Use and Technology
Bioremediation has been used on a large scale mostly to treat oil spills. The best example of this was during the Exxon Valdez oil spill in Alaska in 1989. Rather than try to remove oil from beaches physically by steam spraying or absorbing it into other materials , engineers sprayed several beaches with a nutrient solution that helped naturally occurring oil-degrading microbes in the environment to multiply and begin decomposing the pollutant. The experiment was successful, and the U.S....
Pteridophytes
The pteridophytes were much more advanced than the bryophytes. While the structure of the bryophytes was primarily cellular, that of the fern plant is vascular. Unlike the bryophytes, the pteri-dophytes originate from a fertilized egg and produce spores. Pteridophytes are well represented by the ferns, which have existed from the Devonian period. Another class of pteridophytes is the horsetails Equisetales , which also have existed from the Devonian to the present. The third class of...
Superior or Inferior Ovaries
The position of the ovary also varies among different flower types. A flower has a superior ovary when the base of the ovary is located above where the sepals, petals, and stamens are attached. This point of attachment is referred to as the receptacle or hypanthium, the fused bases of the three floral parts tulips and St. John's wort are examples . An inferior flower has an ovary below where the sepals, petals, and stamens are attached as do daffodils and sabatia . Some flowers show an...
Benefits of Fire
Some plant species require very high temperatures for their seed casings to split for germination. After fire periodically sweeps through the forest, seeds will germinate. Other species, such as the fire-resistant ponderosa pine, require a shallow layer of decaying vegetable matter in which to root. Fires burn excess debris and small trees of competing species and leave an open environment suitable for germination. Dead material on the forest floor is processed into nutrients more quickly by...
Economic Uses
Outside the grasses, such as wheat, corn, and rice all in the monocot family Poaceae , most plants of economic importance are eudicots. Examples of economically important eudicot families include members of the bean or legume family Fabaceae , such as soybean, lentils, and green beans and the sunflower family Asteracae , which includes sunflowers, lettuce, and artichokes. The mustard family Brassicaceae contains numerous members of economic importance, including cabbage, kale, cauliflower,...
The Paleozoic Era
The Proterozoic and Archean eons have restricted fossil records and predate the appearance of land plants. Seedless, vascular land plants appeared in the middle of the Silurian period 437-407 mya and are represented by the rhyniophytes or rhyniophytoids and possibly the Lycophyta lyco-phytes or club mosses . From the primitive rhyniophytes and lycophytes, land vegetation rapidly diversified during the Devonian period 407360 mya . Pre-fern ancestors and maybe true ferns Pterophyta were developed...
Evolutionary Advantages and Uses
The recognition of extranuclear genetic systems raises important questions about their possible evolutionary advantage. In contrast to the remarkable universality of the nuclear genetic system, extranuclear genetic systems are quite diverse in function and mechanisms of transmission. Although extranuclear genes control only a small fraction of the total hereditary material of the cell, in eukaryotic organisms the genes found in mitochondria and chloroplasts are clearly essential for maintaining...
Equity and Environmental Issues
The Green Revolution has promoted input-intensive agriculture, which has, in turn, created several problems. In theory, a small-scale farmer will get benefits from planting the HYV seeds that are similar to those reaped by a large farm. In practice, however, small-scale farmers have had more difficulty in gaining access to Green Revolution technology. To use the new seeds, fields need adequate irrigation and the timely application of chemical fertilizers and pesticides. In many developing...
Water Erosion
There are several types of wind and water erosion. The common steps in water erosion are detachment, transport, and deposition. Detachment releases soil particles from soil aggregates, transport carries the soil particles away and, in the process, scours new soil particles from aggregates. Finally, the soil particles are deposited when water flow slows. In splash erosion, raindrops impacting the soil can detach soil particles and hurl them considerable distances. In sheet erosion, a thin layer...
Reproduction 1
Pterophytes such as ferns exist as two alternating forms during their sexual reproductive cycle. Initially, in the gametophyte phase, ferns are a stem known as the rhizome, from which roots and leaves, called fronds, grow as the fern matures into an adult sporophyte. The sporophyte exists separately from the gametophyte, which usually dies as soon as the sporophyte's root sinks into soil. Growing on or near the soil surface, rhizomes, the most common stem form, can be as thin as threads or as...
