caa a22 4500 469096934 CHVBK 20180323133033.0 cr unu---uuuuu 170328e19920401xx s 000 0 eng 10.1007/BF00317158 doi (NATIONALLICENCE)springer-10.1007/BF00317158 Photosynthetic response of Ulva rotundata to light and temperature during emersion on an intertidal sand flat [Elektronische Daten] [W. Henley, S. Lindley, G. Levavasseur, C. Osmond, J. Ramus] Summary: 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 (Pm) did not decline at midday. In contrast, light-limited quantum yield of photosynthetic O2 exchange (τ) and the ratio of variable to maximum fluorescence yield (Fv/Fm) 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. Springer-Verlag, 1992 Chlorophyll fluorescence nationallicence Photoinhibition nationallicence Photosynthesis nationallicence Temperature stress nationallicence Ulva nationallicence Fo : instantaneous yield of chlorophyll fluorescence nationallicence Fm : maximum yield of fluorescence nationallicence Fv : variable yield (Fm−Fo) of fluorescence nationallicence PFD : photon flux density (400-700 nm) nationallicence Pm : light-saturated rate of photosynthesis nationallicence PSH : photosystem II nationallicence QA : electron acceptor of PSII nationallicence τ : light-limited quantum yield of photosynthesis nationallicence Henley W. Duke University Marine Laboratory, 28516, Beaufort, NC, USA aut Lindley S. Duke University Marine Laboratory, 28516, Beaufort, NC, USA aut Levavasseur G. Duke University Marine Laboratory, 28516, Beaufort, NC, USA aut Osmond C. Department of Botany, Duke University, 27706, Durham, NC, USA aut Ramus J. Duke University Marine Laboratory, 28516, Beaufort, NC, USA aut Oecologia Springer-Verlag 89/4(1992-04-01), 516-523 0029-8549 89:4<516 1992 89 442 https://doi.org/10.1007/BF00317158 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00317158 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Henley W. Duke University Marine Laboratory, 28516, Beaufort, NC, USA aut NATIONALLICENCE 700 1- Lindley S. Duke University Marine Laboratory, 28516, Beaufort, NC, USA aut NATIONALLICENCE 700 1- Levavasseur G. Duke University Marine Laboratory, 28516, Beaufort, NC, USA aut NATIONALLICENCE 700 1- Osmond C. Department of Botany, Duke University, 27706, Durham, NC, USA aut NATIONALLICENCE 700 1- Ramus J. Duke University Marine Laboratory, 28516, Beaufort, NC, USA aut NATIONALLICENCE 773 0- Oecologia Springer-Verlag 89/4(1992-04-01), 516-523 0029-8549 89:4<516 1992 89 442 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer