Seasonally varying relationship between sun-induced chlorophyll
fluorescence and photosynthetic capacity from leaf to canopy in a paddy
Photosynthetic capacity (leaf maximum carboxylation rate,
Vcmax) is a critical parameter for accurately
assessing carbon assimilation by plant canopies. Recent studies of
sun-induced chlorophyll fluorescence (SIF) show the potential to
estimate Vcmax at the ecosystem level. However,
the SIF-Vcmax relationship at leaf and canopy
levels are still poorly understood. This study investigates the
relationship between leaf or canopy SIF and leaf
Vcmax and its controlling factors based on SIF
and CO2 response measurements in rice. The results show
that SIF (or its yield, SIFy) and Vcmax are
strongly correlated during the growing season, though the relationship
varies with rice growth stages. After the flowering period, SIFy has a
stronger relationship with Vcmax than SIF flux at
both leaf and canopy levels. Further analysis suggests that changes in
canopy structure and leaf physiology lead to the divergence of the link
between SIF and Vcmax from leaf to canopy level.
Our findings highlight the need to account for plant physiology and
canopy structure in interpreting the SIF signal across spatial scales.
Our observation-based results provide evidence that remotely sensed SIF
observations can be used to track seasonal variations of
Vcmax at the leaf and canopy levels.