Medicinal Plants
Categories Economic botany and plant uses medicine and health Because plants are so biochemically diverse, they produce thousands of substances commonly referred to as secondary metabolites. Many of these secondary metabolites have medicinal properties that have proven to be beneficial to humankind. The use of plants for medicinal purposes predates recorded history. Primitive people's use of trial and error in their constant search for edible plants led them to discover plants containing...
Hardyweinberg Theorem
The Hardy-Weinberg theorem is the principal that, in the absence of external pressures for change, the genetic makeup of an ideal population of randomly mating, sexually reproducing diploid organisms will remain the same, at what is called Hardy-Weinberg equilibrium. Population genetics is the branch of genetics that studies the behavior of genes in populations. The two main subfields of population genetics are theoretical or mathematical population genetics, which uses formal analysis of the...
Genetic Drift
Categories Ecology genetics reproduction and life cycles Genetic drift refers to random changes in the genetic composition of a population. It is one of the evolutionary forces that cause biological evolution, the others being selection, mutation, and migration, or gene flow. Drift occurs because the genetic variants, or al-leles, present in a population are a random sample of the alleles that adults in the previous generation would have been predicted to pass on, where predictions are based on...
Flower Types
The flower is the most distinctive feature of the phylum Anthophyta, commonly referred to as angiosperms or flowering plants, and is responsible in making them the most dominant, diverse, and widespread of all groups of plants. There are already about 250,000 species of flowering plants that have been discovered and named. The basis for their diversity comes from their incredible reproductive success in a wide variety of habitats. The success of this group is also reflected by the diversity of...
Gametophytes and Sporophytes
All vascular plants, as well as mosses and liverworts and many algae, display a type of life cycle referred to as alternation of generations, which involves two distinct life-forms, the gametophyte and sporophyte. The sporophyte generation is genetically diploid and, as the name implies, produces spores by meiosis. Spores germinate and develop into gametophytes, which are genetically haploid and produce gametes eggs and sperm by mitosis. Sporophytes are larger than gametophytes and represent...
Gymnosperms
Categories Gymnosperms Plantae taxonomic groups Pine trees are a familiar example of gymnosperms, a series of evolutionary lines of woody vascular seed plants that produce seeds not encased in an ovary. Two kinds of higher plants the gymnosperms and angiosperms have developed to become the dominant type of land plant. With the exception of a few aquatic angiosperms, they do not require water for pollen transfer and are thus free to live in a wide variety of habitats. Gymnosperms and angiosperms...
Cell Covering
Members of the Pavolophycidae lack body scales. However, cells of species placed in the Prymnesio-phycidae are covered by organic base plate scales, mineralized calcium carbonate scales, or a combina tion of both that are external to the plasmalemma. Nearly 70 percent of all known species of prym-nesiophytes are known as coccolithophorids. The external covering of these cells is composed of mineralized calcium carbonate calcite scales termed coccoliths. Individual coccoliths are intricately...
Complete and Incomplete Flowers
A flower that has all four whorls of floral parts is said to be a complete flower such as the hibiscus and the lily . An incomplete flower lacks any one or more of these parts such as those of elms, willows, oaks, and plantains . With or without sepals and petals, a flower that has both stamen and pistil is called a perfect flower. Thus, all compete flowers are prefect, but not all perfect flowers are complete. In contrast, flowers that have only stamens or only pistils are called imperfect...
Divergent Evolution
Some of the most famous examples of divergent evolution have occurred in the Gal pagos Islands. The Gal pagos comprise fourteen volcanic islands located about 600 miles west of South America. A total of 543 species of vascular plants are found on the islands, 231 of which are endemic, found nowhere else on earth. Seeds of various species arrived on the islands by floating in the air or on the water or being carried by birds or humans. With few competitors and many different open habitats,...
Meristems
Apical meristems are located at the growing tips of the plant there are apical meristems in the roots and in the buds on shoots of the aboveground part of the plant. New cells produced at the meristems are initially undifferentiated. They enlarge in the adjacent zone of elongation, mostly by increasing their water content. These cells eventually differentiate into the plant's primary tissue types dermal, vascular tissue, and ground tissues. Other meristematic tissue occurs along the stem, and...
Mitigation Attempts
International conferences have been held, and international organizations have been established to research and minimize potential detriments of global warming. In 1988 the United Nations Environment Programme and the World Meteorological Organization established the International Panel on Climate Change IPCC . The IPCC has conducted much research on climate change and is now considered an official advisory body on the climate change issue. In June, 1992, the United Nations Conference on...
