Potato Review

16 POTATO REVIEW MARCH/APRIL 2022 HEAT STRESS Professor of Plant Pathology, Dr Rumiana Ray, highlighted modern potato varieties are adapted to grow at optimum temperatures of between 14⁰C and 22⁰C, with long day conditions. “Elevated temperatures, beyond 28C, can cause profound effects on several physiological development processes,” she said. “Those effects include on stem elongation, inhibition of tuberisation, decrease in the rate of photosynthesis and biomass partitioning.” She explained that the photosynthetically active leaves act as a source of sucrose, translocated by the phloem to the developing tubers, that act as carbohydrate sinks. “However, heat stress or other extreme environmental stress can alter plant hormonal regulation and metabolism leading to reduced translocation of photosynthetic assimilates into the developing tubers. “When you have very high temperatures, beyond 35⁰C, then tuberization can be completely abolished.” The potato plant’s response to environmental stress, including heat stress, is to upregulate photoprotective responses to avoid photoxidative damage in the chloroplasts, Rumiana said. “The plant does this through a process known as non-photochemical quenching (NPQ).This mechanismacts by harmless dissipation of unused energy back into the environment as heat. “Through this process, you may have a competition between photoprotection and photochemistry for this same absorbed energy. That’s why often when we see an increase in NPQ, we see a reduction in the capacity of the plant to drive photochemistry.” Testing techniques Using various tools such as Licor or fluorcam the team at University of Nottingham can measure NPQ and the efficiency of photochemistry as quantum yield along with gas exchange on the leaf to determine photosynthesis. In the glasshouse, under fluctuating temperatures that best represented conditions in the field through the day and night, temperatures could be managed at 28 to 35C. Quantis was applied to plants subjected to elevated temperatures. Researchers measured NPQ and photochemical efficiency, along with stomatal conductance and transpiration to determine the plants response to heat stress. “The first results we observed were that Quantis, 24 hours after application ➜ Dr Rumiana Ray Andy Cunningham Quantis field application timing Quantis trials - Potatoes under heat stress in U of N glasshouses Quantis trials - Licor measure of leaf effciency