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 shade, and stomatal movement during a sunfleck, in sun and shade leaves of Fagus sylvatica from three provenances of contrasting origin. We found that shade leaves complete full induction in a shorter time than sun leaves, but that sun leaves respond faster than shade leaves due to their much larger amplitude of induction. The core-range provenance achieved faster stomatal opening in shade leaves, which may allow for better sunfleck-use efficiency in denser canopies and lower canopy positions. Our findings represent a paradigm shift for future research into light fluctuations in canopies, drawing attention to the ubiquitous importance of sunflecks for photosynthesis, not only in lower-canopy leaves where shade is prevalent, but particularly in the upper canopy where longer sunflecks are more common due to canopy openness.

Keywords

canopy vertical gradients; Fagus sylvatica; photosynthetic induction; provenance trial; stomatal dynamics; sun and shade leaves; sunfleck

Published in

New Phytologist
2022, Volume: 235, number: 4, pages: 1365-1378
Publisher: WILEY

SLU Authors

• Stangl, Zsofia Réka

  • Department of Forest Ecology and Management, Swedish University of Agricultural Sciences
    
  • University of Helsinki

UKÄ Subject classification

Forest Science


Publication identifier

DOI: https://doi.org/10.1111/nph.18222

Permanent link to this page (URI)

https://res.slu.se/id/publ/118025