Types of Inflorescence
Flowers may be solitary, or they may be grouped together in an inflorescence, a cluster of flowers. An inflorescence has one main stalk, or peduncle.Itmay also bear numerous smaller stalks called pedicels, each with a flower at its tip. The arrangement of pedicels on a peduncle characterizes different kinds of inflorescences. Some of the common types of inflorescences are as follows Spike The flowers, which are with a very short or with no pedicel, are attached along the elongate and unbranched...
Primary and Secondary Tissue
In many species, the new cells in the sporophyte are produced primarily by the division of apical meristems, thus consisting almost exclusively of primary tissues. There are, however, some plants in which the sporophytes grow in girth. Some of these such as the calamites giant horsetails , the Lepidodendron tree lycopods , and the seed ferns are known only from the fossil record. Others are the trees and shrubs, so-called woody plants, that characterize the modern forests. The wood of woody...
Growth Control
The patterns of secondary organ formation are controlled both by genetic factors and by environmental conditions. Horticulturists use plants as a source of dwarfing stocks that have a genetic predisposition to form branches early. In many cases, the dwarfing results from a failure of the stem to elongate in the internodes the regions between the nodes, where leaves and lateral branches originate . Dwarfing appears to be particularly influenced by plant hormones called gibberellins, which...
Liquid Transport Systems
Categories Anatomy physiology transport mechanisms Liquid transport systems are structures that facilitate the movement of water, via the xylem,from a plant's roots to its leaves. Water then evaporates from the leaves through the stomata in the process of transpiration. Water is the most abundant compound in plant cells. It accounts for 85-95 percent of the weight of most plants. It even makes up 5-10 percent of the weight of dry seeds. More than 95 percent of the water gathered by a plant,...
Habitats 1
Marine plants live in diverse habitats near shores or in salt marshes and open seas worldwide. Giant kelp, a seaweed found in the South Pacific, grows in groups in warm coastal waters. In contrast, sea ice algae live on floating ice sheets. Migrating marine plants drift in a variety of water conditions. On reefs, marine plants have several roles. Primarily, marine plants, including macroalgae and sea grasses, provide nourishment and shelter for animals. Marine plants assist corals in...
Fluid Mosaic Model
In the 1960's it was believed that all cellular membranes were structured as two outer layers of protein surrounding a lipid layer. In 1972 Jonathan Singer and Garth Nicolson proposed the now-accepted fluid mosaic model. The lipid component of the membrane forms the basic structure, while the proteins act as enzymes, receptors, and transporters. The lipid molecules, most of which are phospholipids, each have a hydrophilic water-loving end and a hydrophobic water-fearing end and associate...
Amino Acids to Proteinoids
In order to form proteins, amino acid molecules must lose some water from their molecular structures, which happens when amino acids are heated to temperatures of 140 degrees Celsius. Volcanic activity would have been capable of providing such temperatures. A biochemist named S. W. Fox and his coworkers were able to produce proteinlike chains from a mixture of eighteen common amino acids. Fox termed these structures proteinoids and thought that billions of years ago proteinoids were the...
Ferns
Categories Paleobotany Plantae seedless vascular plants taxonomic groups Ferns are among the most recognizable members of the phylum Pterophyta, which are primitive, nonflowering, vascular plants that primarily reproduce by spores and occur in many variations, complicating classification. Approximately twelve thousand extant species of fern are classified in the phylum Pterophyta. These seedless plants display a diversity of physical and reproductive characteristics that separate them...
Other Endomembrane System Components
From the above, it can be seen how the ER and Golgi complex interact to deliver proteins and carbohydrates to the plasma membrane and vacuoles. In addition, the electron microscope often shows the ER to be physically connected to the nuclear envelope. Thus, the nuclear envelope is almost always included in a discussion of the endomembrane system. However, the exact functional nature of this nuclear connection remains unknown. The nuclear envelope is composed of two membranes, the outermost of...
Endomembrane System
The internal membranes of eukaryotic cells are dynamic, constantly changing structures. The concept of the endomembrane system describes all internal cytoplasmic membranes, with the exception of mito-chondrial and plant plastid membranes, as a single continuum. In this model, the ER, generally the largest membrane system of eukaryotic cells, is the initial source of most other membranes. The ER is a network of interconnected, closed, membrane-bound vesicles that is contiguous with the nuclear...
