Abstract: To explore the effects of chitosan-modified biochar originated from Platanus orientalis L. leaves on physiological characteristics of rapeseed under cadmium-contaminated soil, a pot experiment with five different treatments of CK, Cd, chitosan+Cd (K+Cd), biochar+Cd (C+Cd), chitosan-modified biochar+Cd (Kc+Cd) was conducted. The results showed that the applications of chitosan, biochar, chitosan-modified biochar all had positive impacts on antioxidant system (POD, CAT, SOD) and osmotic regulatory substances (malondialdehyde (MDA), proline (Pro), soluble sugar and soluble protein) in rapeseed subjected to cadmium stress. Under the Kc+Cd treatment, the SOD activity of rapeseed reduced by 28.1% compared with Cd treatment; the soluble sugar and soluble protein content significantly increased by 187.7% and 32.7%, respectively (P<0.05); the chlorophyll synthesis was effectively enhanced, light saturation point (L_SP), light compensation point (L_CP), apparent quantum efficiency (A_QY), maximum net photosynthetic rate (P_max) and dark respiration rate (R_d) were significantly increased. Maximum fluorescence (F_m), variable fluorescence (F_v), maximum photochemical efficiency of PSⅡ (F_v/F_m), electron transport efficiency (ETR), actual photochemical efficiency (YⅡ), and photochemical quenching coefficient (qP) were increased. Chitosan, biochar, and chitosan-modified biochar alleviated the oxidative stress of rape induced by heavy metals, promoted rape growth, and had positive effects on the photosynthetic characteristics and fluorescence characteristics of rape under cadmium stress, with the chitosan-modified biochar performing the best.

Key words: garden waste biochar, rape, cadmium, physiological characteristics