No abstract

Agar is the most valuable phycocoloid in the world market. Currently, about half of its production is obtained from the red alga Gracilaria (Gracilariales, Rhodophyta). Consequently, this genus has been the subject of many studies worldwide. A common green color variant of G. domingensis (Kützing) Sonder ex Dickie was found in a natural population on the northeastern coast of Brazil. Crosses were performed to determine the mode of color inheritance. The results can be interpreted as the expression of a pair of codominant alleles, where the green and red phenotypes are homozygous, and the heterozygotes present a brownish color. Heterozygous tetrasporophytes, at least until they are 4-5 cm long, exhibit a parental influence on the female gametophyte, since the reddish-brown or greenish-brown color is dependent on the female parent color (red or green). Mixed reproductive phases, as well as specimens with patches of different colors bearing spermatangia or cystocarps, were observed in laboratory cultures. Gametophytes that resulted from in situ germination of meiospores were also observed, and could be easily detected when red or green gametophytes were grown on brown tetrasporophytes.
Dentre os colóides extraídos de algas, o ágar é o mais valioso no mercado mundial, sendo que aproximadamente metade da produção é obtida a partir de algas vermelhas do gênero Gracilaria (Gracilariales, Rhodophyta). Conseqüentemente, o gênero vem sendo alvo de muitos estudos em todo o mundo. Um variante de cor verde de G. domingensis (Kützing) Sonder ex Dickie foi encontrado numa população natural do nordeste da costa do Brasil. Realizaram-se cruzamentos para determinar o modo de herança da cor. Os resultados foram interpretados como a expressão de um par de alelos codominantes, onde os fenótipos de cor verde e vermelha são homozigotos e o heterozigoto apresenta a cor marrom. Tetrasporófitos heterozigotos de até 4-5 cm de comprimento apresentam uma influência do gametófito feminino que lhes deu origem, já que a coloração marrom-avermelhada ou marrom-esverdeada é dependente da cor do gametófito feminino (vermelho ou verde). A ocorrência de diferentes estruturas reprodutoras em um mesmo talo, bem como espécimens com manchas de diferentes cores apresentando cistocarpos ou espermatângios, foi observada em culturas de laboratório. Foi possível constatar a germinação de tetrásporos e conseqüente desenvolvimento de gametófitos in situ, facilmente detectados pela coloração verde ou vermelha sobre tetrasporófitos de coloração marrom

Green. brown and red phenotypes of Graclfaria domingclIsis have been observed growing side by side in natural populations in the northeast of BraZIl. The phycoerythrin:phycocyanin ratio of the three colour types mcreased from green to brown to red phenotypes. The frequency of green mutant individuals was studied during three consecutive years in two natural populations 110 km apart in Ceara State. Brazil. Green variants were found at frequencies of 7% to 19% in both populations showmg that the deficiency in phycoerythrin did not strongly affect the fitness of individuals in these sunny intertidal populations. Moreover. the relative stability of the green allele frequency in space and time suggested that the selective pressures are equivalent in the two sites and/or that the two populations are not genetically isolated.

RESUMO -(Efeito deletério do tampão TRIS nas taxas de crescimento e no conteúdo pigmentar de Gracilaria birdiae Plastino & E.C. Oliveira (Gracilariales, Rhodophyta)). O presente trabalho avaliou os efeitos do tampão Tris (hydroxymethyl)-aminomethane (TRIS) e a interação com a concentração de nutrientes no desenvolvimento em Gracilaria birdiae, espécie presente no litoral brasileiro utilizada comercialmente na produção de ágar. As respostas às diferentes condições de cultivo foram avaliadas por meio das taxas de crescimento e conteúdo pigmentar (clorofila a, ficoeritrina, ficocianina e aloficocianina). A solução de nutrientes de Provasoli com e sem adição de TRIS foi testada nas concentrações de 12,5, 25 e 50%. O pH foi também monitorado. G. birdiae cresceu melhor em ausência de TRIS e em baixas concentrações de nutrientes, 12,5 e 25% (taxas de crescimento de 10,8-11,3%.dia -1 ). As maiores concentrações de ficoeritrina e clorofila a foram observadas na ausência de TRIS em 12,5 e 25% (Ficoeritrina, 649,6-698.0 µg g -1 de biomassa fresca; Clorofila a, 156,0-168,6 µg g -1 de biomassa fresca), evidenciando o efeito deletério do TRIS no crescimento e nos conteúdos de clorofila a e ficoeritrina. Os dados demonstram ainda a importância da utilização de concentrações de nutrientes adequadas em cultivos em laboratório, dependendo das características intrínsecas de cada espécie. Palavras-chave: meio de cultura, TRIS (hydroximetil)-aminometano, Gracilaria birdiae, crescimento, pigmentosABSTRACT -(Deleterious effect of TRIS buffer on growth rates and pigment content of Gracilaria birdiae Plastino & E.C. Oliveira (Gracilariales, Rhodophyta)). This work evaluated the effects of Tris (hydroxymethyl)-aminomethane (TRIS) buffer and its interaction with nutrient concentration on the development of Gracilaria birdie, a common species on the Brazilian coast that has been exploited for agar production. Responses to different conditions were assessed through growth rates and pigment content (chlorophyll a, phycoerythrin, phycocyanin and allophycocyanin). Provasoli's nutrient solution with and without TRIS addition was tested at concentrations of 12.5, 25 and 50%. The pH was also monitored. G. birdiae grew better in the absence of TRIS and at low nutrient concentrations, 12.5 and 25% (growth rates of 10.8-11.3%.day -1). Higher contents of phycoerythrin and chlorophyll a were observed without TRIS at 12.5 and 25% (Phycoerythrin, 649.6-698.0 µg g -1 fresh biomass; Chlorophyll a, 156.0-168.6 µg g -1 fresh biomass). These findings highlight the deleterious effect of TRIS on growth and phycoerythrin and chlorophyll a content. They also demonstrate the importance of appropriate nutrient concentration for laboratory cultures, depending on the intrinsic characteristics of each species.

We studied the chemical structure and yield of low-molecular-mass carbohydrates (LMMC) and soluble polysaccharides produced by green and red morphs of Gracilaria domingensis. Red plants had higher amounts of the LMMC floridoside than green morphs (324.4±8.1 and 220.1±6.0 μmol g-1 dry biomass, respectively). The yield of polysaccharides was similar between morphs (46.3±5.8% for the red and 41.4±8.3% for the green) as was the monosaccharide composition. The same agaran (6-O-methylated and sulphated) was isolated from both morphs, as determined by 13C NMR spectroscopy analysis. The floridean starch content (mg g-1 dry biomass) for the green morphs (116.2±1.7) was lower than that of the red morphs (143.9±1.8). This study showed that green and red morphs of G. domingensis are similar in their polysaccharide composition, but differ in the short-term storage compounds, starch and floridoside. These differences may be related to light and shade photosynthetic strategies, which lead to different storage accumulation.