Plant chlorophyll fluorescence: active and passive measurements at canopy and leaf scales with different nitrogen treatments

Abstract

HighlightWe studied for the first time the temporal and spatial limits within which active and passive chlorophyll fluorescence measurements are comparable.

Do Daily and Seasonal Trends in Leaf Solar Induced Fluorescence Reflect Changes in Photosynthesis, Growth or Light Exposure?

“…In recent years SIF has been proposed as a means to estimate terrestrial vegetation photosynthetic rates at multiple spatial scales, ranging from the leaf and canopy [5][6][7][8] to global scales [9][10][11][12]. However, changes in SIF fluctuate with the relative proportions of APAR used by plants for photochemistry or NPQ and as such, information about these parameters is needed to interpret SIF [14].…”

“…While the PAM approach is a quick and well established method [3], the saturating light pulse makes it unfeasible for measurements at the large spatial scales required for precision agriculture and plant phenotyping [4]. In recent years, the focus has shifted to the detection of solar induced fluorescence (SIF), which has shown strong potential as a photosynthesis indicator across spatial scales ranging from the leaf and canopy [5][6][7][8] to global scales [9][10][11][12].…”

Estimating Chlorophyll Fluorescence Parameters Using the Joint Fraunhofer Line Depth and Laser-Induced Saturation Pulse (FLD-LISP) Method in Different Plant Species

“…The fibre-HR2000+ was set at a 3 mm distance from the leaf surface, and it was held at 45 • to the fibre-PAM to fully detect the ChlF signal excited by the PAM actinic light. The light pulse intensities of PAM were successively raised from level 1 to 12 (25,45,66,90,125,190, 285, 420, 625, 820, 1150, 1500 µmol m −2 s −1 , respectively) at a duration of about 2 s for each intensity and an interval of 30 s. The integration time of HR2000+ was set at 0.2 s and ΦF at 760.4 nm was obtained by averaging three peak points measured during 2 s. The number of measurements was three times in 20 min dark-adapted leaves and six times in 20 min light-adapted leaves, in which measurements were done four times at about 1300 µmol m −2 s −1 and two times at about 700 µmol m −2 s −1 .…”

“…Still more research is required on both leaf and canopy scales to understand seasonal interplay of ChlF and photosynthesis using both active and passive methods especially when the aim is to relate the knowledge acquired using active techniques to passive techniques [6,66].…”

“…In the FLD method, ChlF parameters cannot be measured and this makes the comparison of active and passive methods difficult [34,47]. Seasonal steady-state ChlF measurement comparison of PAM and FLD methods using outdoor wheat plants in three different treatments showed a weak but statistically significant relationship between active and passive methods, but the FLD measurement presented higher seasonal variability compared to PAM [66]. The authors suggest that these results indicate the complexity of measuring ChlF using passive techniques (FLD) as compared with active methods.…”