Ultraviolet radiation causes leaf warming due to partial stomatal closure

Abstract

Variation in solar ultraviolet radiation induces a wide-range of plant responses from the cellular to whole-plant scale. We demonstrate here for the first time that partial stomatal closure caused by ultraviolet radiation exposure results in significant increases in leaf temperature. Significant leaf warming in response to ultraviolet radiation was consistent in tomato (Solanum lycopersicum L.) across different experimental approaches. In field experiments where solar ultraviolet radiation was attenuated using filters, exposure to ultraviolet radiation significantly decreased stomatal conductance and increased leaf temperature by up to 1.5°C. Using fluorescent lamps to provide ultraviolet radiation treatments, smaller but significant increases in leaf temperature due to decreases in stomatal conductance occurred in both multi-day controlled environment growth room experiments and short-term (< 2 hours) climate cabinet irradiance response experiments. We show that leaf warming due to partial stomatal closure is independent of any direct warming effects of ultraviolet radiation manipulations. We discuss the implications of ultraviolet radiation-induced warming both for horticultural crop production and understanding broader plant responses to ultraviolet radiation.

Unravelling the neglected role of ultraviolet radiation on stomata: A meta‐analysis with implications for modelling ecosystem–climate interactions

“…Furthermore, the closure of stomata results in a decrease in transpiration and an increase in leaf (Williams et al, 2022) as well as whole vegetation surface temperature (Field et al, 1995). This could potentially amplify plant respiratory processes over assimilatory processes leading to a decoupling between stomatal conductance and photosynthesis and the reduction of net carbon uptake (Marchin et al, 2023).…”

“…It appears that most current, global models underestimate the true reduction of carbon sink capacity during extreme events (Schewe et al, 2019). Apart from reduced sink capacity, stomatal closure leads to reduced transpiration and enhanced leaf (Williams et al, 2022) and surface (Field et al, 1995) warming, potentially further exacerbating negative effects of drought/heatwaves on plant ecosystems (Reichstein et al, 2013).…”

“…However, little is known about UV effects on stomatal morphology and function and the data in the literature are often contradictory. While some studies have shown, that UV mediates stomatal closure (Nogués et al, 1999) and can thus contribute to a higher leaf temperature (Williams et al, 2022), many other studies reported negligible or even stimulatory effects of UV radiation on the degree of stomatal opening (Jansen & Van Den Noort, 2000). The diverse range of responses raises the question of species‐specific UV radiation effects and the role of the applied UV dose as well as the importance of the entire growth environment.…”

Interactive effects of changes in UV radiation and climate on terrestrial ecosystems, biogeochemical cycles, and feedbacks to the climate system

“…Money Maker) compared plants transferred under near-ambient solar UV radiation to those placed in a UV exclusion treatment in the field. Exposure to UV-B radiation led to partial closure of leaf stomatal pores, reducing transpiration and evaporative cooling, and thus increasing leaf temperature by up to 1.5 °C [ 214 ]. These findings are relevant in warmer climates where even small increases in temperature may have substantial consequences for survival of crops [ 215 ], as high temperatures are well-known to negatively affect photosynthesis and growth of many plant species.…”

The benefits of informed management of sunlight in production greenhouses and polytunnels

“…Manipulating spectral quality affects a suite of photoreceptormediated responses that can be tailored to fit tomato growers' requirements, for example, reduced whole plant water use through changes in branching and stomatal closure or increased biomass/ flower production, without the use of plant hormones (Kotiranta et al, 2015;Williams et al, 2022). Transmittance of UV radiation is responsible for improving fruit quality (c +12% weight, yield c +41%) and shelf life (firmness, slower desiccation and decay) of tomatoes (Ibrahim et al, 2018).…”