Henley W J, Lindley S T, Levavasseur G, Osmond C B, Ramus J
Duke University Marine Laboratory, 28516, Beaufort, NC, USA.
Department of Botany, Duke University, 27706, Durham, NC, USA.
Oecologia. 1992 Apr;89(4):516-523. doi: 10.1007/BF00317158.
We have investigated the diurnal response of photosynthesis and variable photosystem II (PSII) chlorophyll fluorescence at 77 K for thalli of the chlorophyte macroalga, Ulva rotundata, grown in outdoor culture and transplanted to an intertidal sand flat in different seasons. The physiological response in summer indicated synergistic effects of high PFD and aerial exposure, the latter probably attributable to temperature, which usually increased by 8 to 10° C during midday emersion. Except at extreme emersed temperatures in summer (38° C), the light-saturated photosynthesis rate (P) did not decline at midday. In contrast, light-limited quantum yield of photosynthetic O exchange (τ) and the ratio of variable to maximum fluorescence yield (F/F) reversibly declined during midday low tides in all seasons. Shade-grown thalli exhibited a fluorescence response suggestive of greater photodamage to PSII, whereas sun-grown thalli had greater photoprotective capacity. The fluorescence decline was smaller when high tide occurred at midday, and was delayed during morning cloudiness. These results suggest that the diurnal response to PFD in this shallow water species is modified by tidal and meteorological factors. U. rotundata has a great capacity for photoprotection which allows it to tolerate and even thrive in the harsh intertidal environment.
我们研究了室外培养并在不同季节移植到潮间带沙滩的绿藻大型海藻圆石莼叶状体光合作用和77K下可变光系统II（PSII）叶绿素荧光的日变化响应。夏季的生理响应表明高光通量密度（PFD）和暴露于空气中具有协同效应，后者可能归因于温度，在中午退潮期间温度通常会升高8至10摄氏度。除了夏季极端退潮温度（38摄氏度）外，中午时光饱和光合作用速率（P）并未下降。相反，在所有季节的中午低潮期间，光合氧交换的光限制量子产率（τ）以及可变荧光与最大荧光产率之比（F/F）会可逆性下降。在遮荫条件下生长的叶状体表现出对PSII光损伤更大的荧光响应，而在阳光下生长的叶状体具有更强的光保护能力。当中午涨潮时，荧光下降幅度较小，并且在早晨多云时会延迟。这些结果表明，潮汐和气象因素改变了这种浅水物种对PFD的日变化响应。圆石莼具有很强的光保护能力，这使其能够在恶劣的潮间带环境中耐受甚至茁壮成长。
