Mosses soak up billions of tons of carbon a year without roots or seeds
Mosses have no flowers, seeds or true roots, and their leaves are often a single cell thick. Yet these small plants absorb an estimated 6.4 billion tons of carbon every year, hold up to 20 times their weight in liquid and form most of the world's peat.
Mosses make up the division Bryophyta, about 12,000 species usually between 0.2 and 10 centimetres tall, though the record-holder, Dawsonia superba, reaches 60 centimetres. They grow in dense cushions and mats, often in shady, damp spots. Thread-like, many-celled rhizoids anchor them instead of roots and can take up water, while most water and nutrients enter through the leaves. Many species are loosely called non-vascular, although some have conducting tissue, just built differently from that of vascular plants and lacking xylem vessels.
Their life cycle turns the usual plant pattern around. In ferns and seed plants the diploid sporophyte is the main, long-lived plant; in mosses the haploid gametophyte, the green leafy plant, dominates. After fertilisation it sends up a short-lived sporophyte, a single unbranched stalk capped by a spore capsule that depends on its parent for water and most nutrients. In most mosses the capsule ripens after the stalk lengthens, the reverse of liverworts.
Details of structure help identification. Stems may stand upright or creep along the ground. Leaves typically lack air spaces and often have a thicker midrib that can run out past the tip, and some end in colourless hair points that look white against the green. Stomata are absent or non-functional in the oldest groups and have been lost more than 60 times in the others. Lichens such as reindeer moss and Iceland moss only look similar; they are symbiotic partnerships, not plants of this kind.
People have used mosses as insulation and absorbent padding, and peat, mostly from Sphagnum, is their main commercial product; gardeners and florists use them too. Ecologically they act as keystone species, helping restore habitats and forests, curbing erosion, filtering polluted air, cooling cities and even suppressing some pathogens dangerous to people.
Source: Moss
