Kew Gardens and Graz University researchers develop non-invasive test for seed quality

Research lead

Scientists from the Millennium Seed Bank at Kew Gardens in London and Graz University, Austria, have developed a rapid, new method to diagnose seed quality non-invasively and in real time.

Using infrared temperature measurement, seed viability results can be completed in less than two hours. Until now time-consuming germination tests, taking up to three days, were used to assess seed quality. Conventional tests are also destructive, which is not ideal when assessing the seeds of rare and endangered plants.

Ilse Kranner, from the Seed Bank, and Gerald Kastberger of Graz University found that infrared cameras can be used to detect subtle changes in temperature when seeds take up water. These changes vary with viability.

The thermal profiles of hundreds of garden pea seeds were recorded. For each individual seed 22,000 images were analysed to construct a library of thermal fingerprints that allowed the scientists to distinguish between viable and dead seeds in less than two hours.

When a dry seed takes up water, the sugar within the seed dissolves, and this process cools the seed down. The temperature of a single pea seed falls rapidly by 2 to 3°C. Viable seeds maintain cool temperatures because they break down stored reserves into sugar.

In aged seeds, certain biophysical properties are affected that determine the speed of water uptake. Aged seeds also fail to break down their reserves, or can only break them down after a phase of repair, delaying the thermal profile.

To date such processes have been studied with destructive methods that involve grinding up seeds, whereas the new infrared-based method is a breakthrough in the non-invasive diagnosis of seed quality. It means viable seeds can be separated, re-dried and stored again.

Importantly, the opportunity to select live and dead seeds prior to germination is a useful tool to improve studies into the fundamental principles of ageing and cell death, which are similar in plants, animals and humans. This research can potentially be applied in areas such as cancer research.

Wheat and rape seeds were also studied by the British-Austrian team to provide a proof of concept for agricultural seeds.

The seeds of 10 per cent of the world's wild plant flora are safeguarded at Kew’s Millennium Seed Bank, with the aim of conserving a maximum of plant diversity for future generations.