Physiological Traits of Kiwifruit Leaves

The phenolics, flavonoids, soluble protein, malonaldehyde (MDA), resistance enzyme activities and photosynthetic characteristics of kiwifruit leaves were determined on 25 August 2021. Total phenolics and total flavonoids were determined using an UV-5800PC spectrophotometer at 280 nm (OD₂₈₀) and 325 nm (OD₃₂₅) with 20 mL 1% (v/v) HCl-methyl alcohol at 3 °C for 1 h without light extraction [32 (link)]. The soluble protein, MDA, catalase (CAT), peroxidase (POD), polyphenoloxidase (PPO) and superoxide dismutase (SOD) activities of kiwifruit leaves were determined as described by Zhang et al. [33 (link)]. The chlorophyll content of kiwifruit leaves was measured using an UV-5800PC spectrophotometer at 645 nm (OD₆₄₅) and 663 nm (OD₆₆₃) with an acetone–ethanol (v/v, 2:1) extraction. A portable LI-6400XT photosynthesis measurement system (LI-COR Inc., Lincoln, NE, USA) was used for monitoring the photosynthetic rate (Pn) and transpiration rate (Tr) of kiwifruit leaves at 8:00–10:00 a.m. on 25 August 2021. Water use efficiency (WUE) of kiwifruit was Pn/Tr.