The control of carbon acquisition by roots

J. F. Farrar, D. L. Jones

Research output: Contribution to journalReview articlepeer-review

272 Citations (Scopus)


We review four hypotheses for the control of carbon acquisition by roots, and conclude that the functional equilibrium hypothesis can offer a good description of C acquisition by roots relative to shoots, but is deficient mechanistically. The hypothesis that import into roots is solely dependent on export from the shoot, itself determined by features of the shoot alone (the 'push' hypothesis), is supported by some but not all the evidence. Similarly, the idea that root demand, a function of the root alone, determines import into it (the 'pull' hypothesis), is consonant with some of the evidence. The fourth, general, hypothesis (the 'shared control' hypothesis) - that acquisition of C by roots is controlled by a range of variables distributed between root and shoot - accords with both experiment and theory. Top-down metabolic control analysis quantifies the control of C flux attributable to root relative to source leaf. We demonstrate that two levels of mechanistic control, short-term regulation of phloem transport and control of gene expression by compounds such as sugars, underlie distributed control. Implications for the impact of climate change variables are briefly discussed.

Original languageEnglish
Pages (from-to)43-53
Number of pages11
JournalNew Phytologist
Issue number1
Publication statusPublished - 1 Jul 2000
Externally publishedYes


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