Larkum, AWD & Wood, WF 1993, 'The effect of UV-B radiation on photosynthesis and respiration of phytoplankton, benthic macroalgae and seagrasses', Photosynthesis Research, vol. 36, no. 1, pp. 17-23.
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Several species of marine benthic algae, four species of phytoplankton and two species of seagrass have been subjected to ultraviolet B irradiation for varying lengths of time and the effects on respiration, photosynthesis and fluorescence rise kinetics studied. No effect on respiration was found. Photosynthesis was inhibited to a variable degree in all groups of plants after irradiation over periods of up to 1 h and variable fluorescence was also inhibited in a similar way. The most sensitive plants were phytoplankton and deep-water benthic algae. Intertidal benthic algae were the least sensitive to UV-B irradiation and this may be related to adaptation, through the accumulation of UV-B screening compounds, to high light/high UV-B levels. Inhibition of variable fluorescence (Fv) of the fluorescence rise curve was a fast and sensitive indicator of UV-B damage. Two plants studied, a brown alga and a seagrass, showed very poor recovery of Fv over a period of 32 h. © 1993 Kluwer Academic Publishers.
Lockhart, PJ, Penny, D, Hendy, MD & Larkum, ADW 1993, 'IsProchlorothrix hollandica the best choice as a prokaryotic model for higher plant Chla/b photosynthesis?', Photosynthesis Research, vol. 37, no. 1, pp. 61-68.
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We examine the issue of prochlorophyte origins and provide analyses which highlight the limitations of inferring evolutionary trees from anciently diverged sequences that have markedly different GC contents. Under these conditions we have found that current tree reconstruction methods strongly group together sequences with similar GC contents, whether or not the sequences share a common ancestor. We provide 3′psbA termini sequence for Prochloron didemni and find it does not have the 7 amino acid deletion that occurs in Chl a/b chloroplasts and Prochlorothrix hollandica. This is consistent with the recent findings of a Chl c like pigment in the light harvesting system in other prochlorophytes but apparently absent in P. hollandica. From these observations we suggest that P. hollandica is the prochlorophyte most closely related to Chl a/b containing chloroplasts and hence the most appropriate prokaryotic model for higher plant Chl a/b photosynthesis. © 1993 Kluwer Academic Publishers.
Post, A & Larkum, AWD 1993, 'UV-absorbing pigments, photosynthesis and UV exposure in Antarctica: comparison of terrestrial and marine algae', Aquatic Botany, vol. 45, no. 2-3, pp. 231-243.
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Since Antarctic plants experience a wide range of ultraviolet (UV) exposure, the pigment content of Antarctic algae (Palmaria decipiens (Reinsch) Ricker, Enteromorpha bulbosa (Suhr) Montagne, Prasiola crispa (Lightf.) Kütz. sp. antarctica (Kützing) Knebel) was monitored over a year. In summer the mature form of the marine rhodophyte Palmaria contains a range of UV-absorbing pigments in high concentration providing a broad absorbance with a maximum at 337 nm. Juvenile fronds develop through winter with smaller absorbance maxima at 322 nm, 309 nm and 295 nm. The terrestrial chlorophyte Prasiola crispa contains a single UV-absorbing pigment with a maximum at 325 nm. Compared with other green algae, including the marine Enteromorpha, the UV-absorbing pigment in Prasiola is present in high concentrations. Variations in the level of UV-absorbance relative to chlorophyll in Prasiola, appear to correspond with varying UV exposure. To test this, Prasiola was maintained with an enhanced ratio of UV-B to visible light to simulate the effects of stratospheric ozone depletion. After 4 weeks the chlorophyll content and photosynthetic rates were reduced in the presence of enhanced UV-B light, but the ratio of UV-absorbing pigments to chlorophyll was unchanged. This suggests that even for Antarctic algae, that contain high levels of UV-absorbing pigments, exposure to sunlight with an increased ratio of UV-B to visible light is stressful. © 1993.
