The biophysical basis of seed longevity
Seed deterioration during storage is an inevitable and irreversible process. The rate of seed deterioration depends on external factors (relative humidity and temperature) and internal factors (genetics and seed quality). Seed treatments (e.g. priming) can also influence seed storage potential. It is very important to determine the storage potential of each seed lot, prior to storage in gene banks, to anticipate the loss of seed quality during the storage period. The most common approaches in the prediction of seed storability are tests based on accelerated aging or controlled deterioration.
However, both methods are time and labour consuming and sometimes have a low predictive value. For this reason there is a continuing interest in identifying new physiological, biochemical or biophysical characteristics of seeds as markers of seed longevity.
It is commonly accepted that the primary damage that occurs in seed aging is auto-oxidation of membrane lipids. Different species may have different levels of protection of their membrane lipids and, thus, different longevity. Weakening of protective mechanisms due to environmental stresses during seed development, harvesting and post-harvesting conditions or seed priming may be the cause of the variations in storability among seed lots.
In this project we study the cellular mechanisms that can reduce oxidative damage in seeds. The efficiency of these mechanisms can be used as markers of seed storability. We study different mechanisms which provide chemical stability of seeds in relation to oxidative damage to membranes. The study is carried out both on seed physiological and physical chemical levels using in vivo Electron Spin Resonance (ESR) and Nuclear Magnetic Resonance (NMR) techniques. With the aid of spin-probes, which respond in a very sensitive way to properties of the membrane and its environment (ESR), as well as detection of the relevant (membrane) components (NMR), the above mentioned mechanisms may be identified. Based on the information obtained from these studies we expect to be able to propose seed characteristics, which can be used as cellular markers of seed longevity. These markers may form the basis of practical testing of seed storability. This project is a collaboration with the Lab of Biophysics at WUR.