Imaging pam chlorophyll fluorescence system

The maximum photochemical efficiency of PSII (Fv/Fm) was measured with an IMAGING-PAM chlorophyll fluorescence system (Heinz Walz GmbH, Effeltrich, Germany) using default parameters according to Yu’s [25 (link)]. After tea leaves adapted to the dark for 20 min, Fo was measured. Then, a one-second saturation pulse occurred that completely closed all PSII receptors, and Fm was measured. The maximum photosynthetic efficiency (Fv/Fm) was calculated as:

On the 14th day of the treatment period, photosynthesis was monitored from 10:00 to 11:30 am. We measured the following parameters with the CIRAS-3 portable photosynthetic system (PP Systems, Massachusetts, USA): net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), intercellular CO₂ concentration (Ci) and water use efficiency (WUE). The relative chlorophyll content (SPAD) was measured six times using a SPAD502 instrument, and the average value was calculated.
Samples (0.2 g) were taken from fresh, clean peach leaves and extraction was performed for 24 h in a 95% ethanol solution. We then used a Pharma-Spec UC-2450 ultraviolet spectrophotometer (Shimadzu, Kyoto, Japan) to measure the OD₆₆₅, OD₆₄₉, and OD₄₇₀ of the extract. To calculate leaf chlorophyll and carotenoid levels, we used the methods of Li et al., 2021 (link).
We used the IMAGING-PAM Chlorophyll Fluorescence System (Heinz Walz, Effeltrich, Germany) to measure the following parameters: minimal fluorescence (F0), maximal fluorescence (Fm), maximum quantum efficiency (Fv/Fm), actual quantum efficiency (ΦPSII), photochemical quenching (qP), nonphotochemical quenching (NPQ), and electron transport rate (ETR). To determine Fv/Fm, the peach leaves were dark-adapted in a dark clip adaptor for 30 min.

Chl fluorescence measurements were carried out employing the IMAGING‐PAM Chlorophyll Fluorescence System and imagingwin software (Heinz Walz, Effeltrich, Germany). F_v/F_m measurements were obtained by application of a single saturating pulse to dark‐adapted plants. Average F_v/F_m of the entire rosette was calculated using the imagej macro ‘PHENOPSIS‐Fluo’ (Bresson et al., 2015).