobic roots does not appear to be a limiting factor in the metabolic response of alfalfa roots. Alternatively, metabolism of assimilate in anoxic roots may be an important determinant of survival.