中文摘要：

探讨了太阳紫外辐射对两种N水平条件下羊栖菜藻体光化学特性的影响及其恢复。结果显示，在高的光辐射下羊栖菜藻体的有效光化学效率和相对电子传递速率急剧下降，两种N水平条件下藻体的光化学活性下降趋势一致：在全波长太阳辐射条件（即高的光辐射和紫外辐射同时存在）下它们的下降幅度更大，而N加富条件下羊栖菜藻体的相对电子传递速率要高于对照N水平下生长的藻体，表明N加富的生长条件使得藻体具有更高抵御紫外辐射的能力，这可能是与N加富生长条件下的藻体中含有较高含量的紫外吸收物质和类胡萝卜素有关。在低光恢复过程中，全波长辐射处理藻体的有效光化学效率比可见光辐射处理藻体的恢复要慢（分别为6h和3h可恢复到起始水平）；而相对电子传递速率的恢复能力则比有效光化学效率的恢复能力更弱，需要24h或者更长的时间。

英文摘要：

Physiological properties of photosynthesis were investigated under solar radiation in the marine brown macroalga, Hizikia fusiformis, grown at two different N availabilities. The significant decrease of the effective photosynthetic quantum yield and rETR was found in the thalli when exposed to solar radiation, with the decrease fluctuation being more greater in the thalli treated with full solar radiation （ PAB, i.e. PAR plus UV radiation ） than those treated with solar photosynthetically active radiation （ PAR ）. The decrease trend of the effective photosynthetic quantum yield was the same between the algae grown under normal N level and high N level when the thalli were exposed to PAR or PAB. However, when exposed to PAB, rETR of the thalli grown under high N level was higher than those grown under normal N level, indicating that the algae cultured in high N level exhibited higher capacity of defending UV radiation, which might be related with the high contents of UVAC and carotenoids. During the recover period, the effective photosynthetic quantum yields in the thalli treated with PAB recovered a little slowly compared with the thalli treated with PAR （ they reached the initial levels after 6h and 3h, respectively ）. The rETR of the thalli recovered much more slowly （ at least 24 h） than the effective photosynthetic quantum yields did.