61 Ferns, Mosses & Conifers

Tropical Topics An interpretive newsletter for the tourism industry Plants without flowers — lichens, mosses, ferns and conifers No. 61 April/May 2000 Mini-ecosystem on a leaf Notes from the In the forest we tend to concentrate on the big picture — the whole forest, the magnificent trees and any animals we can spot in and around them. We focus on Editor the fresh green (or new red) leaves and tend to ignore those which look a bit Following on from the December blotchy, dirty and old. However, a closer look may reveal an entire ecosystem, issue of Tropical Topics (No. 59) with whole communities of tiny plants and animals flourishing right there on which focussed on cycads, this the surface of the leaf. issue looks at the other main groups of plants which manage The little plants which live on leaves many rainforest leaves are shiny and without flowers. They have ancient are called epiphylls. ‘Epi’ means their shape, designed to encourage origins and flourished back in ‘upon’ and ‘phyll’ means ‘leaf’. water to run off quickly, is thought to Mesozoic times when dinosaurs (Epiphyte, the more familiar name used reduce the ability of epiphylls to roamed the earth and flowering for a number of ferns, orchids and so colonise them. plants had not yet made an on, means ‘upon-plants’.) Epiphylls appearance. include a variety of non-flowering Nonetheless, epiphylls are an plants including lichens (the main important part of the whole Botanists who study these plants group), mosses, leafy liverworts and rainforest ecosystem. They are can only dream of the time when algae. Twenty species, or more, may also a sensitive bunch and can ferns formed forests and conifers be found on a single leaf. They be disturbed by human proliferated in the southern flourish best where light levels are low, activities. Loss of hemisphere as well as to the north. on leaves in the understorey. Indeed, habitat has left They consider these plants to be almost every understorey leaf them vulnerable now in their ‘sunset years’, in the supports at least a few of these plants and recent process of being superseded by the research dominant angiosperms. and among them lives an entire Nonetheless, the plants we see microscopic fauna population of mites, suggests that today are the survivors. Some, such worms and insect larvae as well as some may as the seed ferns, giant clubmosses bacteria and a number of fungi function as and giant horsetails became extinct. species. We often talk of biodiversity good However, despite competition from in rainforests in terms of the indicators flowering plants which were able to bewildering number of tree species but of forest reproduce more efficiently and the variety of microscopic epiphylls stress. adapt to different conditions more and their dependent animals make a quickly, an impressive and very valuable contribution to this. fascinating variety of non-flowering plants have held their ground. Many of the bacteria which live on leaves play an important part in the Tour-op tip rainforest ecosystem by using Take a magnifying glass or hand nitrogen from the atmosphere and lens with you into the rainforest to recycling nutrients. However, show visitors the leaf-top epiphylls can be quite a burden for a ecosystems. However, please bear plant. A heavy population of them on in mind that epiphylls are sensitive. a leaf significantly reduces its ability Handle the leaf with care (do not to photosynthesise (produce food break, tear, squash or remove it) from sunlight). To discourage this and avoid touching the epiphylls. I would like to thank Gary Wilson of the Queensland Herbarium for An excellent small brochure with coloured, magnified photos, has been his very valuable assistance with produced by the Rainforest CRC. Miniature Gardens on Rainforest Leaves: A this issue. guide to common epiphylls in the Wet Tropics can be obtained by contacting them on Ph: 4042 1246 or via PO Box 6811, Cairns, QLD 4870. Small and flowerless Algae Lichens could perhaps be regarded as terrestrial algae. were the They are remarkable organisms. Each is a combination of an first alga (blue-green or green) and a fungus, functioning proper together in a symbiotic partnership. The fungus provides the plants to ‘root system’ (hyphae), drawing up water and minerals for the evolve and pair. The rootless alga has the chlorophyll, the green stuff in Foliose lichen green algae most plants which enables them to photosynthesise — to create food from are the ancestors of all of today’s land sunlight. To do so the alga needs the water provided by the fungus, while the plants. They are very simple cellular fungus needs the food manufactured by the alga. Together they are a lichen. plants, with no roots, stems or flowers. Generally the fungal threads create the body of the lichen with the algal cells While