“Ultraviolet radiation is not all bad news,” according to Lincoln University UV-B expert Professor Brian Jordan, whose research indicates ultraviolet radiation (UV) could be used to enhance the quality of many crops.
UV-B levels vary across the earth’s surface and with changes in altitude. Levels also vary considerably between the two hemispheres, with some sites in the southern hemisphere receiving almost 40% more than comparable latitudes in the northern hemisphere. Adding to the complexity is the wide variety of plant responses to UV-B.
Since the first evidence of a hole in the ozone layer over Antarctica in 1985 leading to increased UV-B reaching the earth’s surface, concerns and perceptions have centred on the damaging consequences and stress caused by excess exposure to UV-B. This has limited exploration of the possibilities to exploit biological responses to UV for agronomic gain.
But the discovery in 2011 of a specific UV-B photoreceptor, one of many mechanisms plants have to mediate acclimation responses, prompted renewed interest in UV worldwide. Professor Jordan says, “Until now UV-B has only been considered as a damaging radiation, but it is now thought to have a more positive role in plant growth and development. Consequently UV-B treatments are being developed as innovative approaches to improve horticulture.”
Despite the unprecedented Montreal Protocol banning CFC’s globally in 1987 and the ‘repair’ of the ozone layer, there is still much debate, research and uncertainty in respect to UV-B levels in the various future climate change scenarios. With so little certainty around levels of radiation in future, research focused on understanding the beneficial aspects of UV-B radiation within the context of food production is crucial. “Key benefits are that UV-B reduces pests and diseases, enhances nutritional value in the form of increased antioxidants and it can be used in glasshouse environments to enhance plant quality and productivity,” says Professor Jordan.
A major research collaboration with Plant and Food Research is aimed at understanding the quality of New Zealand wines, specifically Sauvignon Blanc, and now looking at whether UV-B affects the red grape colour and taste of Pinot Noir wine. Professor Jordan says the unique environment of high light intensity, clear skies and high UV-B can have a profound influence on the biochemistry of New Zealand grape vine cultivars and on the resulting wines. “It is particularly important to understand UV-B induced responses now and in a future climate change scenario.”
Professor Jordan’s research focuses on canopy management - leaf removal which is a common practice to reduce disease pressure - and the relationship to the biochemical composition at harvest. The results show a very strong relationship between UV-B exposure and antioxidant compounds called flavonoids which are important components of wine.
Professor Jordan is also currently involved in a Marsden funded ‘blue sky’ research collaboration with Plant and Food Research into how plants evolved and adapted to their terrestrial environment. The UV environment over the earth’s surface was undoubtedly higher than now when plants moved from an aquatic environment to the land. The major challenge was therefore for these early plants to protect themselves.
The project uses the most sophisticated biochemical and molecular technology to elucidate the nature of the protective compounds and, more importantly, the regulatory mechanisms at the molecular level. It is envisaged that the project will provide novel and fundamental insights into the basis of cellular regulation for UV-B responses. Professor Jordan says, “This project has brought together a great team of talented scientists with a very multi-disciplinary approach to deliver new understanding on UV-B responses through an evolutionary perspective.”
Professor Jordan’s research career in the last 25 years has tracked alongside the broader events relating to UV-B, with his early work on potential UV-B damage to plants associated with ozone depletion leading on to more positive research into the fundamental molecular response to UV-B and the applied aspects for the viticultural industry. “There are so many questions to answer from predicting the influence of UV-B in a changing climate to understanding the responses at a molecular level”.
“One of the greatest advantages and pleasures of my research career working on UV-B has been the international collaboration that I have experienced. Openness and sharing of scientific knowledge will always be the best way to make progress”.