Abscisic Acid Regulation of Root Hydraulic Conductivity and Aquaporin Gene Expression Is Crucial to the Plant Shoot Growth Enhancement Caused by Rhizosphere Humic Acids1
An ABA-dependent increase of root hydraulic conductivity and aquaporin expression mediates the plant shoot enhancement caused by dissolved sedimentary humic acids. The physiological and metabolic mechanisms behind the humic acid-mediated plant growth enhancement are discussed in detail. Experiments...
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| Published in: | Plant physiology (Bethesda) Vol. 169; no. 4; pp. 2587 - 2596 |
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| Main Authors: | , , , , , , , , , , , , |
| Format: | Journal Article |
| Language: | English |
| Published: |
American Society of Plant Biologists
08-10-2015
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| Online Access: | Get full text |
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| Summary: | An ABA-dependent increase of root hydraulic conductivity and aquaporin expression mediates the plant shoot enhancement caused by dissolved sedimentary humic acids.
The physiological and metabolic mechanisms behind the humic acid-mediated plant growth enhancement are discussed in detail. Experiments using cucumber (
Cucumis sativus
) plants show that the shoot growth enhancement caused by a structurally well-characterized humic acid with sedimentary origin is functionally associated with significant increases in abscisic acid (
ABA
) root concentration and root hydraulic conductivity. Complementary experiments involving a blocking agent of cell wall pores and water root transport (polyethylenglycol) show that increases in root hydraulic conductivity are essential in the shoot growth-promoting action of the model humic acid. Further experiments involving an inhibitor of
ABA
biosynthesis in root and shoot (fluridone) show that the humic acid-mediated enhancement of both root hydraulic conductivity and shoot growth depended on
ABA
signaling pathways. These experiments also show that a significant increase in the gene expression of the main root plasma membrane aquaporins is associated with the increase of root hydraulic conductivity caused by the model humic acid. Finally, experimental data suggest that all of these actions of model humic acid on root functionality, which are linked to its beneficial action on plant shoot growth, are likely related to the conformational structure of humic acid in solution and its interaction with the cell wall at the root surface. |
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| Bibliography: | The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Jose M. García-Mina (jgmina@unav.es). www.plantphysiol.org/cgi/doi/10.1104/pp.15.00596 These authors contributed equally to the article. M.O. and V.M. performed all of the experiments and prepared and analyzed the data; E.B. and M.G. performed all experiments concerning hormone inhibitors; M.F. and E.C. performed all gene expression analyses; A.M.Z. performed all plant hormone analyses; J.C.I., D.E., I.E., and R.G. performed the analysis of water content and distribution in leaves by using Active THz Imaging-System Analysis; R.B. and J.M.G.-M. contributed to experimental design, data analysis, and discussion; and J.M.G.-M. wrote the article. |
| ISSN: | 0032-0889 1532-2548 |
| DOI: | 10.1104/pp.15.00596 |