most are found in water bodies, living within them. This gives the lichen strength and prevents the alga from salt and fresh, the notorious blue- drying out. The fungi also manufacture a type of acid which serves to eat away at green algae forming blooms where underlying rock and provide the lichen with a foothold. Lichens therefore erode nutrient loads are high, others are rock, very slowly. It has been estimated that they produce a centimetre of topsoil found on land where conditions are in two thousand years. moist. Small forms grow as parasites below the ‘skin’ (the cuticle) of Many lichens produce small powdery granules called soredia on their surface. rainforest leaves. These contain both algal cells and fungal threads. When washed or blown away, or carried by insects, they grow into new lichens. Larger upright packets (isidia) Mosses represent an evolutionary work in a similar way. However, sometimes the fungal partners make their own step up from algae. They have no fruiting bodies. These vary in appearance, resembling small volcanoes, cups or roots and no system of woody vessels jam tarts. When these burst, the fungal spores are dispersed but if they do not which allow more advanced plants to pair up with the correct algal cells they cannot develop. (The algal cells, on the grow tall. As the first land plants other hand, are able to live independently.) mosses probably created the first forests, mini-ecosystems just 5cm or Lichens grow on rocks, walls, trees, fences, roofs and on the ground, as well as so high, achieving this impressive on leaves. They are limited by light, needed by the algae for photosynthesis, and height simply by packing themselves also need clean air. The presence of sulphur dioxide, produced when fuels such tightly together. as coal and oil are burned, and which is responsible for acid rain damage, kills Spore capsules lichens. These plants are therefore good indicators of a clean There are three main types environment. Since some are more . tolerant of pollution than others, the of lichens type of lichen growing can tell us how Crustose bad the pollution is. However, lichens lichens form are very hardy in natural conditions, flat crusty living in the tropics, on mountain tops, plates. They in salty seashore splash zones and grow very The sex even polar regions, where they survive slowly outwards life of temperatures well below freezing. They around the margin, mosses can stop growing if conditions are dry, increasing their radius by resembles the resuming when moisture returns and as little as 0.5mm a year. complicated system of are usually the first organisms to alternate generations found in algae. invade barren ground, such as new However, mosses keep the next lava flows. Here they provide a generation at home! Whereas algal foothold for other plants to move in. male and female cells meet by swimming freely through the water, female moss cells are attached firmly to The human element the parent plant. When they have Lichens were used traditionally in been fertilised by free-swimming male many countries to make dyes for cloth, Foliose cells they grow into spore-filled notably Harris tweed, in Scotland. The lichens capsules on the end of long stalks. dye litmus is also derived from lichens. are leafy in appearance, although These capsules eventually open to It changes to red when exposed to an the lobed or branched structures are release the spores which are blown acid and blue when exposed to an not true leaves. They often grow away to grow into new moss plants. In alkali. An infusion of the lichen near mosses. some respects, this tendency to retain lungwort was used for treating coughs the female egg on the parent plant and asthma. resembles the habit of later plants, such as cycads, conifers and flowering Reindeer ‘moss’, the staple diet of plants, to do the same. Perhaps it reindeer and caribou in winter, when represents a step along the nothing else grows, is actually a Fruticose evolutionary way. lichen. Unfortunately, because lichens lichens tend to accumulate certain are even Liverworts are very similar to environmental contaminants, after the more finely branched and may hang mosses. However, where the pointed Chernobyl nuclear power plant down like beards from branches or ‘leaves’ of mosses are arranged in accident in 1986 reindeer ‘moss’ grow up from the ground like tiny spirals on the stems, liverworts have accumulated so much radioactivity shrubs. These last two are rounded (liver-shaped) ‘leaves’ which that the Saami people who live in the particularly fussy about clean air grow flat in double rows. Arctic were unable to eat their but grow faster than the crustose reindeer. lichens. 2 Out and about At this time of year the weather About a year ago, in Out and About patterns are changing, our rain coming (Tropical Topics No.

Load more