The Impacts of Fluctuating Light on Crop Performance

Abstract

Rapidly changing light conditions can reduce carbon gain and productivity in field crops because photosynthetic responses to light fluctuations are not instantaneous. Plant responses to fluctuating light occur across levels of organizational complexity from entire canopies to the biochemistry of a single reaction and across orders of magnitude of time. Although light availability and variation at the top of the canopy are largely dependent on the solar angle and degree of cloudiness, lower crop canopies rely more heavily on light in the form of sunflecks, the quantity of which depends mostly on canopy structure but also may be affected by wind. The ability of leaf photosynthesis to respond rapidly to these variations in light intensity is restricted by the relatively slow opening/ closing of stomata, activation/deactivation of C 3 cycle enzymes, and up-regulation/down-regulation of photoprotective processes. The metabolic complexity of C 4 photosynthesis creates the apparently contradictory possibilities that C 4 photosynthesis may be both more and less resilient than C 3 to dynamic light regimes, depending on the frequency at which these light fluctuations occur. We review the current understanding of the underlying mechanisms of these limitations to photosynthesis in fluctuating light that have shown promise in improving the response times of photosynthesis-related processes to changes in light intensity.

Terrestrial biosphere models may overestimate Arctic CO2 assimilation if they do not account for decreased quantum yield and convexity at low temperature

“…The irradiance and temperature conditions required to induce photoprotection, or cause photodamage in plants is complex, as are the conditions determining the dynamics and magnitude of the recovery process. Both induction and recovery are dependent upon a myriad of additional factors, for example leaf angle, leaf orientation, leaf canopy position, the proportion of direct and diffuse irradiance, the recent irradiance and temperature to which the plants have acclimated, season and leaf age (Bongi & Long, 1987;Long et al, 1994;Garbulsky et al, 2011;Williams et al, 2014;Wong & Gamon, 2015a,b;Slattery et al, 2018). The dynamics of recovery are highly variable, ranging from rapid (min to h) recovery from photoprotection or prolonged (days) depression of photosynthetic performance following severe photodamage (Bolharnordenkampf et al, 1991;Farage & Long, 1991;Groom & Baker, 1992;Ogren & Evans, 1992;Long et al, 1994;Zhu et al, 2004;Takahashi & Murata, 2008;Kromdijk et al, 2016;Slattery et al, 2018).…”

Converging phenomics and genomics to study natural variation in plant photosynthetic efficiency

“…Long‐term light fluctuations include changes in weekly weather conditions and even seasonal variation, which affect plant development and photosynthetic efficiency. Recent insights into mismatches between incoming light and the ability to put that energy into use in carbon assimilation as a result of light fluctuations showed that these can cause considerable growth penalties and reduction in photosynthetic carbon assimilation in photoautotrophic organisms (Zhu et al ., ; Graham et al ., ; Vialet‐Chabrand et al ., ; Taylor and Long, ; Morales et al ., ; Slattery et al ., ). This has been further demonstrated in Arabidopsis plants that lack functional genes involved in photoprotection and light adaptation, such as in the PsbS npq4‐1 (Li et al ., ) and glucose 6‐phosphate / phosphate translocator 2 ( gpt2 ) (Athanasiou et al ., ) mutants.…”

“…Decreasing leaf chlorophyll content to allow more radiation into the canopy is a possible route to improving canopy photosynthetic efficiency (Ort et al ., , ). This should result in minor reductions in overall photosynthetic efficiency while significantly saving on nitrogen input (Slattery et al ., ; Walker et al ., ). Therefore, this trait has received considerable attention in GWAS (Dhanapal et al ., ; Hao et al ., ; Lin et al ., ; Wang et al ., ).…”

The Dynamic Plant: Capture, Transformation, and Management of Energy

“…Two must-read Updates on photosynthetic dynamics caused by fluctuations in irradiance review the salient physiology and promising strategies for improving photosynthesis in crop canopies (Kaiser et al, 2018;Slattery et al, 2018). One possible strategy is to optimize the use of sunflecks within the lower part of the canopy.…”