Humble garden pea helps Kew scientists develop 'cool,' noninvasive diagnostic test of seed quality

By using infrared temperature measurement, seed viability results are achieved 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.

Dr. Ilse Kranner, from Kew's Millennium Seed Bank, and Prof. Gerald Kastberger (University of Graz, Austria) 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 (Pisum sativum) 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 storage 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 were studied with destructive methods that involved 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.

Non-invasive techniques are widely used in medicine, for example CT scans of the body, and some airports also use infrared cameras to detect fever in passengers.

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 (Triticum aestivum) and rape seeds (Brassica napus) were also studied by the British-Austrian team to provide a proof of concept for agricultural seeds.

The seeds of 10% of the world's wild plant flora are safeguarded at Kew's Millennium Seed Bank at Wakehurst Place in West Sussex, with the aim to conserve a maximum of plant diversity for future generations.

Timelapse videos, showing the temperature changes in live and dead seeds, are available to view online www.pnas.org/cgi/doi/10.1073/pnas.0914197107

For more information and to set up interviews please contact Ilse Kranner at Kew's Millennium Seed Bank on +44(0)1444 894157 or email i.kranner@kew.org

Notes to editors

Noninvasive diagnosis of seed viability using infrared thermography
Ilse Kranner, Hugh W. Pritchard (Royal Botanic Gardens, Kew)
Gerald Kastberger, Manfred Hartbauer (Karl-Franzens-Universität Graz)
The Royal Botanic Gardens, Kew is a world famous scientific organisation, internationally respected for its outstanding living collection of plants and world-class Herbarium as well as its scientific expertise in plant diversity, conservation and sustainable development in the UK and around the world. Kew Gardens is a major international visitor attraction. Its landscaped, 132 hectares and RBG Kew's country estate, Wakehurst Place, attract nearly 2 million visitors every year. Kew was made a UNESCO World Heritage Site in July 2003 and celebrated its 250th anniversary in 2009. For further information please visit www.kew.org.

Wakehurst Place is also home to Kew's Millennium Seed Bank, the largest wild plant seed bank in the world. RBG Kew and its partners have collected and conserved seed from 10 per cent of the world's wild flowering plant species (c. 30,000 species). The aim is to conserve 25% by 2020 and funds are being actively sought in order to continue to develop this vital work. For further information please visit www.kew.org/msbp