“…The sugars in tomato (Sung et al, 2015), rice (Khan et al, 2021), stevia (Sun et al, 2021), and corn (Ma et al, 2020), as the main form of photosynthetic products, all had significant changes under stress. Polyphenol oxidase (PPO), which is widely present in animals and plants, was a key enzyme determining the color of mammalian skin, hair, fruits and vegetables, and food softening (Kim et al, 2005;Ren et al, 2021). It was reported by Kunito, T., et al that PPO promoted the degradation of cellulose and lignin in the soil, and its activity decreased with the increase of N (Kunito et al, 2009), which was of importance for the study of stem strength.…”