Journal Article

Sucrose transport in the phloem: integrating root responses to phosphorus starvation

John P. Hammond and Philip J. White

in Journal of Experimental Botany

Published on behalf of Society for Experimental Biology

Volume 59, issue 1, pages 93-109
Published in print January 2008 | ISSN: 0022-0957
Published online January 2008 | e-ISSN: 1460-2431 | DOI:
Sucrose transport in the phloem: integrating root responses to phosphorus starvation

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Sugars in plants, derived from photosynthesis, act as substrates for energy metabolism and the biosynthesis of complex carbohydrates, providing sink tissues with the necessary resources to grow and to develop. In addition, sugars can act as secondary messengers, with the ability to regulate plant growth and development in response to biotic and abiotic stresses. Sugar-signalling networks have the ability to regulate directly the expression of genes and to interact with other signalling pathways. Photosynthate is primarily transported to sink tissues as sucrose via the phloem. Under phosphorus (P) starvation, plants accumulate sugars and starch in their leaves. Increased loading of sucrose to the phloem under P starvation not only functions to relocate carbon resources to the roots, which increases their size relative to the shoot, but also has the potential to initiate sugar-signalling cascades that alter the expression of genes involved in optimizing root biochemistry to acquire soil phosphorus through increased expression and activity of inorganic phosphate transporters, the secretion of acid phosphatases and organic acids to release P from the soil, and the optimization of internal P use. This review looks at the evidence for the involvement of phloem sucrose in co-ordinating plant responses to P starvation at both the transcriptional and physiological levels.

Keywords: Deficiency; mineral; nutrient; phloem; phosphate; phosphorus; signal; starvation; sucrose

Journal Article.  10690 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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