Using Leaf Temperature to Improve Simulation of Heat and Drought Stresses in a Biophysical Model

Abstract

Despite evidence that leaf temperatures can differ by several degrees from the air, crop simulation models are generally parameterised with air temperatures. Leaf energy budget is a process-based approach that can be used to link climate and physiological processes of plants, but this approach has rarely been used in crop modelling studies. In this study, a controlled environment experiment was used to validate the use of the leaf energy budget approach to calculate leaf temperature for perennial pasture species, and a modelling approach was developed utilising leaf temperature instead of air temperature to achieve a better representation of heat stress impacts on pasture growth in a biophysical model. The controlled environment experiment assessed the impact of two combined seven-day heat (control = 25/15 • C, day/night, moderate = 30/20 • C, day/night, and severe = 35/25 • C, day/night) and drought stresses (with seven-day recovery period between stress periods) on perennial ryegrass (Lolium perenne L.), cocksfoot (Dactylis glomerata L.), tall fescue (Festuca arundinacea Schreb.) and chicory (Cichorium intybus L.). The leaf temperature of each species was modelled by using leaf energy budget equation and validated with measured data. All species showed limited homeothermy with the slope of 0.88 (P < 0.05) suggesting that pasture plants can buffer temperature variations in their growing environment. The DairyMod biophysical model was used to simulate photosynthesis during each treatment, using both air and leaf temperatures, and the patterns were compared with measured data using a response ratio (effect size compared to the well-watered control). The effect size of moderate heat and well-watered treatment was very similar to the measured values (~0.65) when simulated using T leaf, while T air overestimated the consecutive heat stress impacts (0.4 and 0). These results were used to test the heat stress recovery function (Tsum) of perennial ryegrass in DairyMod, finding that recovery after heat stress was well reproduced when parameterized with T sum = 20, while T sum = 50 simulated a long lag phase. Long term pasture growth rate simulations under irrigated conditions in south eastern Australia using leaf temperatures predicted 6-34% and 14-126% higher pasture growth rates, respectively at Ellinbank and Dookie, during late spring and summer months compared to the simulations using air temperatures. This study demonstrated that the simulation of consecutive heat and/or drought stress impacts on pasture production, using DairyMod, can be improved by using leaf temperatures instead of air temperature.

Response of Some Agronomic, Physiological and Anatomical characters for Some Bread Wheat Genotypes Under Water Deficit in North Delta Region

“…Similar results were reported by Zada et al ( 2020) who stated that drought stress condition considerably reduced the leaf potential and relative water content and transpiration rate with an associated raised in leaf temperature. In general, leaf temperatures were cooler than air temperatures under well-watered conditions, while leaves were warmer than air temperatures under water-stressed conditions (Perera et al, 2019).…”

Heat stress prevented the biomass and yield stimulation caused by elevated CO2 in two well-watered wheat cultivars

“…Thus, plants are unable to cool down and leaf temperatures rise beyond optimum levels causing damage. The negligible effect of HS in our study could be explained by the ability of well-watered plants to maintain leaf temperature below damaging levels due to transpirational cooling (Perera et al, 2019;Deva et al, 2020) even with air temperatures reaching up to 38°C. At moderate (~60%) relative humidity, there is sufficient water vapour gradient to sustain high transpiration rates when soil water is available, as was the case in our experiment.…”

Water relations responses of the pea (Pisum sativum L.) mutant SGECdt to mercury

“…Under water limited conditions, plants decrease stomatal conductance to limit transpiration, thus increasing leaf temperature [21][22]. Although leaf temperature was widely applied to monitor stomatal conductance of laboratory [23] and field-grown plants [24][25], we are not aware of its application to assess the effects of heavy metals on plant water relations. However it was included in comparison study of tree species for phytoremediation potential in soils contaminated by herbicides [26].…”