Module 1 - General Botany - PDF

Don Mariano Marcos Memorial State University South La Union Campus COLLEGE OF ARTS AND SCIENCES Agoo, La Union MODULE I INTRODUCTION Lesson 1 Introduction to Plants and Botany Lesson 2...

Don Mariano Marcos Memorial State University South La Union Campus COLLEGE OF ARTS AND SCIENCES Agoo, La Union MODULE I INTRODUCTION Lesson 1 Introduction to Plants and Botany Lesson 2 Origin and Evolution of Plants Lesson 3 Diversity and Plant Adaptations Lesson 4 Overview of the Domains of Life Module I  2 MODULE I INTRODUCTION This module presents the study of plants. It is hoped that you will learn to appreciate plants since you are in close contact with them every day. After studying the module, you should be able to: 1. Discuss the importance of plants, differentiate pure and applied botany, and understand plants using concepts. 2. Understand the origin and evolution of plants. 3. Express appreciation on how plants deal with the requisites of survival. 4. Understand the place of plants with other organisms. There are four lessons in the module. Read each lesson carefully, then answer the exercises/activities to find out how much you have benefited from it. Work on these exercises carefully and submit your output to your tutor or to the BPSD office. In case you encounter difficulty, discuss this with your tutor during the face-to-face meeting or contact your tutor (Dr. Ofelia E. Aspiras @ 09178770811 and [email protected] at the College of Arts and Sciences. Good luck and happy reading!!! Module I  3 Lesson 1 So, let us start with the discussion of the first lesson, introduction to plants and botany. When we say Botany, this is the scientific study of plants. It deals with the structure, physiology, reproduction, evolution, diseases, economic uses, and other features of plants. The word botany can be traced to the ancient Greek word “botane” which means plant. This word, in turn, can be traced back to the Greek word “boskein,” to graze, which is derived from “buos,” the Greek word for cattle. Hence, etymologically, botany is the science of what cattle eat. Plants, on the other hand, are organisms that produce spores (like that found in the picture of fern frond below) and which have cellulose (a component of the cell wall), a complex carbohydrate that serves as their coverings. The essential feature of green plants is their ability to synthesize or make their own metabolic compounds from simple substances such as salts, carbon dioxide, and water in a process known as photosynthesis (to be discussed in detail later). Over 550,000 species of plants clothe the earth and inhabit most of the waters to a depth of approximately 100 feet. Figure 1. Spores (under a microscope and those are found inside the sporangium) Module I  4 Now, let us talk about the history of botany. Man has been concerned with plants throughout his history. For thousands of years, he used them for one purpose or another, but there was no science of plants until the days of the Greeks. The botany of today is the result of many years of progress and development. In early civilization, the curative virtues of plants made people interested, and the careful study of these was prepared by medical men. In 1500 B.C., there has been a list of Egyptian drug plants with their uses. The list includes Acanthus, Aloes, beans, Crocus, dates, linseed, onion, poppy, and many others. As a cure for scurvy, for example, it was recommended to use a mixture of cypress, onion meal, incense, and the juice of wild dates. The effectiveness of the mix can also be found as a proven remedy in the temple of Osiris. The nature of plants was studied by Aristotle (384-322 B.C.) As a teacher and friend of Alexander the Great, he was able to get specimens and described plants and animals from most of the world then known, and he was the first man to become familiar with a wide range of biological facts. He has a disciple, Theophrastus of Eresus (371-287 B.C.), whom present-day botanist has generally regarded as “Father of Plant Science.” Theophrastus had the advantage of being able to work with Aristotle in the latter’s botanical garden at Athens, and he was able to study the structure, activities, and distribution of plants. To cut the history short, other scientists who had significant contributions to the study of plants were: Pliny the Elder (A.D. 23-29) for his work on “Natural History,”- a compendium of facts and fancies of living things that served as a storehouse of botanical information; Dioscorides for studying plants for their medical properties that brought botany and medicine together; Croateus (1st century B.C.), as Father of “Botanical Illustrations;” Herbalists for their proposal in plant classification, though specific crude methods were used (Leonard Fuchs – 1501-1566; Garpard Bauhin – 1560 – 1554; Otto Brunfels – 1464 – 1534). The Herbalists are generally regarded as the founders of Modern Botany. They were primitive in the scientific ideas, but some of them maintained the remarkable “Doctrine of Signature,” which states that the Creator has placed a definite sign…each kind of plant indicates how it should be used in medicine…thus heart-shaped leaves were thought to be useful in heart diseases, etc. Module I  5 Modern botany talks about genes, apart from taxonomy and breeding. For a more detailed history, you may visit the Wikipedia site Botany. General Botany, as a subject, comprises the study of plants, with emphasis on flowering plants. There are two significant scopes of botany: the pure and the applied botany. These scopes will help you determine the different aspects of studying plants. A. Pure Botany – the study of plants for their interesting intrinsic features of structures and behavior for the sake of knowledge. 1. Morphology – study of forms and structure. 1.1 gross morphology – study of the external structure of plants 1.2 anatomy – study of the internal structure of plants 1.3 histology – study of plant tissues 1.4 cytology – study of cells 1.5 embryology – study of progressive changes in the form and structure from fertilization to embryo formation. 2. Systematic Botany – study that deals with the classification of plants according to their natural relationships. 