Assessment of Plant Responses to Simulated Combination of Heat Wave and Drought

Background: Among the consequences of global climate change, one of the most significant yet understudied is the increased frequency and intensity of heat waves. This article evaluates the responses to combined heat wave and drought in several crops and a non-crop species using an improved methodology to control temperature using IR lamps. Results: The effectiveness and precision of simulated heat waves with the system presented were verified at the experimental field of the University of the Balearic Islands. Using IR lamps, an artificial leaf was used to precisely control environmental temperature, a key aspect in simulating heat wave conditions. Concerning plant physiology, the effects of combined heat wave and drought on leaf relative water content (RWC) and photosynthetic parameters presented different patterns between species. Two remarkable particularities were (1) the observation that photosynthesis was sustained under RWC values well below those previously reported to cause complete photosynthesis cessation in C3 species and (2) the photosynthetic linear electron transport rate (ETR) was stimulated after retrieval of drought and heat wave far above their own initial values and those for control plants, also in some species. Conclusions: The use of an artificial leaf as major temperature sensor is key to provide highly realistic simulated heat waves. Using this technical setup, it was possible to determine that there is a large variability among species and some particularly intriguing observations strongly support the view that systematic experiments should be developed on different species and conditions to grab a significant knowledge on how will heat waves affect crop and vegetation in the near future.