Abstract: Saccharum officinarum L. cv. Badila seedlings were used to study the effect of longtime chill acclimation (12 ℃/8 ℃ for 28 days) on the light use efficiency in photosynthesis. The results showed that chill acclimation decreased the net photosynthetic rate but increased the dark respiration rate (R_d) and the ratio of PSII operating efficiency to CO₂ assimilation efficiency (Φ_PSII/Φ_CO2) compared with the seedlings grown at 25 ℃/20 ℃ (control) regardless at ambient temperature (25 ℃) or at low temperature (12 ℃). The measurement under ambient temperature showed the chill acclimation decreased the declining rate of F_v′/F_m′ (changing reversely to NPQ) declining with Φ_PSII while increased the declining rate of photochemical quenching (q_P) declining with Φ_PSII at different light intensities. The measurements at low temperature, however, showed no significant differences in the declining rates of F_v′/F_m′ and q_P declining with Φ_PSII compared with the control. It was indicated that the longtime chill acclimation treatment dissipated the excessive light energy through both nonphotochemical and photochemical quenching pathways, thus improved its photosynthetic sensitivity to chill. The present study provides important references for chillingresistant breeding and cultivation of chewing cane.

Key words: forest type, soil available N, litterfall, Chinese fir, soil nitrogen transformation rate