Basking in the sun: how mosses photosynthesise and survive in Antarctica.

The Antarctic environment is extremely cold, windy and dry. Ozone depletion has resulted in increasing ultraviolet-B radiation, and increasing greenhouse gases and decreasing stratospheric ozone have altered Antarctica's climate. How do mosses thrive photosynthetically in this harsh environment? Antarctic mosses take advantage of microclimates where the combination of protection from wind, sufficient melt water, nutrients from seabirds and optimal sunlight provides both photosynthetic energy and sufficient warmth for efficient metabolism. The amount of sunlight presents a challenge: more light creates warmer canopies which are optimal for photosynthetic enzymes but can contain excess light energy that could damage the photochemical apparatus. Antarctic mosses thus exhibit strong photoprotective potential in the form of xanthophyll cycle pigments. Conversion to zeaxanthin is high when conditions are most extreme, especially when water content is low. Antarctic mosses also produce UV screening compounds which are maintained in cell walls in some species and appear to protect from DNA damage under elevated UV-B radiation. These plants thus survive in one of the harshest places on Earth by taking advantage of the best real estate to optimise their metabolism. But survival is precarious and it remains to be seen if these strategies will still work as the Antarctic climate changes.

Comparison of solvent regimes for the extraction of photosynthetic pigments from leaves of higher plants.

The relative efficiency of methanol- and acetone-based solvents for the extraction of pigments from photosynthetic tissues of plant was compared, together with the advantages of multiple versus single extractions. The two commonly employed triple acetone extractions (100 : 80 : 80% and 85 : 100 : 100%) performed comparably for most pigments and for all plant species tested. Single extractions with either 96% methanol or 85% acetone failed to extract the more hydrophobic pigments, especially ß-carotene. We conclude that multiple extractions that combine pure and aqueous (80-85%) acetone are preferable for extraction of the full range of pigments. These results suggest that previous studies that have utilised aqueous methanol (especially in a single extraction) have probably underestimated the concentration of ß-carotene relative to other pigments.