Fig. 3

Proline, γ-aminobutyric acid (GABA), and pyrroline-5-carboxylic acid (P5C) contents in leaves of rice under two light treatments and four Zn application levels in 2019 to 2021. Zn0, Zn1, Zn2 and Zn3 mean 0 kg Zn ha^− 1, 1 kg Zn ha^− 1, 2 kg Zn ha^− 1, and 3 kg Zn ha^− 1 applied at booting stage, respectively. NL and LL mean normal light and low light, respectively. Different lowercase letters indicate statistical differences among treatments at P < 0.05