Photoinhibition in the Antarctic moss Grimmia antarctici Card when exposed to cycles of freezing and thawing

Freezing and thawing of the endemic moss species Grimmia antarctici Card, caused photoinhibition. When snow cover was removed from moss in the field, resulting in exposure to fluctuating temperatures and light conditions, photoinhibition, measured as a reduction in the ratio of variable to maximum chlorophyll a fluorescence (F_v/F_m), was observed. The extent of photoinhibition was highly variable and appeared to be reversible during periods of warmer temperatures. A series of controlled laboratory studies found that the light conditions that prevail between freezing and thawing events influenced the recovery from photoinhibition observed during freezing and thawing, with low light conditions facilitating the greatest rates of recovery. After four cycles of freezing and thawing, recovery from photoinhibition in hydrated moss was achieved within 12 h of transfer to 5°C and 15 μmol quanta m^?2 s^?1. These results favour the hypothesis that photoinhibition observed during freezing represents a protective process involving the down-regulation of photo-system II when photosynthetic carbon assimilation is limited by low temperatures.     

Effect of irrigation with saline magnetized water and different soil amendments on growth and flower production of Calendula officinalis L. plants

Global climate change and increased population caused significant depletion of freshwater especially in arid and semi-arid regions including Saudi Arabia. Saline water magnetization before irrigation may help in alleviating the adverse effects of salinity on plants. The current study aimed to examine the potential beneficial effects of water magnetization and soil amendments on growth, productivity, and survival of Calendula officinalis L. plants. Three types of water (tap water “control”, well water, and magnetized well water) and two types of soil amendments (Fe₂SO₄ and peat moss) were examined. Our results showed that irrigating C. officinalis plants with saline well water (WW) adversely affected growth and flowering as compared to tap water (TW). However, plants irrigated with magnetized water (MW) showed significant enhancement in all the studied vegetative and flowering growth parameters as compared to those irrigated with WW. Furthermore, mineral contents and survival of C. officinalis plants irrigated with MW were higher than those irrigated with TW. Irrigation with MW significantly reduced levels of NA⁺ and Cl⁻ ions in leaves of C. officinalis plants indicating the role of magnetization in alleviating harmful effects of salinity. The current study showed that water magnetization enhanced water quality and increased plant’s ability to absorb water and nutrients. Further studies are needed to examine the possibility of irrigating food crops with magnetized water.     

Effect of Calcium and Zinc on Subcellular Distribution, Activity and Thermosensitivity of Superoxide Dismutase in Mnium Affine

In the leafstem moss Mnium affine two superoxide dismutase (SOD) isoforms were found in chloroplasts and two in mitochondria. Four other isozymes were probably cytosolic and two of them had high activity and thermostability and were very sensitive to H₂O₂. On the other hand, one of the mitochondrial isoenzymes was very sensitive to high temperature. The activity and thermosensitivity of SOD was considerably dependent on calcium and zinc ions. The effect was different for the individual isoforms and related to their subcellular distribution. Calcium ions predominantly activated and stabilized one cytosolic and the mitochondrial SODs, while zinc ions influenced one chloroplastic and two cytosolic SODs. This revised version was published online in July 2006 with corrections to the Cover Date.     

Chemical Composition and Cytotoxic Evaluation of the Essential Oil of Phyllogonium viride (Phyllogoniaceae,Bryophyta)

The present study aimed to determine the chemical composition and biological activity of the essential oil obtained from Phyllogonium viride Brid. (Phyllogoniaceae, Bryophyta), whose samples were collected in southern Brazil. For the first time, the cytotoxic activity of the essential oil of P. viride in breast and colorectal tumor cells (MCF-7 and HCT-116) was evaluated, as well as the cytotoxic potential of this oil in non-tumoral cells of human immortalized keratinocytes (HaCaT) via MTT assay. The compounds majorly found in P. viride essential oil were β-bazzanene (20.30 %), β-caryophyllene (17.06 %), β-chamigrene (14.02), and germacrene B (11.72 %). Treatment with P. viride essential oil in the different tested cell lines did not induce any toxicity in most of the tested concentrations. These data contribute to generating new scientific information about this understudied plant species. Furthermore, the chemical characterization of the compounds present in the essential oil of P. viride can lead to greater elucidation of its biotechnological potential.     

The influence of moss on grazers in high‐altitude streams: food,refuge or both?

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Experimental warming alters the community composition,diversity, and N2 fixation activity of peat moss (Sphagnum fallax) microbiomes

Sphagnum‐dominated peatlands comprise a globally important pool of soil carbon (C) and are vulnerable to climate change. While peat mosses of the genus Sphagnum are known to harbor diverse microbial communities that mediate C and nitrogen (N) cycling in peatlands, the effects of climate change on Sphagnum microbiome composition and functioning are largely unknown. We investigated the impacts of experimental whole‐ecosystem warming on the Sphagnum moss microbiome, focusing on N₂ fixing microorganisms (diazotrophs). To characterize the microbiome response to warming, we performed next‐generation sequencing of small subunit (SSU) rRNA and nitrogenase (nifH) gene amplicons and quantified rates of N₂ fixation activity in Sphagnum fallax individuals sampled from experimental enclosures over 2 years in a northern Minnesota, USA bog. The taxonomic diversity of overall microbial communities and diazotroph communities, as well as N₂ fixation rates, decreased with warming (p < 0.05). Following warming, diazotrophs shifted from a mixed community of Nostocales (Cyanobacteria) and Rhizobiales (Alphaproteobacteria) to predominance of Nostocales. Microbiome community composition differed between years, with some diazotroph populations persisting while others declined in relative abundance in warmed plots in the second year. Our results demonstrate that warming substantially alters the community composition, diversity, and N₂ fixation activity of peat moss microbiomes, which may ultimately impact host fitness, ecosystem productivity, and C storage potential in peatlands.