*2.6. Measurement of Photosynthetic Pigments and Fluorescence Parameters*

Photosynthetic pigments, such as Chl a and b, and carotenoid levels were determined according to the protocol of Lichtenthaler and Buschmann [43]. For pre-experiment bamboo samples, ca. 0.5 g was provided, and then the samples were transferred to a mortar with liquid nitrogen. To prepare the liquid sample extract, the obtained powder was mixed with 20 mL of acetone at a specific concentration of 80% at 0 to 5 ◦C. Then, it was centrifuged at 5000× *g* for 15 min. At the end of the experiment, Chl a, Chl b, and carotenoid levels were determined at absorbances of 663, 645, and 470 nm, respectively. Finally, the levels of Chl and carotenoids were calculated based on the following formulae, which were set in units equal to mg/*g* fresh weight:

$$\text{Chlorophyll a} = 12.25 \text{A663} - 2.79 \text{A647} \tag{2}$$

$$\text{Chlorophyll } \mathbf{b} = 21.50 \mathbf{A} \mathbf{647} - 5.10 \mathbf{A} \mathbf{663} \tag{3}$$

$$\text{Total Chl} = \text{Chl a} + \text{Chl b} \tag{4}$$

$$\text{Carotenoid} = 1000 \text{A} 470 - 1.82 \text{Chl a} - 95.15 \text{Chl b} / 225 \tag{5}$$

A chlorophyll fluorescence imager (CFI) (England) was used to measure fluorescence characteristics, which was conducted under specific dark-adapted conditions for 35 min. To measure the light fluorescence parameters, the fluorescence characteristics were recorded at 700 micromoles m−<sup>2</sup> s−<sup>0</sup> in an illumination incubator for actinic light activation. In this study, the main fluorescence indices were: (i) actual photochemical efficiency of PSll (ϕPSll); (ii) effective photochemical efficiency of PSll (Fv /Fm ); (iii) photochemical quenching coefficient (qP); (4) maximum photochemical efficiency of PSll (Fv/Fm); and (5) non-photochemical quenching (NPQ).
