• Home
• Science Strategy
• Science Teams
• Projects
  • Moisture Relations of Seed Longevity (and their Limits; Orthodox Seeds)
• People
• Publications
• Acronyms

Moisture Relations of Seed Longevity (and their Limits; Orthodox Seeds)

Flowers and fruits of Ranunculus sceleratus, one of the species included in the ageing experiments looking at the effects of moisture on seed longevity

This project is one in a series in the theme of 'Preservation Technology'.

The moisture content of seeds determines what physiological processes may be taking place. Fully imbibed seeds, if they are not dormant, will germinate; seeds at slightly lower moisture contents will be capable of metabolic turnover and repair; at lower moisture contents ageing occurs, again at a rate which depends on the moisture content of the seeds since water will be required for ageing reactions either directly as a substrate or indirectly. In terms of equilibrium relative humidity (eRH) or water activity, the effect of changing moisture level on the rate of ageing reactions is constant across species, although in terms of moisture content (amount of water relative to the fresh or dry weight) it varies between species. With further reduction in moisture, a limit may be reached where seed longevity is optimised. The aim of this project is to determine the effects of changes in moisture level (eRH and amount of water) on rates of ageing and, if sufficient seeds are available, determine the point where longevity is optimal.

For larger collections which have already been included in the comparative longevity screen, samples of seeds are removed from storage and aged at 45°C and a range of moisture levels between 10 and 95% RH (number of moisture levels depends on the number of seeds available); samples are taken at regular intervals and a germination test carried out. Non-linear maximum likelihood estimation is used to fit the viability equation,  where v (NED) is the viability after p (days) storage at moisture content, m (% f.wt.); C_W and K are species-specific constants, K is also temperature-dependant. In order to consider the effect of moisture level in terms of eRH, moisture adsorption isotherms are also determined for the collections where possible.

A number of collections have been included in this study so far (due to the low rate of viability loss at low moisture contents, these experiments may take years to complete), with C_W ranging from 3.3 to 5.2 and K ranging from 4.0 to 5.1, including a number of Ranunculus species.

Kew Home | Science Directory | Copyright & Privacy