Kingdom Plantae They include familiar organisms such as trees, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The scientific study of plants, known as botany, has identified about 350,000 extant species of plants, defined as seed plants, bryophytes, ferns and fern allies. In the process known as "photosynthesis ", plants use the energy of the Sun to make food and oxygen. This complex chemical reaction provides nearly all the oxygen in Earth's atmosphere and all the food required by living things. Although some protists and bacteria are capable of performing photosynthesis, plants do most of the photosynthesis on Earth. The ancestors of modern plants evolved in the seas nearly 700 million years ago. These primitive plants did not have many the structures we tend to associate with plants in general, such as roots, stems, and leaves. The evolution of these structures only occurred after plants appeared on land some 265 million years later. Many scientists believe that the evolution of these specialized structures and the wide variety of forms they can assume largely accounts for the success and diversity of land plants we see now.
Phylum Bryophyta • Bryophytes include Liverworts, Hornworts and Mosses. Although most prefer a moist environment, some bryophytes will colonize bare ground. Together with lichens, they are the first plants to appear in a lifeless area. • Though enormously successful in their large number of species distributed throughout the world, Bryophytes are all low-growing plants because they lack the internal food and water-conducting tissues plants need in order to grow to a large size. • There are about 14,000 different species of Mosses, grouped into three main subclasses. Two of these are fairly small, Peat Mosses (Sphagnobrya) and Andreaeobrya. The third is the much larger subclass of the Eubrya which contains most of the world's Mosses. Mosses have stems and leaves but no true roots and no internal plumbing systems.
(Gr. bryon: moss; phyton: plant) A phylum of simple plants possessing no vascular tissue and rudimentary rootlikeorgans (rhizoids). They grow in a variety of damp habitats, from fresh water to rock surfaces. Some use other plants for support. Mosses show a marked alternation of generations between gamete-bearing forms (gametophytes) and spore-bearing forms (sporophytes): they possess erect or prostrate leafy stems (the gametophytegeneration, which is haploid); these give rise to leafless stalks bearing capsules (the sporophyte generation, which is diploid), the latter being dependent on the former for water and nutrients. Spores formed in the capsules are released and grow to produce new plants.
6 classes of Bryophyta: • Takakiopsida - The genus Takakia was established by Hattori and Inoue in 1958 when the gametophyte of T. lepidozioides was found in Japan. In 1963，a species described by Mitten in the hepaticae genus Lepidozia，L. ceratophylla，was transferred to this genus by Grolle. • Sphagnopsida - class of the plant division Bryophyta containing plants commonly called peatmosses. The spongelike plants grow as perennials in soft cushions or lawns in wet habitats (rarely they grow submerged). • Andreaeopsida - A class of the plant division Bryophyta distinguished by longitudinal splitting of the mature capsule into four valves; commonly known as granite mosses.
Andreaeobryopsida - is a genus of moss with a single species Andreaeobryummacrosporum, endemic to Alaska and western Canada. • Polytrichopsida - is a common family of mosses. Members of this family tend to be larger than other mosses with a thickened central stem and a rhizome. The leaves have a midrib that bears lamellae on the upper surface. • Bryopsida - constitute the largest class of mosses, containing 95% of all moss species. It consists of approximately 11,500 species, common throughout the whole world.
Moss growth • Mosses form the largest class of the bryophytes. A magnifying lens can reveal the beauty of some of these tiny plants that have made the transition from water to land. A Moss plant that starts life as a spore grows first into a simple filament or thallus. Then upright leafy branches develop with little rhizoids to anchor the plant and the Moss spreads over the ground, trees or rocks on which it is growing.
Moss sex • Like other Bryophytes, Mosses reproduce sexually, and fertilised eggs develop into sporophytes which can be seen sprouting from the mother plant. Their little stalks are topped by capsules in which the spores develop. Fertilisation takes place only when there is enough water around for the sperm cells to swim to the eggs. Look for the spore capsules of Mosses in the rainy season.
Class Psilopsida • whisk ferns; comprising the family Psilotaceae or Psilotatae: vascular plants with no roots, partial if any leaf differentiation, and rudimentary spore sacs. • A subdivision or class of *vascular plants containing two living genera, Psilotum and Tmesipteris, that together constitute the order Psilotales. • Psilotales - lower vascular plants having dichotomously branched sporophyte divided into aerial shoot and rhizome and lacking true roots.
Whisk ferns (Psilophytes) are an echo of the past and they represent a great step in the evolution of higher plants. 420 million year old fossils show that Psilophytes flourished at that time though very few remain today. One species of the genus Tmesipteris is found in the islands of the Pacific and two species of Psilotum grow in tropical and sub-tropical countries throughout the world. Whisk Ferns
Ancient Psilophytes had branched green stems with no true roots or proper leaves, but they developed an internal system of tubes to carry water and foodstuffs. This made it possible for plants to grow much bigger than the little ground-hugging bryophytes. This picture is a section through the stem of a modern whisk fern showing the internal tubes. Psilotum
Whisk Ferns produce spores which grow into small underground masses of tissue that develop sex organs. The picture shows a section through the spore sacs of a present-day whisk fern. The main plant can be compared to the sporophyte stage of a moss. True ferns which show a similar alternation of sexual and spore-forming generations almost certainly evolved from primitive Whisk Ferns. Whisk Fern Spores