Modelling the Effect of Salt and PEG on Water Uptake in Wheat Seeds

Louis John Irving,Hongxiang Zhang

doi:10.3390/agronomy11081660

Abstract

Water uptake is a seminal process in seed germination. Salt and polyethylene glycol (PEG) are known to retard seed germination rates and percentages, which is often attributed to osmotic effects. Here, we quantified water uptake in wheat seeds killed with a hot needle, finding evidence of three distinct water uptake pools. The fast pool was unaffected by salt, and likely represents cell walls and other apoplastic material. Water uptake into the medium and slow pools was slowed by salt addition, with the medium pool thought to be cellular, while the slow pool is presumably related to endosperm hydration. Salt caused a minor decrease in the water uptake rates and maximum seed water content, while PEG strongly suppressed both parameters. Seeds transferred between water and salt solutions followed the water uptake trajectories of the solution into which they were transferred. Seeds transferred from PEG to water achieved final seed water contents similar to water control seeds, while seeds transferred from water to PEG achieved significantly higher final water contents than PEG controls. This work confirms that salt and PEG have distinct effects on water uptake by wheat seeds.

Highlights

Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China; Abstract: Water uptake is a seminal process in seed germination
Differences in the germination rates and percentages between seeds incubated in salt and polyethylene glycol (PEG) are generally attributed to
It is unclear whether arrested germination is directly due to osmotic effects, or to some nontoxic germination repression caused by the salt, it has been noted that high concentrations of Na+ and Cl− ions can inhibit critical metabolic steps in cell division [8]

Summary

Introduction

Differences in the germination rates and percentages between seeds incubated in salt and PEG are generally attributed to “ionic effects”, which can be either negative or positive. In some halophytic (salt-tolerant) species, incubation in high salt concentrations can arrest germination, germination percentages can often recover when these seeds are transferred to pure water [7]. It is unclear whether arrested germination is directly due to osmotic effects, or to some nontoxic germination repression caused by the salt, it has been noted that high concentrations of Na+ and Cl− ions can inhibit critical metabolic steps in cell division [8]. Moderate salt levels have been shown to promote germination [4], and it has been suggested that salt can be compartmentalized and used as a cellular osmotica, Academic Editor: Cristina Patanè

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Conclusion