National Committee on Marine Sciences (NCMS)
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- Seasonal variations in the yield, gelling properties, and chemical composition of agars from Gracilaria eucheumoides and Gelidiella acerosa (Rhodophyta) from the PhilippinesVillanueva, R. D.; Montaño, N. E.; Romero, J. B.; Aliganga, A. K. A.; Enriquez, E. P. (Walter de Gruyter GmbH, 1999-01-01)The yield, physical, and chemical properties of agars from two Philippine red seaweeds, Gracilaria eucheumoides and Gelidiella acerosa, were investigated on a bimonthly basis. The yield of agar from Gracilaria eucheumoides was at a maximum during the early rainy season (May, 29%) and at a minimum during the summer month of March (20%). In Gelidiella acerosa, a peak in agar yield was also recorded in May (21%), with generally higher yields recorded during the rainy than in the dry season. Agar gel strengths fluctuated from 225 to 430 g cm−2 and from 160 to 820 g cm−2 for Gracilaria eucheumoides and Gelidiella acerosa, respectively, and both agars exhibited strongest gels in July. Significant seasonal variations were observed in the gelling and melting temperatures of agar from Gracilaria eucheumoides, but not from Gelidiella acerosa. Sulphate content only varied slightly in agar samples from Gracilaria eucheumoides, while a higher sulphate content was found in Gelidiella acerosa agar during the dry season. Moreover, the sulphate content in G. acerosa agar fluctuated inversely with the 3,6-anhydrogalactose content. A FT-IR analysis showed a fairly constant spectrum for temporal Gracilaria eucheumoides agar while peaks attributed to S–O vibrations intensified in Gelidiella acerosa samples which were recorded to contain high sulphate residues and possess low gel strengths. Diagnosis of the FT-IR spectra in the 1000–400 cm−1 frequency range was also conducted in comparison with agarose and Gracilaria chilensis agar.
- Karyology and agar analysis of the agarophyte Gelidiella acerosa (Forsskål) Feldmannet Hamel from the PhilippinesKapraun, Donald F.; Ganzon-Fortes, Edna; Bird, Kimon T.; Trono, Gavino; Breden, Chris (Springer, 1994-12)Microspectrophotometry with the DNA-localizing fluorochrome DAPI demonstrated ploidy level differences in tetrasporophytic and presumptive gametophytic phases of Gelidiella acerosa from the Philippines. Comparison of mean nuclear DNA (I f ) values to chicken erythrocytes (RBC) resulted in an estimate of 0.32 pg/2 C genome. Karyological studies with aceto-orcein revealed a chromosome complement of six bivalents during diakinesis of tetrasporocytes. The agar yield ranges from 13–24% dry weight, depending on the method of extraction. Agar extraction in 1 N NaOH resulted in an increased gel strength of 189 g cm−2 at 1.5% concentration. Infrared spectroscopy indicated a relatively high sulfate content in native agar. The low (61 °) melting temperature is indicative of high sulfation and small molecular size.
- Diurnal and diel patterns in the photosynthetic performance of the agarophyte Gelidiella acerosaGanzon-Fortes, E. T. (Walter de Gruyter, 1997)Photosynthesis of the red alga Gelidiella acerosa was monitored on diurnal (during the day) and diel (24 h period) bases using the oxygen evolution technique in a closed system. Natural sunlight and artificial light were used to assess uniformity in the diurnal photosynthetic responses. Photosynthesis-irradiance (P-I) curves were also determined diurnally. On a diel basis, maximal photosynthetic rates occurred at day time and minimal rates occurred at night. Diurnally, photosynthesis fluctuated in different patterns depending on PFDs used. Under saturating but not photoinhibiting FFDs, photosynthesis exhibited an early morning minimum (a few hours after sunrise), a midday-noon maximum, sustained until late afternoon, then declined at or after sunset. However, when exposure to high PFDs (above 1200 μιηοΐ photons m"~s") were prolonged, i.e. from morning until afternoon, the photosynthetic performance suffered a depression starting from noon and persisting until afternoon. When PFDs lowered late in the afternoon, recovery of photosynthetic performance commenced resulting in increased photosynthetic rates. The P-I curve data corroborate findings of experiments using saturating but not photoinhibiting PFDs. The morning P-I curve had lower Pm and alpha, and higher Ik and Is values than the identical noon and afternoon P-I curves. This suggested that photosynthetic performance was yet inefficient in the morning but performed efficiently near midday until the afternoon. An endogenous circadian clock was implicated to have influenced the diurnal and diel patterns in the photosynthetic performance of G. acerosa. Photoinhibition was the other factor suspected to have altered the diurnal pattern.