Abstract:Sunflecks are transient patches of direct radiation that provide a substantial proportion of the daily irradiance to leaves in the lower canopy. In this position, faster photosynthetic induction would allow for higher sunfleck-use efficiency, as is commonly reported in the literature. Yet, when sunflecks are too few and far between, it may be more beneficial for shade leaves to prioritize efficient photosynthesis under shade.We investigated the temporal dynamics of photosynthetic induction, recovery under shad… Show more
“…Because they are acclimated to shade, leaves in the lower tree canopy also tend to become light saturated more readily under high light (Boardman, 1977; Earles et al ., 2017). Their acclimation to low irradiance involves a physiological trade‐off that leaves them slower to react to a change in light conditions (Durand et al ., 2022). These factors reduce their capacity to use flecks of light efficiently.…”
Section: Discussionmentioning
confidence: 99%
“…The stand is composed of trees from four provenances: Blaviksliarna southern Sweden, Eichelberg and Rindelpholz in Germany, and Montejo de la Sierra, in Spain. The plot was thinned by removing half of the trees in May 2020 (for more information, see Durand et al ., 2022).…”
Section: Methodsmentioning
confidence: 99%
“…Plants canopies are ever‐changing environments where steady conditions are an exception rather than the norm (Kaiser et al ., 2018; Murchie & Ruban, 2020; Durand et al ., 2022). Even under a clear sky at the very top of a canopy, a light breeze will cause leaves to move and change the relative angle of incidence of sunlight, affecting the irradiance they receive and the leaf boundary‐layer conductance.…”
Summary
Wind‐induced movement in the canopy produces rapid fluctuations in irradiance, called ‘windflecks’. They create a dynamic environment for photosynthesis that bears little resemblance to the stable controlled conditions under which plants are typically measured.
We recorded time series of irradiance to assess the diversity of windfleck properties (intensity, duration, frequency, clustering, and spectral composition) in canopies of four crops and five tree species. We also measured traits associated with leaf morphology and canopy architecture, which could be associated with canopy‐specific differences in windflecks.
Distinct features of windfleck properties were identified both between and among crop and tree canopy. Windflecks in crops were generally more intense and longer, and baseline irradiance was much higher than even the peak irradiance during a windfleck in a forest. The change in spectral composition during a windfleck was species‐specific. Overall, irradiance fluctuations were less frequent and less intense in tall canopies and with increased depth from the canopy.
Our systematic exploration of how canopy structure dictates light dynamics provides new insight into windfleck creation. Coupled with progress in elucidation of the mechanisms of photosynthetic induction, this knowledge should improve our capacity to model canopy ecophysiology and understand light use efficiency in shade.
“…Because they are acclimated to shade, leaves in the lower tree canopy also tend to become light saturated more readily under high light (Boardman, 1977; Earles et al ., 2017). Their acclimation to low irradiance involves a physiological trade‐off that leaves them slower to react to a change in light conditions (Durand et al ., 2022). These factors reduce their capacity to use flecks of light efficiently.…”
Section: Discussionmentioning
confidence: 99%
“…The stand is composed of trees from four provenances: Blaviksliarna southern Sweden, Eichelberg and Rindelpholz in Germany, and Montejo de la Sierra, in Spain. The plot was thinned by removing half of the trees in May 2020 (for more information, see Durand et al ., 2022).…”
Section: Methodsmentioning
confidence: 99%
“…Plants canopies are ever‐changing environments where steady conditions are an exception rather than the norm (Kaiser et al ., 2018; Murchie & Ruban, 2020; Durand et al ., 2022). Even under a clear sky at the very top of a canopy, a light breeze will cause leaves to move and change the relative angle of incidence of sunlight, affecting the irradiance they receive and the leaf boundary‐layer conductance.…”
Summary
Wind‐induced movement in the canopy produces rapid fluctuations in irradiance, called ‘windflecks’. They create a dynamic environment for photosynthesis that bears little resemblance to the stable controlled conditions under which plants are typically measured.
We recorded time series of irradiance to assess the diversity of windfleck properties (intensity, duration, frequency, clustering, and spectral composition) in canopies of four crops and five tree species. We also measured traits associated with leaf morphology and canopy architecture, which could be associated with canopy‐specific differences in windflecks.
Distinct features of windfleck properties were identified both between and among crop and tree canopy. Windflecks in crops were generally more intense and longer, and baseline irradiance was much higher than even the peak irradiance during a windfleck in a forest. The change in spectral composition during a windfleck was species‐specific. Overall, irradiance fluctuations were less frequent and less intense in tall canopies and with increased depth from the canopy.
Our systematic exploration of how canopy structure dictates light dynamics provides new insight into windfleck creation. Coupled with progress in elucidation of the mechanisms of photosynthetic induction, this knowledge should improve our capacity to model canopy ecophysiology and understand light use efficiency in shade.
“…Measurements were done in an open area, using a CCD array spectroradiometer Maya 2000 Pro (Ocean Optics, Dunedin, FL, USA) attached to a cosine diffuser (D7-H-SMA, Bentham Instruments Ltd., Reading, UK). For more information about the measurements, please see [7] , [8] , [9] . Modeled data for Fig.…”
“…1 a that natural leaves exhibit low transmittance characteristic in the visible light waveband. In order to ensure that the natural leaves inside the canopy of vegetation absorb enough PAR for photosynthesis, certain leaf distribution structures are developed, so that sunlight can enter the canopy through the gaps between the outermost leaves of the canopy, and the leaves inside the canopy can receive PAR from the sunflecks to promote the photosynthesis of the entire canopy 25 , 26 . Figure 1 ( a ) Solar spectral reflectance and transmittance of Cinnamomum leaves.…”
Solar spectral reflectance and transmittance of natural leaves exhibit dramatic similarity. To elucidate the formation mechanism and physiological significance, a radiative transfer model was constructed, and the effects of stacked mesophyll cells, chlorophyll content and leaf thickness on the visible light absorptance of the natural leaves were analyzed. Results indicated that light scattering caused by the stacked mesophyll cells is responsible for the similarity. The optical path of visible light in the natural leaves is increased with the scattering process, resulting in that the visible light transmittance is significantly reduced meanwhile the visible light reflectance is at a low level, thus the visible light absorptance tends to a maximum and the absorption of photosynthetically active radiation (PAR) by the natural leaves is significantly enhanced. Interestingly, as two key leaf functional traits affecting the absorption process of PAR, chlorophyll content and leaf thickness of the natural leaves in a certain environment show a convergent behavior, resulting in the high visible light absorptance of the natural leaves, which demonstrates the PAR utilizing strategies of the natural leaves. This work provides a new perspective for revealing the evolutionary processes and ecological strategies of natural leaves, and can be adopted to guide the improvement directions of crop photosynthesis.
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