Whittaker's original reclassification was based on the fundamental difference in nutrition between the Fungi and the Plantae. By the middle of the Devonian Period most of the features recognised in plants today are present, including roots, leaves and secondary wood, and by late Devonian times seeds had evolved. Some plants serve as homes for endophytic fungi that protect the plant from herbivores by producing toxins. Encyclopedia of Plant Physiology. From Wikipedia, big city adventure san francisco the free encyclopedia.
For other uses, see Plant disambiguation. Corms are short upright underground stems surrounded by a few thin scale leaves as in Crocus and Gladiolus. Xylem rays, radiating like spokes of a wagon wheel, are formed in the xylem and connect with the peripheral phloem. In addition to vascular tissue, the aerial body is covered with a well-developed waxy layer cuticle that decreases water loss. They are presently distributed in the tropics and subtropics of both hemispheres.
No definition of the kingdom completely excludes all nonplant organisms or even includes all plants. Rhizomes are horizontally growing underground stems that serve as organs of asexual reproduction and food storage. Two types of root systems are commonly distinguished, fibrous roots and taproots. Woody plants are trees and shrubs whose shoots are durable and survive over a period of years. The photosynthetic function is assumed by the stem, and the underground rhizome anchors the plant.
The organisms known as fungi also were once considered to be plants because they reproduce by spores and possess a cell wall. Epiphytes may indirectly harm their host plant by intercepting mineral nutrients and light that the host would otherwise receive.
The way in which the groups of green algae are combined and named varies considerably between authors. The prop roots of corn, for example, are adventitious. An example is the development of a waxy covering the cuticle that covers the plant body, preventing excess water loss.
Palaeobiology of Plant Protists. Sporangia are positioned on the upper adaxial surface of the leaf sporophyll. The Chlorophyta a name that has also been used for all green algae are the sister group to the Charophytes, from which the land plants evolved. Similar to rhizomes, tubers are thickened underground stem portions that primarily serve as food storage for example, potato. They are sterile floral parts and may be either green or leaflike or composed of petal-like tissue.
As noted above, a primary distinction between the gymnosperms and the angiosperms is that the latter have flowers. The cells of the mesophyll contain the photosynthetic pigments. Leaves are supported by the stem and are oriented in a manner conducive to maximizing the amount of leaf area involved in trapping sunlight for use in photosynthesis.
The kingdom Plantae includes organisms that range in size from tiny mosses to giant trees. Evolutionary innovation continued in the Carboniferous and later geological periods and is ongoing today. Stamens are composed of saclike anthers microsporangia and filaments, which are stalks that support the anthers. The xylem moves water and minerals from the root to the rest of the plant, and the phloem provides the roots with sugars and other nutrient produced by the leaves.
Vascular plants differ from other plants in that nutrients are transported between their different parts through specialized structures, called xylem and phloem. See also the list of plant orders.
Despite such differences, plants share the following features common to all living things. Monographs in Systematic Botany. Chlorophyta Streptophyta Chlorokybophyceae Mesostigmatophyceae Spirotaenia. Plantae sensu strictissimo. Primitive flowers are radially symmetrical actinomorphic and are characterized by numerous spirally arranged floral parts.
The root system is involved in the uptake from the soil of water and minerals that are used by the root system as well as the stem and leaves. Space Time Energy Matter Change.
In contrast, most other algae e. In addition, the water-conducting cells and food-conducting tissue are more complex and efficient in flowering plants than in other land plants.
The spore case is flattened, with a layer of sterile, or nonfertile, cells surrounding the spore mother cells. The cone-bearing gymnosperms are among the largest and oldest living organisms in the world. Thread used to sew cloth likewise comes in large part from cotton.
Most of the solid material in a plant is taken from the atmosphere. Leaves are classified on the basis of leaf arrangement and whether they are simple or compound. The Coal measures are a major source of Paleozoic plant fossils, with many groups of plants in existence at this time.
Paleobotany and Evolutionary history of plants. Plant proteins, mostly globulins, have been obtained chiefly from the protein-rich seeds of cereals and legumes. Simple plants like algae may have short life spans as individuals, but their populations are commonly seasonal. Petals collectively called the corolla are also sterile floral parts that usually function as visually conspicuous elements serving to attract specific pollinators to the flower.
Female trees produce plumlike seeds with a fleshy outer layer and are noted for their foul smell when mature. The Classification of Lower Organisms. The weight of large numbers of epiphytes may break tree limbs. Glaucophyta Rhodophyta Picozoa. In the mosses and hornworts a cuticle is usually only produced on the sporophyte.
Most species of bryophytes remain small throughout their life-cycle. Cell division is also characterized by the development of a phragmoplast for the construction of a cell plate in the late stages of cytokinesis. Other species have gametophytes bearing both sex organs. The Biology and Evolution of Fossil Plants.
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