利用调制叶绿素荧光仪研究了宝山堇菜（Viola baoshanensis）和紫花地丁(V. yedoensis)叶片叶绿素荧光参数的日变化.Y值与温度和光合有效辐射的变化趋势相反. 紫花地丁NPQ呈单峰型增长，宝山堇菜NPQ有先增加，后下降的趋势，变化幅度相对紫花地丁平缓.2种堇菜rETR首先迅速上升，维持在一个较高水平，然后迅速下降，Ik变化趋势相对一致.紫花地丁Pm和 呈双峰型变化，宝山堇菜有先增加，后下降的变化趋势.相关性显示，宝山堇菜叶片叶绿素荧光参数与温度和光合有效辐射相关程度低，仅叶片rETR与光合有效辐射呈显著正相关（p 0.05）. 紫花地丁叶片温度分别与Y、NPQ呈显著负相关和正相关（p 0.05），叶表光合有效辐射与Y、NPQ分别达极显著负相关和正相关（p 0.01），与rETR显著正相关（p 0.05）.结果表明，正午时刻两种堇菜光系统Ⅱ遭受了光抑制，温度和光合有效辐射是引起紫花地丁光抑制的重要因素，热耗散和光呼吸是紫花地丁的重要光保护机制，宝山堇菜通过光呼吸来保护光合机构.
Diurnal dynamics of photosynthetic parameters of Viola baoshanensis and V. yedoensis were investigated based on pulse amplitude modulated (PAM). Y (Effective quantum yield) of the two species decreased at midday, indicating that photoinhibition occurred. ETR (electron transport rate) of the two species increased very quickly in morning, and kept at a high level, then decreased. There were difference variation patterns between the two viola species for NPQ， rETR，Pm， Ik and ， and few significant relationships between leaf temperature, PAR and Chlorophyll fluorescence parameters for V. baoshanensis except between PAR and rETR. For V. yedoensi, the significant negative relationships were found between leaf temperature, PAR and Y, significant positive relationships between leaf temperature, PAR and NPQ, and a significant positive relationship between PAR and NPQ. The above results showed that excess light energy dissipated via the xanthophyll cycle and large proportion of electrons allocated to photorespiration for V. yedoensi played roles in protecting the photosynthetic apparatuses. For V. baoshanensis, preventing photodamage was mainly through large proportion of electrons allocated to photorespiration.