Abstract
A comprehensive evaluation of the recently developed Fraunhofer line depth (FLD) and laser-induced saturation pulse (FLD-LISP) method was conducted to measure chlorophyll fluorescence (ChlF) parameters of the quantum yield of photosystem II (ΦPSII), non-photochemical quenching (NPQ), and the photosystem II-based electron transport rate (ETR) in three plant species including paprika (C3 plant), maize (C4 plant), and pachira (C3 plant). First, the relationships between photosynthetic photon flux density (PPFD) and ChlF parameters retrieved using FLD-LISP and the pulse amplitude-modulated (PAM) methods were analyzed for all three species. Then the relationships between ChlF parameters measured using FLD-LISP and PAM were evaluated for the plants in different growth stages of leaves from mature to aging conditions. The relationships of ChlF parameters/PPFD were similar in both FLD-LISP and PAM methods in all plant species. ΦPSII showed a linear relationship with PPFD in all three species whereas NPQ was found to be linearly related to PPFD in paprika and maize, but not for pachira. The ETR/PPFD relationship was nonlinear with increasing values observed for PPFDs lower than about 800 μmol m−2 s−1 for paprika, lower than about 1200 μmol m−2 s−1 for maize, and lower than about 800 μmol m−2 s−1 for pachira. The ΦPSII, NPQ, and ETR of both the FLD-LISP and PAM methods were very well correlated (R2 = 0.89, RMSE = 0.05), (R2 = 0.86, RMSE = 0.44), and (R2 = 0.88, RMSE = 24.69), respectively, for all plants. Therefore, the FLD-LISP method can be recommended as a robust technique for the estimation of ChlF parameters.
Highlights
Chlorophyll (Chl) fluorescence (ChlF) measurement is a powerful non-destructive technique used to assess the photosynthetic performance of plants [1,2,3,4,5,6]
We examined the relationships between the actinic photosynthetic photon flux density (PPFD) and chlorophyll fluorescence (ChlF) yields in the dark and solar light adaptation periods for paprika leaves (Figure 3) as the saturation PPFD required to saturate the photosynthetic electron transport varies with the intensity of actinic light
We examined the relationships between SPAD values and ChlF parameters retrieved from Fraunhofer line depth (FLD)-LISP; no significant relationships were found confirming that the ChlF parameters are not affected by
Summary
Chlorophyll (Chl) fluorescence (ChlF) measurement is a powerful non-destructive technique used to assess the photosynthetic performance of plants [1,2,3,4,5,6]. The ChlF principle is based on how light energy, which is absorbed by photosynthetic pigments such as chlorophylls and cartenoids is distributed [10]. Light energy received by Chl a has three main alternative fates; being used in photochemistry, being lost as non-radiative heat dissipation, or being emitted as fluorescence. By measuring ChlF, the efficiency of photochemistry and heat dissipation can be assessed [24]. ChlF offers a direct approach for actual plant photosynthetic activity measurement
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