Fluorescence quenching during photosynthesis and photoinhibition of Ulva rotundata blid.

Abstract

Abstract.The relationships between photoinhibition and photoprotection in high and low-light-grown Ulva were examined by a combination of chlorophyll-fluorescencemonitoring techniques. Tissues were exposed to a computer-controlled sequence of 5-min exposures to red light, followed by 5-min darkness, with stepwise increases in photon flux. Coefficients of chlorophyll fluorescence quenching (1-qe and NPQ) were calculated following a saturating pulse of white light near the end of each 5-min light treatment. Dark-adapted chlorophyll fluorescence parameters (Fo and Fv/FM) were calculated from a saturating pulse at the end of each 5-min dark period. Lowlight-grown Ulva showed consistently higher 1-qp, i.e. higher reduction status of Q (high primary acceptor of photosystem II), and lower capacity for nonphotochemical quenching (NPQ) at saturating light than did highlight-grown plants. Consequently, low-light plants rapidly displayed photoinhibitory damage (increased F0) at light saturation in seawater. Removal of dissolved inorganic carbon from seawater also led to photoinhibitory damage of high-light-grown Ulva at light saturation, and addition of saturating amounts of dissolved inorganic carbon protected low-light-grown plants against photoinhibitory damage. A large part of NPQ was abolished by treatment with 3 mM dithiothreitol and the processes so inhibited were evidently photoprotective, because dithiothreitol treatment accelerated photoinhibitory damage in both low-and high-light-grown Ulva. The extent of photoinhibitory damage in Ulva was exacerbated by treatment with chloramphenicol (1 mM) without much effect on chlorophyll-quenching parameters, evidently because this inhibitor of chloroplast protein synthesis reduced the rate of repair processes.Abbreviations: CAP = chloramphenieol; DIC = dissolved inorganic carbon in seawater (i.e. COz+ HCO3 +CO~ ); DTT= dithiothreitol; 1-qp=reduction status of Q, the primary acceptor of PSII, measured as described; FM, Fo, Fv = dark-adapted maximum, minimum and variable fluorescence, respectively; NPQ=nonphoto-chemical fluorescence quenching, measured as described; PFD= photon flux density Correspondence to: C.B. Osmond; FAX: 61(62)490756

High Photosynthetic Capacity in a Shade-Tolerant Crassulacean Acid Metabolism Plant (Implications for Sunfleck Use, Nonphotochemical Energy Dissipation, and Susceptibility to Photoinhibition)

“…5 ) . It is also considerably higher than the maximum NPQ values of 3 to 4 typically reported for high light grown plants (Bilger andBjorkman, 1990, 1991;Osmond et al, 1993;Ruban et al, 1993;DemmigAdams and Adams, 1994;Bilger et al, 1995;Adams and Demmig-Adams, 1996;Shen et al, 1996). From this literature it is believed that sun-adapted species have a greater maximum potential for nonphotochemical energy dissipation than shade-adapted species when both are grown in high light (Thayer and Bjorkman, 1990;Demmig-Adams and Adams, 1994).…”

Determination of microphytobenthos PSII quantum efficiency and photosynthetic activity by means of variable chlorophyll fluorescence

“…Bilger et al 1995). macroalgae (Osmond et al 1993, Hanelt et al 1994 and unicellular algae , Flameling & Kromkamp 1995, Ibelings et al 1995 and is a process which can b e induced (and relax) very rapidly. On intertidal flats, high PFDs will lead to high rates of photosynthesis.…”

The effect of photoacclimation on the photosynthetic physiology ofUlva curvataandUlva rotundata(Ulvales, Chlorophyta)

“…Photoacclimation experiments have been carried out mainly on terrestrial plants and aquatic unicellular algae (Bj6rkman, I981; Falkowski & LaRoche, 1991). The photosynthetic physiology of Ulva species has been studied previously, as well as growth, pigment content and chemical composition (Duke et al, 1986, I989;Ramus & Venable, 1987;Sand-Jensen, 1988a, b;Henley & Ramus, 1989a~ b;Henley et al, 1991a, b;Levavasseur et al, 1991;Henley, I992;Geertz-Hansen & Sand-Jensen, 1992;Markager & Sand-Jensen, 1992Markager, 1993;Osmond et al, 1993;Franklin, 1994). However, current knowledge of the physiology of key species associated with eutrophication (mostly Ulvales) is limited (EUMAC, 1995).…”