为揭示常绿植物光系统Ⅱ（PSⅡ）和光系统Ⅰ（PSⅠ）功能协同性与植物耐冷性之间的关系，以亚热带地区常绿阔叶植物红叶石楠(Photinia × fraseri Dress)、荷花木兰(Magnolia grandiflora Linn.)和雅榕〔Ficus concinna (Miq.) Miq.〕为材料，分别于秋季和冬季测定了3种植物阳生叶的叶绿素荧光快速光曲线和光诱导曲线，并比较了PSⅡ和PSⅠ对冬季低温响应的差异。结果显示：相较于秋季，冬季红叶石楠的PSⅡ最大光化学效率(Fv/Fm)和P700最大荧光信号(Pm)的降幅基本一致(分别为5.6%和5.5%)，荷花木兰和雅榕的Fv/Fm降幅(分别为52.6%和75.9%)均高于Pm降幅(分别为40.2%和59.9%)。快速光曲线中，冬季红叶石楠和荷花木兰PSⅡ实际光化学量子产量〔Y(Ⅱ)〕和PSⅠ光化学量子产量〔Y(Ⅰ)〕对光照强度的响应较为一致，且2个光合系统在高光强下均能保持一定的光化学功能，红叶石楠Y(Ⅱ)和Y(Ⅰ)明显高于荷花木兰；然而冬季雅榕PSⅡ较PSⅠ对中高光强更敏感。光诱导曲线中，诱导稳定后冬季红叶石楠和荷花木兰Y(Ⅰ)较秋季的降幅分别为36.0%和33.9%，但冬季红叶石楠Y(Ⅱ)降幅(51.7%)明显低于荷花木兰(68.4%)，而冬季雅榕Y(Ⅱ)和Y(Ⅰ)的降幅分别高达93.9%和80.5%。冬季3种植物Y(Ⅰ)下降主要是PSⅠ供体侧限制引起的非光化学能量耗散量子产量〔Y(ND)〕增加所致，且Y(ND)增加与Y(Ⅱ)和光化学猝灭系数(qP)的降低密切相关。冬季低温诱导红叶石楠非光化学猝灭系数(NPQ)和PSⅡ调节性能量耗散的量子产量〔Y(NPQ)〕增加，但导致荷花木兰和雅榕NPQ和Y(NPQ)降低，且对雅榕的影响尤为明显。冬季低温诱导3种植物环式电子传递速率占通过PSⅠ的电子传递速率的比例〔CEF/ETR(Ⅰ)〕增加，其中雅榕增幅最大，红叶石楠增幅最小。综合分析结果表明：3种植物PSⅡ对冬季低温的敏感性高于PSⅠ，PSⅡ光抑制对PSⅠ具有一定保护作用；并且，冬季PSⅡ和PSⅠ的功能协同性越高，光抑制程度越低。红叶石楠通过增强热耗散和环式电子传递防御冬季低温光抑制，荷花木兰的光保护策略是增强环式电子传递并维持一定的热耗散能力；而冬季雅榕热耗散能力大幅下降，环式电子传递增强也不能保护PSⅠ免受低温伤害。

 To reveal the relationship of the functional coordination of photosystem Ⅱ (PSⅡ) and photosystem Ⅰ (PSⅠ) with cold tolerance in evergreen plants, evergreen broadleaved plants Photinia × fraseri Dress, Magnolia grandiflora Linn., and Ficus concinna (Miq.) Miq. in subtropical region were taken as materials, the rapid light curves and light induction curves of chlorophyll fluorescence in sun leaves of the three species were measured in autumn and winter, and the differences in responses of PSⅡ and PSⅠ to winter low temperature were compared. The results show that compared with autumn, the decrements in maximum photochemical efficiency of PSⅡ (Fv/Fm) and maximum fluorescence signal of P700 (Pm) of P. × fraseri in winter are basically consistent (which are 5.6% and 5.5%, respectively), while the decrements in Fv/Fm of M. grandiflora and F. concinna (which are 52.6% and 75.9%, respectively) are greater than those in Pm(which are 40.2% and 59.9%, respectively). In the rapid light curves, the responses of actual photochemical quantum yield of PSⅡ ［Y(Ⅱ)］ and photochemical quantum yield of PSⅠ ［Y(Ⅰ)］ of P. × fraseri and M. grandiflora to light intensity in winter are relatively consistent, and the two photosystems can maintain certain photochemical functions under high light intensity, and the Y(Ⅱ) and Y(Ⅰ) of P. × fraseri are evidently higher than those of M. grandiflora. However, the PSⅡ of F. concinna in winter is more sensitive to moderate and high light intensity than PSⅠ. In the light induction curves, after the light induction stabilized, the decrements in Y(Ⅰ) of P. × fraseri and M. grandiflora in winter are 36.0% and 33.9% respectively compared with autumn, however, the decrement in Y(Ⅱ) of P. × fraseri (51.7%) is significantly lower than that of M. grandiflora (68.4%), whereas the decrements in Y(Ⅱ) and Y(Ⅰ) of F. concinna are as high as 93.9% and 80.5%, respectively. The decline in Y(Ⅰ) of the three species in winter is primarily caused by increases in quantum yield of nonphotochemical energy dissipation in PSⅠ due to donor side limitation ［Y(ND)］, which is closely correlated with the decreases in Y(Ⅱ) and photochemical quenching coefficient (qP). Winter low temperature induces an increase in nonphotochemical quenching coefficient (NPQ) and quantum yield of regulated energy dissipation in PSⅡ ［Y(NPQ)］ of P. × fraseri, but leads to decreases in NPQ and Y(NPQ) of M. grandiflora and F. concinna, and the effect is particularly obvious in F. concinna. Winter low temperature  induces an increase in the proportion of cyclic electron transport rate in the electron transport rate of PSⅠ ［CEF/ETR(Ⅰ)］ in the three species, among which the increment is the greatest in F. concinna, and the smallest in P. × fraseri. The comprehensive analysis result indicates that the sensitivity of PSⅡ to winter low temperature is higher than that of PSⅠ in the three species, and photoinhibition of PSⅡ provides some protection to PSⅠ; moreover, the higher the functional coordination between PSⅡ and PSⅠ in winter, the lower the degree of photoinhibition. P. × fraseri defends against winter low-temperature photoinhibition by enhancing thermal dissipation and cyclic electron flow, whereas the photoprotective strategy of M. grandiflora is to enhance cyclic electron transport and maintaining a certain capacity for thermal dissipation; while the thermal dissipation capacity of F. concinna in winter substantially reduces, and the enhancement of cyclic electron transport could not protect PSⅠ from low-temperature damage.