Photoacclimation and photoinhibition in Ulva rotundata as influenced by nitrogen availability

Journal Article

Clonal tissue of the marine chlorophyte macroalga, Ulva rotundata Blid., was transferred from 100 to 1700 μmol photons · m-2 · s-1 under limiting (1.5 μM NH4+maximum, N/P=2) and sufficient (15 μM NH4+maximum, N/P=20) nitrogen supply at 18° C and 11 h light-13 h darkness daily. Photoinhibition was assayed by light-response curves (photosynthetic O2 exchange), and chlorophyll fluorescence at 77 K and room temperature. Daily surface-area growth rate (μSA) in N-sufficient plants increased sixfold over 3 d and was sustained at that level. During this period, respiration (Rd) doubled and light-saturated net photosynthesis capacity (Pm) increased by nearly 50%, indicating acclimation to high light. Quantum yield (φ{symbol}) decreased by 25% on the first day, but recovered completely within one week. The ratio of variable to maximum fluorescence (Fv/Fm) also decreased markedly on the first day, because of an increase in initial fluorescence (Fo) and a decrease in Fm, and partially recovered over several days. Under the added stress of N deficiency, μSA accelerated fivefold over 4 d, despite chronic photoinhibition, then declined along with tissue-N. Respiration doubled, but Pm decreased by 50% over one week, indicating inability to acclimate to high light. Both φ{symbol} and Fv/Fm decreased markedly on the first day and did not significantly recover. Changes in Fo, Fm and xanthophyll-cycle components indicate concurrent photodamage to photosystem II (PSII) and photoprotection by thermal deexcitation in the antenna pigments. Increasing μSA coincided with photoinhibition of PSII. Insufficient diel-carbon balance because of elevated Rd and declining Pm and tissue-N, rather than photochemical damage per se, was the apparent proximate cause of decelerating growth rate and subsequent tissue degeneration under N deficiency in U. rotundata. © 1991 Springer-Verlag.

Full Text

Duke Authors

Cited Authors

  • Henley, WJ; Levavasseur, G; Franklin, LA; Osmond, CB; Ramus, J

Published Date

  • 1991

Published In

Volume / Issue

  • 184 / 2

Start / End Page

  • 235 - 243

International Standard Serial Number (ISSN)

  • 0032-0935

Digital Object Identifier (DOI)

  • 10.1007/BF00197952