Uv 1800 model with the cps 240 cell holder

The lipid peroxidation in the celery samples (leaves, petioles, and byproducts), in terms of thiobarbituric acid-reactive substances (TBARSs), was measured with a thiobarbituric acid (TBA) reaction. For this purpose, 3 mL of trichloroacetic acid (TCA) (20% (w/v)) was added to 100 mg of freeze-dried celery tissues. The mixture was homogenized and centrifuged at 3500× g for 20 min. Then, 1 mL of TCA (20%, w/v) containing TBA (0.5%, w/v) and 150 µL of BHT (4%, w/v) in ethanol was added to 1 mL of supernatant and mixed. The homogenate was incubated for 30 min at 95 °C and then cooled on ice and centrifuged at 10,000× g for 15 min. The absorbance of the resulting supernatant was measured at 532 nm using a UV–visible spectrophotometer (Shimadzu UV-1800 model with the CPS-240 cell holder, Shimadzu Europa GmbH, Duisburg, Germany). In addition, the value for the non-specific absorption at 600 nm was recorded. An extinction coefficient of 155 mM⁻¹ cm⁻¹ was used for calculating the concentration of thiobarbituric acid-reactive substances (TBARSs) [18 ]. Results were expressed as TBARSs µmol g⁻¹ FW.

Chlorophylls a and b were extracted from fresh outer and inner-leaf material. Samples (1 g) were homogenized with a solution of acetone–hexane (2:3) (25 mL) by using a Polytron, and centrifuged for 6 min at 5000 x g and at 4°C. The absorbance of the supernatant was measured with a UV/VIS spectrophotometer (Shimadzu UV-1800 model with the CPS-240 cell holder, Shimadzu Europa GmbH, Duisburg, Germany) for chlorophyll a and b at A663, A645, 505 and A453, and concentrations were calculated using equations outlined by Nagata and Yamashita [25 ]:
$$\mathrm{C}\mathrm{h}\mathrm{l}\mathrm{o}\mathrm{r}\mathrm{o}\mathrm{p}\mathrm{h}\mathrm{y}\mathrm{l}\mathrm{l}\mathrm{a}\left(\mathrm{m}\mathrm{g}100\mathrm{m}{\mathrm{L}}^{\mathrm{‐}1}\right)=0.999\mathrm{*}\mathrm{A}663–0.0989\mathrm{*}\mathrm{A}645$$
$$\mathrm{C}\mathrm{h}\mathrm{l}\mathrm{o}\mathrm{r}\mathrm{o}\mathrm{p}\mathrm{h}\mathrm{y}\mathrm{l}\mathrm{l}\mathrm{b}\left(\mathrm{m}\mathrm{g}100\mathrm{m}{\mathrm{L}}^{\mathrm{‐}1}\right)=\mathrm{‐}0.328\mathrm{*}\mathrm{A}663+1.77\mathrm{*}\mathrm{A}645$$
$$\mathrm{L}\mathrm{y}\mathrm{c}\mathrm{o}\mathrm{p}\mathrm{e}\mathrm{n}\mathrm{e}\left(\mathrm{m}\mathrm{g}100\mathrm{m}{\mathrm{L}}^{\mathrm{‐}1}\right)=\mathrm{‐}0.0458\mathrm{*}\mathrm{A}663+0.204\mathrm{*}\mathrm{A}645+0.372\mathrm{A}505–0.0806\mathrm{A}453.$$
$$\mathrm{{\rm B}}\mathrm{‐}\mathrm{C}\mathrm{a}\mathrm{r}\mathrm{o}\mathrm{t}\mathrm{e}\mathrm{n}\mathrm{e}(\mathrm{m}\mathrm{g}100\mathrm{m}{\mathrm{L}}^{\mathrm{‐}1})=0.216\mathrm{*}\mathrm{A}663-1.22\mathrm{*}\mathrm{A}645–0.304\mathrm{A}505–0.452\mathrm{A}453.$$