Osmotic Stability of Mannitol and Polyethylene Glycol 20,000 Solutions Used as Seed Germination Media¹

Abstract

Solutions of mannitol and high molecular weight polyethylene glycols (PEG) of different osmotic potentials are often used to simulate water stress in seed germination studies. However, little has been reported about the osmotic stability of these solutions. The objectives of this study were to determine the osmotic stability of mannitol and PEG 20,000 solutions, to examine the biological significance of any observed instabilities, and to compare osmotic vs. matric water potential effects on germination of winter wheat (Triticum aestivum L., ‘Nugaines’). Four solutions of mannitol, PEG, and KC1 (standard) with water potentials ranging from −3.5 to −18.0 bars were incubated at 10, 20, and 30 C and water potentials were measured periodically with thermocouple psychrometry. In addition, comparisons were made of the percent and rate of germination of wheat seeds placed in 28‐day‐old and freshly prepared solutions of mannitol and PEG and the percent and rate of seedling emergence from a watered soil media. The osmotic potential of different mannitol solutions and of the −9.1‐ and −17.4‐bar PEG solutions did not change with time. However, the osmotic potential of the −4.0‐ and −6.4‐bar PEG solutions decreased 1.0 bar. Percent and rate of germination of wheat was the same in the 28‐day‐old and in freshly prepared mannitol and PEG solutions; but at equal potentials, the germination rate was most rapid in the mannitol solutions. Wheat emergence rate from watered soil was linearly related to the germination rate in PEG, but not in mannitol solutions. Hence the slight instability of PEG solutions appears to be of no biological consequence in seed germination studies, and wheat seed emergence rates at different soil matric potentials can be approximated from germination rates in PEG osmotic solutions.

Water stress induced by mannitol and sodium chloride in soybean cultivars

“…Induced water deficit by polyethylene glycol showed similar values to that observed in the fields (Thill et al, 1979), permitting also vigour evaluation (Santos et al, 1996). In similar potential ranges, germination patterns may be different between species or even between varieties of the same species (McWilliam and Phillips, 1971;Therios, 1982).…”

Effects of water stress on nitrogenase activity in Abuts incana

“…2). The ieaf water potential in PEG treated plants after dark equilibration was the same as calculated for the PEG medium (Thill et al 1979), which means that the water potential was in equilibrium within the whoie system. Figure 1 shows that both nitrogenase activity and stomatal opening were affected by water stress and suggests a reiationship between closure of stomata and decreasing nitrogenase activity.…”

Influência do estresse hídrico simulado com manitol na germinação de sementes e crescimento de plântulas de canola

“…Alguns trabalhos indicam que a simulação da deficiência hídrica imposta pela utilização de soluções com potenciais osmóticos elevados produziu efeitos menos drásticos sobre as plantas do que quando comparados com o mesmo nível de estresse provocado por potencial mátrico de mesma intensidade (Thill et al, 1979). Por outro lado, Braccini et al (1996b), verificaram que o uso de soluções de manitol para simular condições de baixa umidade no solo apresentou resultados satisfatórios com sementes de soja.…”