Fast and small stomata optimise the water use efficiency of sugar beet

Can a better understanding of stomatal physiology make sugar beet more productive and resilient into the future?

Sugar beet is an important annual crop grown in temperate zones around the world, accounting for around 20% of global sugar production. The largest areas of sugar beet (Beta vulgaris ssp. vulgaris) production are in Europe, Russia and North America, where it is grown for both sugar production and biofuel. Although sugar beet yields are increasing in the UK, losses of up to 25 % can still occur in the driest years.

Although quite tolerant to salinity and cold temperatures, sugar beet is surprisingly prone to short-term reversible wilting of leaves. This wilting is driven by the microscopic pores on the leaf surface (stomata) remaining open for photosynthesis when they would normally close in response to lowered water availability. This is termed anisohydric behaviour. Spinach (Spinacia oleracea) belongs to the same family Chenopodiaceae s.s. but demonstrates a more typical isohydric wilting response.

Sugar beet undergoing anisohydric wilting in sunshine and high air temperatures in a field in England, despite the presence of soil water. Anisohydric plants have more variable leaf water potential and keep their stomata open and photosynthetic rates high for longer periods, even in the presence of decreasing leaf water potential. Image credit: Jake Richards.

In their new study published in AoBP, Barratt et al. investigate the roles of stomata in the wilting responses of anisohydric sugar beet and isohydric spinach. They measured the dynamic stomatal responses of both species to step-changes in light intensity. The benefits to the plant are still unclear but, in their study, Barratt et al. show that sugar beet have an adaptation which helps improve function under these conditions.

The authors found that sugar beet possess many small stomata which rapidly respond to changes in light intensity, improving leaf productivity over spinach but also causing the high transpiration rates associated with wilting. As the climate changes, and prolonged dry periods become more frequent, it may be necessary to utilize traits from its wild relative sea beet to breed more water conservative commercial sugar beet varieties.

Researcher highlight

Georgina Barratt undertook a PhD entitled “Understanding the water use efficiency of sugar beet” at the University of Nottingham under the supervision of Prof Debbie Sparkes and Prof Erik Murchie. Georgina has now secured a job with the British Beet Research Organisation as an applied crop scientist. She is involved in applied research and conducts knowledge exchange activities with growers.

Georgina uses her expertise in sugar beet physiology to explore how sugar beet can be adapted to be more resilient under a changing climate. The threat of hotter and drier summers in the UK means that drought tolerance is at the forefront of this work. She aims to convince sugar beet breeders that the UK needs varieties which have drought tolerant traits, especially as much of the sugar beet growing area consists of lighter soils which are prone to drought.

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