Ceramium brevizonatum var. caraibica Peter. et Børg., Dasya corymbifera J. Ag., Dudresnaya hawaiiensis R.K.S. Lee, Chrysymenia agardhii Harv. and Hypnea boergesenii Tanaka are recorded and described for the first time from the St. Martin's Island, Cox's Bazar, Bangladesh. Key words: Seaweeds; Red algae; Dudresnaya hawaiiensis; St. Martin's Island; Bangladesh DOI: 10.3329/bjb.v39i1.5531Bangladesh J. Bot. 39(1): 87-96, 2010 (June)

Abiotic and biotic stresses widely reduce light harvesting complex (LHC) gene expression in higher plants and algae. However, control mechanisms and functions of these changes are not well understood. During herbivory, marine diatom species release oxylipins that impair grazer reproduction and serve as signaling molecules to nearby undamaged diatoms. to examine LHC mRnA regulation by oxylipin exposure, the diatom Phaeodactylum tricornutum was treated with a sublethal concentration of trans,trans-2,4-decadienal (DD) during the light cycle. Transcriptome analyses revealed extensive suppression of LHC mRnAs and a smaller set of up-regulated LHC mRNAs at 3 h. For two divergently regulated LHCF antennae family mRnAs, in vivo 4-thiouracil metabolic labeling was used to distinguish synthesis and degradation rates. Within 3 h of DD exposure, Lhcf2 mRnA levels and transcription were strongly suppressed and its mRnA half-life decreased. in contrast, Lhcf15 mRnA mainly accumulated between 3-9 h, its transcription increased and its mRNA was highly stabilized. Hence, DD-treated cells utilized transcriptional and mRnA stability control mechanisms which were likely major factors in the differing Lhcf2 and Lhcf15 expression patterns. Widespread LHC mRnA regulation and possible effects on photosynthesis may contribute to enhanced fitness in cells impacted by herbivory and other stresses. In photosynthetic eukaryotes, photosynthetic processes are regulated by extensive internal and external inputs in both unperturbed and stress conditions 1,2. For example, exposures to high light, nutrient deprivation and herbivory promote mechanisms postulated or demonstrated to maintain homeostasis in photosynthesis 3. Central to the light reactions are the families of light harvesting complex (LHC) proteins which primarily function to efficiently deliver light energy to photosystem core components 4,5. Of relevance to this study, a major and widespread gene regulation response to biotic and abiotic stresses in plants including microalgae is a period of extensive repression of LHC mRNAs coupled with upregulation of a smaller set of LHC mRNAs 6-8. The functional significance of these changes and the regulatory mechanisms that control them are poorly understood 6,9. Genes affecting protective light reaction traits, including specific LHC genes, represent attractive targets for crop improvement to mitigate adverse stress effects. In tobacco, genetic engineering of photoprotection mechanisms resulted in an accelerated recovery phase from high light stress and a 15% increase in biomass 10. Study of photosynthetic acclimation mechanisms in marine diatoms can provide insights for this ecologically and evolutionarily important taxonomic group but also for higher plants and other algal lineages. Diatoms are widely dispersed throughout ocean ecosystems, face rapidly changing conditions and yet are highly competitive and efficient as a dominant phytoplankton group. They contribute almost 40% of marine primary productivity and about 20% of global carbon fix...

Acrochaetium nurulislamii sp. nov. and Acrochaetium polysporum Howe, A. sagraeanum (Montagne) Bornet and A. zosterae Papenfuss are recorded and described for the first time from the St. Martin's Island, Cox's Bazar, Bangladesh.

Cladophora crispula Vickers, Cladophora prolifera (Roth) Kütz. and Phyllodictyon anastomosans (Harv.) Kraft et Wynne are recorded and described for the first time from the St. Martin's Island, Cox's Bazar, Bangladesh.

The paper records 6 species of phytoplankton under the class Chlorophyceae namely, Pteromonas golenkiniana Pascher belonging to Family Phacotaceae; Pediastrum biradiatum var. biradiatum Meyen.belonging to Family Hydrodictyaceae; Scenedesmus alternas var. indicus Hortob. and Scenedesmus quadricauda var. inermis Playfair belonging to Family Scenedesmaceae ; Teilingia excavata (Rafls) Bourelly and Cosmarium vexatum W. West var. vexatum W. West belonging to Family Desmidaceae from Sylhet Division of Bangladesh which are all new records for Bangladesh. Bangladesh J. Plant Taxon. 27(1): 79-83, 2020 (June)