Action of near UV and blue light on the photocontrol of phycobiliprotein formation; a complementary chromatic adaptation.

Action of near UV to blue light on photocontrol of phycoerythrin (PE) and phycocyanin (PC) formation was investigated with non-photobleached Tolypothrix tenuis and Fremyella diplosiphon; this study was done to evaluate the proposition of Haury and Bogorad [(1977) Plant Physiol., 60: 835] that near UV to blue light is as effective as green and red light for photocontrol of PE and PC formation in blue-green algae and that lack of the blue effect in previous experiments was due to destruction of blue-absorbing pigment(s) by the photobleaching treatment involved in the experimental method. In our present work, light effect was measured in heterotrophic cultures incubated in darkness following brief exposure to different wavelengths of light. Results indicated that (1) near UV to blue light was not effective for induction of PE formation either in T. tenuis or in F. diplosiphon, and (2) PC formation was induced by near UV light at 360 nm but not by blue light at 460 nm. These features are identical with those previously reported for photobleached cells but not with those reported by Haury and Bogorad for non-photobleached cells. We conclude that photobleaching treatment does not have any influence on the action of near UV to blue light. Action at 390 and 460 nm observed by Haury and Bogorad probably resulted from light effects other than photocontrol, e.g., the action of photosynthesis

Diversity of phlorotannin profiles among sargassasacean species affecting variation and abundance of epiphytes

<p>In general, epiphytes have detrimental effects on the growth of their basiphytes due to competition for light and nutrients. Therefore, basiphyte species must expend energy suppressing epiphytes. Some studies suggest that phlorotannins, i.e. brown algal polyphenols, prevent colonization by epiphytes, whereas others question their allelopathic function because there is not necessarily a negative correlation between epiphyte abundance and the phlorotannin content of the basiphyte algae. Various phlorotannin components are found in brown algal species, thus we hypothesized that the antifouling activities of polyphenolic compounds may differ and that the analysis of phlorotannin profiles could be useful for estimating their ecological functions. We surveyed the epiphyte richness in the apical portions of 373 thalli from 15 sargassacean species, demonstrating that the variation and abundance of epiphyte species differed remarkably among the basiphyte species. However, there was a weak negative correlation between the density and total phlorotannin content of the basiphyte algae in only one of the 18 epiphyte species. The interspecific differences in the phlorotannin profile were characterized by quantitative ¹H nuclear magnetic resonance spectroscopy (qNMR), and four major groups were categorized based on cluster and principal component analyses of polyphenolic signals in the qNMR spectra. The epiphyte <i>Neosiphonia harveyi</i> was more abundant on <i>Sargassum hemiphyllum, S. patens</i> and <i>S. piluliferum</i> than on other basiphyte species, and these three species were similar according to the cluster analysis. These results suggest that some phlorotannin components may be more effective for antifouling; thus interspecific differences in the phlorotannin profile could affect the variation and abundance of epiphytes.</p

Effects of Silicon-Limitation on Growth and Morphology of <i>Triparma laevis</i> NIES-2565 (Parmales, Heterokontophyta)

<div><p>The order Parmales (Heterokontophyta) is a group of small-sized unicellular marine phytoplankton, which is distributed widely from tropical to polar waters. The cells of Parmales are surrounded by a distinctive cell wall, which consists of several siliceous plates fitting edge to edge. Phylogenetic and morphological analyses suggest that Parmales is one of the key organisms for elucidating the evolutionary origin of Bacillariophyceae (diatoms), the most successful heterokontophyta. The effects of silicon-limitation on growth and morphogenesis of plates were studied using a strain of <i>Triparma laevis</i> NIES-2565, which was cultured for the first time in artificial sea water. The cells of <i>T. laevis</i> were surrounded by eight plates when grown with sufficient silicon. However, plate formation became incomplete when cells were cultured in a medium containing low silicate (ca. <10 µM). Cells finally lost almost all plates in a medium containing silicate concentrations lower than ca. 1 µM. However, silicon-limitation did not affect growth rate; cells continued to divide without changing their growth rate, even after all plates were lost. Loss of plates was reversible; when cells without plates were transferred to a medium containing sufficient silicate, regeneration of shield and ventral plates was followed by the formation of girdle and triradiate plates. The results indicate that the response to silicon-limitation of <i>T. laevis</i> is different from that of diatoms, where cell division becomes inhibited under such conditions.</p></div