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. 1991 Mar;95(3):716–722. doi: 10.1104/pp.95.3.716

Water Relations of Growing Maize Coleoptiles 1

Comparison between Mannitol and Polyethylene Glycol 6000 as External Osmotica for Adjusting Turgor Pressure

Michael Hohl 1, Peter Schopfer 1
PMCID: PMC1077597  PMID: 16668045

Abstract

Water relations of growing segments of maize (Zea mays L.) coleoptiles were investigated with osmotic methods using either mannitol (MAN) or polyethylene glycol 6000 (PEG) as external osmotica. Segments were incubated in MAN or PEG solutions at 0 to - 15 bar water potential (Ψo) and the effects were compared on elongation growth, osmotic shrinkage, cell sap osmolality (OC), and osmotic pressure (πi). The nonpenetrating osmoticum PEG affects πi in agreement with Boyle-Mariotte's law, i.e. the segments behave in principle as ideal osmometers. There is no osmotic adjustment in the Ψo range permitting growth (0 to −5 bar) nor in the Ψo range inducing osmotic shrinkage (−5 to −10 bar). Promoting growth by auxin (IAA) has no effect on the osmotic behavior of the tissue toward PEG. In contrast to PEG, MAN produces an apparent increase in πi accompanied by anomalous effects on segment elongation and shrinkage leading to a lower value for Ψo which establishes a growth rate of zero and to an apparent recovery from osmotic shrinkage after 2 hours of incubation. These effects can be quantitatively attributed to uptake of MAN into the tissue. MAN is taken up into the apoplastic space and the symplast as revealed by a large temperature-dependent component of MAN uptake. It is concluded that MAN, in contrast to PEG, is unsuitable as an extemal osmoticum for the quantitative determination of water relations of growing maize coleoptiles.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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