Salinity is an important abiotic factor since it is responsible for the local and/or regional distribution of algae. In coastal regions, salinity changes with prevailing winds, precipitation and tide, and particularly in extreme intertidal conditions. Acanthophora spicifera is a red seaweed that occurs in the supratidal region in which changes in abiotic conditions occur frequently. Th is study evaluated the eff ects of salinity on the metabolism and morphology of A. spicifera. Algae were acclimatized under culture conditions with sterilized seawater for seven days. Experiments used diff erent salinities (15 to 50 psu) for seven days, followed by metabolic analyses. Th is study demonstrates that extreme salinities aff ect physiological parameters of A. spicifera, such as decrease in growth rate, as well as morphological parameters and concentrations of secondary metabolites. Acanthophora spicifera exhibited high tolerance to 25 to 40 psu, with little change in physiology, which favors the occurrence of this species in diverse environments. However, 15, 20, 45 and 50 psu were the most damaging and led to loss of biomass, depigmentation of apices, and the highest concentrations of antioxidant metabolites. Th e 50 psu treatment caused the greatest changes in general, greatly reducing a biomass and chlorophyll content, and facilitating the presence of endophytes.
By evaluating carotenoid content, photosynthetic pigments and changes in cellular morphology, growth rates, and photosynthetic performance, this study aimed to determine the effect of cadmium (Cd) on the development of young gametophytes of Gelidium floridanum. Plants were exposed to 7.5 and 15 μM of Cd for 7 days. Control plants showed increased formation of new filamentous thallus, increased growth rates, presence of starch grains in the cortical and subcortical cells, protein content distributed regularly throughout the cell periphery, and intense autofluorescence of chloroplasts. On the other hand, plants treated with Cd at concentrations of 7.5 and 15 μM showed few formations of new thallus with totally depigmented regions, resulting in decreased growth rates. Plants exposed to 7.5 μM Cd demonstrated alterations in the cell wall and an increase in starch grains in the cortical and subcortical cells, while plants exposed to 15 μM Cd showed changes in medullary cells with no organized distribution of protein content. The autofluorescence and structure of chloroplasts decreased, forming a thin layer on the periphery of cells. Cadmium also affected plant metabolism, as visualized by a decrease in photosynthetic pigments, in particular, phycoerythrin and phycocyanin contents, and an increase in carotenoids. This result agrees with decreased photosynthetic performance and chronic photoinhibition observed after treatment with Cd, as measured by the decrease in electron transport rate. Based on these results, it was concluded that exposure to Cd affects cell metabolism and results in significant toxicity to young gametophytes of G. floridanum.
This study aimed to examine the evidence of direct interaction among actin, myosin and phosphatidylinositol 3‐kinase (PI3K) in the polarisation and formation of the tetraspore germ tube of Gelidium floridanum.
After release, tetraspores were exposed to cytochalasin B, latrunculin B, LY294002 and BDM for a period of 6 h.
In control samples, formation of the germ tube occurred after the experimental period, with cellulose formation and elongated chloroplasts moving through the tube region in the presence of F‐actin. In the presence of cytochalasin B, an inhibitor of F‐actin, latrunculin B, an inhibitor of G‐actin, and BDM, a myosin inhibitor, tetraspores showed no formation of the germ tube or cellulose. Spherical‐shaped chloroplasts were observed in the central region with a few F‐actin filaments in the periphery of the cytoplasm. Tetraspores treated with LY294002, a PI3K inhibitor, showed no formation of the tube at the highest concentrations. Polarisation of cytoplasmic contents did not occur, only cellulose formation.
It was concluded that F‐actin directs the cell wall components and contributes to the maintenance of chloroplast shape and elongation during germ tube formation. PI3K plays a fundamental role in signalling for the asymmetric polarisation of F‐actin. Thus, F‐actin regulates the polarisation and germination processes of tetraspores of G. floridanum.
Pyropia represents most domesticated seaweed in the world. Therefore, we aimed to determine if cultivation of the red macroalga Pyropia acanthophora E. C. Oliveira and Coll (Rhodophyta: Bangiales) under laboratory conditions would affect the presence and concentration of secondary metabolites. To accomplish this, experiments were performed with ambient sample and acclimated sample (laboratory conditions). The conditions of the culture room were as follows: 24 oC, salinity of 35%o, constant aeration, irradiance of 80 umol.photons.m-2.s-1 and photoperiod of 12 h, for 7 days. Ambient sample showed lower concentrations of allophycocyanin and phycoerythrin when compared to the acclimated sample, but phycocyanin concentration was higher in the ambient sample. Carotenoids showed higher concentrations in the acclimated sample when compared to the ambient sample. Total phenolics were insignificant, while total flavonoids were higher in the ambient sample. No pattern in the production of these secondary metabolites could be identified. On the other hand, the acclimated samples showed a greater inhibition of the free radical DPPH, indicating a higher antioxidant activity. Acclimatization under laboratory conditions, in which P. acanthophora is submerged in seawater, favors the production of economically important secondary metabolites as a result of submersion stress and changes in cultivation patterns, such as irradiance and photoperiod.
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