Abstract: 【Objective】To investigate the effects of different shading conditions on the photosynthetic characteristics of leaves in the variegated mutant of Heliopsis helianthoides,thereby providing a reference for its cultivation and application. 【Methods】Using the variegated mutant HY-23F₁-2 of H. helianthoides as the experimental material,three treatments were established：30% shading,50% shading,and 70% shading. The effects of different treatments on chlorophyll content,diurnal variations in photosynthetic physiological indices,photosynthetic light-response curves,and light-response parameters in the leaves of the variegated mutant of H. helianthoides were analyzed.【Results】Under the 50% shading treatment,the contents of total chlorophyll（Chlt）,chlorophyll a（Chla）,and chlorophyll b（Chlb） in the leaves of the variegated mutant HY-23F₁-2 of H. helianthoides were significantly higher than those under the 30% and 70% shading treatments（P<0.05）. The diurnal variations in net photosynthetic rate（P_n）,stomatal conductance（G_s）,and transpiration rate（E） all exhibited a bimodal pattern,with the highest average values of 8.79 μmol/（m²·s）,0.37 mmol/（m²·s）,and 6.62 mmol/（m²·s）,respectively. The diurnal variation in intercellular CO₂ concentration（C_i）showed a serrated pattern,with the lowest average value of 322.17 μmol/mol. The maximum net photosynthetic rate（P_nmax）and light saturation point（LSP）were the highest,at 14.50 and 1 802.74 μmol/（m²·s）,respectively. Under the 70% shading treatment,the contents of Chlt,Chla,and Chlb were the lowest. The diurnal variation in P_n displayed a unimodal pattern,with the lowest average value of 4.63 μmol/（m²·s）. The diurnal variation in C_i presented a W curve trend,with the highest average value of 342.97 μmol/mol. The apparent quantum yield（AQY） was the highest at 0.047 0 μmol/mol,while P_nmax,LSP,light compensation point（LCP）,and dark respiration rate（Rd）were the lowest. Correlation analysis revealed extremely significant negative correlation between P_n and C_i（P<0.01）.【Conclusion】The 50% shading treatment is more suitable for the growth of the variegated mutant HY-23F₁-2 of H. helianthoides,and under the 70% shading treatment,the variegated mutant HY-23F₁-2 of H. helianthoides exhibits stronger shade tolerance and photosynthetic potential.

Key words: Variegated mutant of Heliopsis helianthoides, Chlorophyll content, Diurnal variations in photosynthetic physiological indices, Light-response parameters