Medicinal Uses
Aerial stems develop from horizontal rhizomes, which are highly branched and perennial. Because the rhizomes can grow quite rapidly, Equisetum is often invasive. If livestock pastures are invaded by Equisetum, it can cause problems for farmers and ranchers, as the aerial stems of Equisetum are poisonous. Equisetum arvense, a species found in the United States and southern Canada, is especially toxic in dry hay. Horses, sheep, and cows are all susceptible to Equisetum poisoning. Symptoms include...
Cycadeoids Cycads and Conifers
When the coal swamps dried up, the pterido-sperms and the cordaites were replaced by the cy-cads, cycadeoids, and conifers. The cycads and cy-cadeoids evolved from the medullosan seed ferns. The cycads and cycadeoids were among the dominant plants during the age of the dinosaurs. The conifers are related to the cordaites. Some cycadeoids had slender, branching trunks, while others were short and stumpy. Both types had compound leaves. Cycadeoid cones contained both male and female reproductive...
Evolution Of Plants
Categories Evolution paleobotany Plantae As a result of prehistoric events such as the Permian-Triassic extinction event and the Cretaceous-Tertiary mass extinction event, many plant families and some ancestors of extant plant were extinct before the beginning of recorded history. The general trend of earth's plant diversification involves four major plant groups that rose to dominance from about the Middle Silurian period to present time. The first major group providing land vegetation...
Isoflavonoids as Phytoestrogens
Isoflavonoids are a type of secondary metabolite and are found almost exclusively in the legume pea family of plants. They are known to function in plant defense. They have been shown to deter herbivores and also to facilitate a plant's defense response to pathogen attack. Interestingly, some isoflavonoids have chemical structures that, in overall size, shape, and polarity, resemble estrogens. The resemblance includes the flatness, or planarity, of the molecules and the positions and...
Leaf Margins 1
The margin is the edge of the leaf lamina lying between the apex and base. Entire margins are smooth, without indentations or incisions. Revolute margins are rolled downward, toward the lower surface of the leaf. Involute margins are rolled upward, or toward the upper surface of the leaf. Repand margins are slightly and irregularly wavy, with the lamina surface undulating in a downward and upward direction. Sinuate leaf margins are shallowly indented and strongly wavy in the horizontal plane.
Lobing
Lobes typically extend greater than one-eighth of the distance from the margin to the midrib of the leaf or leaflet. The margin is the edge of the leaf lamina lying between the apex and base. The midrib is the prominent vein that subdivides the leaf or leaflet into two halves from base to apex. Pal-mately lobed margins are indented toward the base of the leaf lamina, creating a pattern like fingers extending from a hand, or a digitate pattern. Pinnately lobed margins are indented one-quarter to...
Common Herbs
Among the herbs most commonly used in cooking are members of the Lamiaceae, or mint, family. Mint, rosemary, basil, oregano Origanum vulgare , sage Salvia officinalis , thyme Thymus vulgaris , and marjoram Origanum majorana are the most frequently used members of this family. These herbs are important staples in most cuisines of the Mediterranean region. The key features that most mint family members share are square stems and simple leaves having undivided blades attached in groups of two...
Haptophytes
Categories Algae Protista taxonomic groups water-related life The algal phylum Prymnesiophyta, or Haptophyta, is a dred extant species that are 4-40 microns in size. The phylum Haptophyta is divided into two subclasses, the Prymnesiophycidae and Pavlovophy-cidae, that differ significantly from one another see below . The phylum is usually classified within the kingdom Chromista with other algae containing chlorophyll a and c excluding dinoflagellates , but their exact relationship to the...
Sources for Further Study Tub
Asthana, A. K., and S. C. Srivastava. Indian Hornworts A Taxonomic Study. Berlin J. Cramer, 1991. An edition of the series Bryophytorum Bibliotheca, which describes and classifies hornworts indigenous to the Indian subcontinent. Includes illustrations, map, and bibliography. Crum, Howard A. Liverworts and Hornworts of Southern Michigan. Ann Arbor University of Michigan Herbarium, 1991. A study focusing on the identification and classification of bryophytes growing in Michigan. Includes...
