采用双因素完全随机区组试验，设置自然降水量(W)为对照，降水量减少40%(W-)和降水量增加40%(W+)为处理；设置自然降水间隔时间(T)为对照，延长降水间隔时间(T+)为处理。分析降水量和降水间隔时间对树番茄〔Cyphomandra betacea (Cav.) Sendth.〕幼苗的株高、地径、干质量、叶绿素含量、光合参数和荧光参数的影响。结果显示：增加降水量，树番茄幼苗株高、地径的增长量均增加，根、茎、叶的干质量和总干质量基本上均在自然降水量处理下积累最多，且延长降水间隔时间后，幼苗株高、地径的增长量基本上均有所增加。同一降水间隔时间处理下，叶片叶绿素a、叶绿素b和总叶绿素的含量在自然降水量处理下最大，自然降水间隔时间处理下叶绿素a含量与叶绿素b含量的比值(Chla/Chlb)较大。增加降水量，叶片净光合速率(Pn)、气孔导度(Gs)、胞间CO2浓度(Ci)和蒸腾速率(Tr)均升高。增加降水量，初始荧光(Fo)降低，最大荧光(Fm)、可变荧光(Fv)、PSⅡ最大光化学效率(Fv/Fm)、PSⅡ潜在活性(Fv/Fo)增加，且Fm、Fv、Fv/Fm、Fv/Fo值在增加降水量、延长降水间隔时间处理保持较高水平。相关性和主成分分析结果显示：树番茄幼苗大部分生长和光合荧光参数间有显著（P<0.05）或极显著（P<0.01）相关性，Chla/Chlb和Fo值与其他参数均具有负相关关系，除Chla/Chlb和Fo值外，其他参数间均具有正相关关系。综合研究结果表明：树番茄幼苗在不同降水量和降水间隔时间下进行了一系列适应性调节，树番茄幼苗光合作用与植物生长具有紧密联系，光合作用增强将促进树番茄幼苗生长、干物质积累。增加降水量、延长降水间隔时间有利于树番茄幼苗生长和光合作用，其中增加降水量的影响效果更明显。

  A two-way completely randomized block experiment was employed, natural precipitation (W) was set as the control, and 40% reduction in precipitation (W-) and 40% increase in precipitation (W+) were set as the treatments; natural precipitation interval (T) was set as the control, and extended precipitation interval (T+) was set as the treatment. The effects of precipitation and precipitation interval on the plant height, ground diameter, dry mass, chlorophyll content, photosynthetic parameters, and fluorescence parameters of Cyphomandra betacea (Cav.) Sendth. seedlings were analyzed. The results show that with the increase of precipitation, the increments in plant height and ground diameter of C. betacea seedlings increase, the dry masses of roots, stems, and leaves and total dry mass are the most accumulated under natural precipitation treatment in general, and after extending the precipitation interval, the increments in plant height and ground diameter of the seedlings increase in general. Under the same precipitation interval treatment, the contents of chlorophyll a, chlorophyll b, and total chlorophyll of the leaves are the highest under natural precipitation treatment, and the ratio of chlorophyll a content to chlorophyll b content (Chla/Chlb) is relatively high under natural precipitation interval treatment. With the increase of precipitation, the net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular CO2 concentration (Ci), and transpiration rate (Tr) of the leaves all increase. With the increase of precipitation, the initial fluorescence (Fo) decreases, while the maximum fluorescence (Fm), variable fluorescence (Fv), maximum photochemical efficiency of PSⅡ (Fv/Fm), and potential activity of PSⅡ (Fv/Fo) increase, and the values of Fm, Fv, Fv/Fm, and Fv/Fo remain at relative high levels under increased precipitation and extended precipitation interval treatments. The correlation and principal component analysis results show that there are significant （P<0.05） or extremely significant （P<0.01） correlations between most growth and photosynthetic fluorescence parameters of C. betacea seedlings, Chla/Chlb and Fo values are negatively correlated with the other parameters, while all the other parameters are positively correlated with each other except for Chla/Chlb and Fo values. The comprehensive research results indicate that C. betacea seedlings undergo a series of adaptive adjustments under different precipitation and precipitation intervals, the photosynthesis of C. betacea seedlings is closely associated with plant growth, and enhanced photosynthesis promotes the growth and dry matter accumulation of C. betacea seedlings. Increased precipitation and extended precipitation intervals are beneficial for the growth and photosynthesis of C. betacea seedlings, among which the effect of increased precipitation is more evident.