PLANT PHYSIOLOGY , Vol 112, Issue 2 623-631, Copyright © 1996 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
Effect of Sulfur Nutrition on the Redistribution of Sulfur in Vegetative Soybean Plants
Sunarpi and J. W. Anderson
School of Botany, La Trobe University, Bundoora, Victoria 3083, Australia
Soybean (Glycine max L.) plants were grown with sulfate at 2 (S2) or 20
[mu]M (S20) and treated with [35S]sulfate between d 36 and 38. Growth was
continued with or without 20 [mu]M sulfate (i.e. S2 -> S0, S2 -> S20,
etc.). When the leaves of S20 -> S20 plants were 70% expanded, they
exported S and 35S label from the soluble fraction, largely as sulfate, to
new expanding leaves. However, 35S label in the insoluble fraction was not
remobilized. Very little of the 35S label in the soluble fraction of the
leaves of S20 -> S0 plants was redistributed; most was incorporated into
the insoluble fraction. The low levels of S remobilization from the
insoluble fraction were attributed to the high level of N in the nutrient
solution (15 mM). Most of the 35S label in S2 plants at d 38 occurred in
the soluble fraction of the roots. In S2 -> S0 plants the 35S label was
incorporated into the insoluble fraction of the roots, but in S2 -> S20
plants 35S label was rapidly exported to leaves 3 to 6. It was concluded
that the soluble fraction of roots contains a small metabolically active
pool of S and another larger pool that is in slow equilibrium with the
small pool.