Angiospermlike Features
The gnetophytes share with the angiosperms a number of structural and developmental characteristics. One of these is the presence of water-conducting tubes, called vessels, in the secondary xylem, or wood. Vessels, although present in angio-sperms, do not occur in gymnosperms other than gnetophytes. Another similarity is that archegonia structures that protect the egg which are typical of gymnosperms but absent from angiosperms, are not found in either Gnetum or Welwitschia although they are...
Heterokonts
Categories Algae economic botany and plant uses microorganisms pests and pest control Protista water-related life Heterokonts are a group of closely related phyla withflagella in pairs, one long and one short. They include oomycetes, chrysophytes, diatoms, and brown algae. The term heterokont refers either to the flagellar arrangement of biflagellate cells in which the two flagella differ in length as in anisokonts , type of motion, or ornamentation, or to those organisms and organisms...
Fruit Types
Fruits can be classified, based on the nature of the pericarp, into two groups fleshy and dry. Fleshy fruits, in turn, are classified into several types, including drupes, berries, pomes, hesperidia, and pepos. Dry fruits are also subdivided into several categories, including follicles, legumes, capsules, achenes, nuts, samaras, schizocarps, and caryopses. The three most familiar types of fleshy fruits are drupes, berries, and pomes. Adrupe is a fleshy fruit that contains a single seed...
Thallophytes
The earliest fossil plants are represented by a phylum called the thallophytes. The geological record of the thallophytes is incomplete. Of seven large groups, only a few are represented by fossils. Although some records from the Paleozoic era have been found, the earliest identifiable specimens found are from the Jurassic period. The dearth of fossils from this group of plants can be attributed to their minute size and the fragile nature of their remains. The thallophytes are in the most...
Indeterminate Inflorescences
A catkin also known as an ament is a spikelike inflorescence. Dissection may reveal the presence of minute, and possibly branched, pedicels. The flowers are typically unisexual and are hidden by bracts. This inflorescence is typical of trees such as oaks, hickories, and birches. A corymb is a flat- or rounded-top inflorescence. The pedicels of flowers are attached along the length of the peduncle. Corymbs may be simple or compound. Examples include hydrangea and hawthorn. A head, or capitulum,...
Sources for Further Study Vdz
Conrad, Henry Shoemaker, et al. How to Know the Mosses and Liverworts. 2d ed. New York McGraw-Hill, 1979. Guide to identification achieves middle level of coverage neither too simple nor too technical . Includes line drawings. Greenaway, Theresa. Mosses and Liverworts. New York Raintree Steck-Vaughn, 1992. Focuses on varieties and life cycles of mosses and liverworts in different climates and habitats. Includes index. Watson, E. Vernon. British Mosses and Liverworts. 3d ed. New York Cambridge...
Germination And Seedling Development
Categories Anatomy physiology reproduction and life cycles With germination, the growth of a seedling, spore, or bud begins. Seedling development begins with the close ofgermina-tion. To germinate, seeds must be nondormant and in a suitable environment. Seeds germinate within a restricted range of temperatures, moisture, oxygen, light, and freedom from chemical inhibitors. Wild seeds display many adaptations that predispose germination within specific habitats and seasons. By contrast, seeds of...
Functions of Flower Parts
Flowers and their parts function to achieve sexual reproduction, including pollination and seed formation. After pollination is finished, the flower begins the process of seed and finally fruit formation. During pollination, pollen grains are released from the anther and carried to the stigma, either by animals such as insects, birds, and bats or by wind. Animals, attracted by the flower's colors or aromas, visit flowers to obtain food either the pollen itself or the nectar, a sugary liquid...
Breaking Chemical Bonds
The energy in glucose is locked up in the chemical bonds that hold the molecule together. The process of glycolysis breaks these chemical bonds in a series of carefully controlled chemical reactions. Each reaction can be greatly accelerated by the appropriate enzyme. Generally, cells have sufficient quantities of the necessary enzymes present at all times. Each chemical step is regulated by either the amount of raw materials present or the amount of finished product. If the raw materials are in...
Blooming Habits Roses and Lilies
Wild rose plants have regular, single flowers, with five petals. In most cultivars double flowers, having petals numbered in multiples of five, are produced. The flower also has a calyx with five lobes, many stamens, and one or more carpels. Rose sprouts have two seed leaves, so the plants are eudicots. Flowers of most cultivars bear few seeds, and the majority of them are sterile. The number of seeds is small because in double roses, flower parts that would otherwise produce seeds become extra...