2.1 taxonomy – deals with the classification of extant plants 2.2 paleobotany – study of the classification of extinct plants 2.3 phytogeography – study of the distribution of plants on earth 2.4 ecology – study of plants in relation to the environment 2.5 physiology – study of life processes and functions of the parts of the plant body B. Applied Botany – study of plants for economical, commercial, and practical value 1. Agriculture – study of the production of food. 1.1 agronomy – study of field crops 1.2 pathology – study of plant diseases and how to control them 1.3 genetics or plant breeding – study of heredity and variations for the improvement of plants 2. Forestry – study of production and conservation of wood. 2.1 wood technology – study of wood usage 2.2 silviculture – study of production/growing of forest trees 3. Pharmacognosy – deals with the collection, preservation and classification od medicinal plants 4. Horticulture – deals with the cultivation of orchard and garden plants Module I  6 4.1 pomology – study of fruits 4.2 olericulture – study of vegetable crops 5. Landscape Architecture – study of the beautification of the surface of the earth. 5.1 floriculture – study of the cultivation of ornamental/flowering plants 6. Phycology/Algology – study of (green) algae Life has never been defined in a way satisfactory to all those concerned with its definition. An admittedly imperfect description used commonly by a biologist is that life is the sum total of those phenomena exhibited by organisms. Organisms, including plants, possess a combination of the following abilities which distinguish them from non-living entities: 1. The power of ASSIMILATION or the ability to convert non-living materials into substances (protoplasm) with its characteristics, specific molecular arrangement. Assimilation can be illustrated in the picture below. Module I  7 2. IRRITABILITY – or the ability to react to the environment. In the given example, the plant shoot responds positively to the sunlight, so there is bending towards the light. 3. The power of REPRODUCTION of similar offspring. Plants undergo sexual and asexual means of reproduction Module I  8 4. The power of REORGANIZING organic molecules known as food with the release of energy, which is used in the performance of all physiological processes. (METABOLISM) 5. The power to increase in size – GROWTH Module I  9 6. Plants perform vital activities such as respiration, digestion, photosynthesis, and assimilation. 7. The bodies of plants are composed of structural units called the cell, each of which consists of a tiny mass of living substance or protoplasm. Module I  10 8. Adaptation to the environment. Now let us discuss the differences between plants and animals. Listed below are the noticeable differences in how plants differ from animals. Differences that Distinguish Plants and Animals 1. Plants manufacture their own food (through photosynthesis); animals depend on plants for food. 2. Plants contain cellulose in their structural framework (cell wall); animals don’t have cellulose, and they don’t have any cell wall. 3. Most plants contain green pigment (chlorophyll); animals don’t. 4. Most plants are stationary (sessile-cannot move from one place to another); animals are capable of locomotion. 5. Plants have an unlimited scheme of growth because of the meristematic tissues (actively dividing cells found at the tips of roots and shoots) and remain active throughout life; growth in animals is limited or determinate. Module I  11 6. Plants produce spores (nonsexual reproductive cells) that animals lack. 7. Response (to stimulus) in plants is slow, while animals show a higher degree of sensitivity. Module I  12 Lesson 2 Hello, once again! Our topic for this lesson is on the origin and evolution of plants. Do you have any idea which plant groups were the first to exist? The study of grouping, naming, and classification of plants called taxonomy, was used in the first steps of coming up with these groupings. However, a more modern approach was also used, that is, plant systematics, which encompasses taxonomy but putting evolution in the process. The following tree represents the lines of evolution, on which groups of plants occurred first and how they are related to other groups of plants. Phylogenetic tree showing the major clades (lines of evolution). The diagram was based on the symbiogenetic origin of plant cells and the phylogeny of algae, bryophytes, vascular plants, and flowering plants. (source: Wikipedia, Evolutionary History of Plants) Module I  13 In the tree, you will find the green plants at the base, then followed by the land plants. It has been the green algae (named after the chlorophyll pigment found in their cellular structures, others are named brown algae, red algae, etc.) that was regarded as the ancestor of all land plants. Green algae have chlorophyll a, found in waters, have both spore and gametes (sperm and egg cells), and form a cell plate during cell division. In the genetic evidence, they have a higher percentage of similar DNA with true plants than any other algae Like all other plants, when we say alternation of generations, there are two generations involved: the sporophyte (vegetative phase) and the gametophyte (generative phase) generations. And, like all other plants, they have 4 requisites (assimilation, genetic variation, multiplication, and dispersal) to survival in their life cycles. Below is the illustration of a life cycle in Laminaria, showing the sporophyte and the gametophyte generations. Green algae assume many forms: a. Unicellular forms: e.g., Chlamydomonas b. Motile colonies: e.g. Eudorina, Pandorina, Volvox c. Filamentous body: e.g. Oedogonium, Ulothrix d. Laminar form: e.g. Ulva e. Coenocytic or siphonous body: e.g., Acetabularia, Derbesia f. Parenchymatous form: Chara Module I  14 Common examples of green algae found in the market are Ar-arosip and Puk-puklo. Representative green algae and algal forms From complete submersion to water to living on land, plants need some adaptations in order for them to survive. The first land plants need to be near a water source, they were small but were successful in living on land. Together with the other land plants, they were able to live on land because of the following adaptations: 1. Apical meristems 2. Alternation of generations 3. Walled spores produced in sporangia 4. Multicellular gametangia 5. Multicellular, dependent embryos Other Adaptations include: 6. Cuticle 7. Secondary compounds 8. Roots 9. Shoots – stems and leaves to make foods 10.Stomata – opening in the leaf surfaces to allow a gas exchange for photosynthesis and to regulate water loss 11.A vascular system that transports food and water from roots to shoots and vice versa APICAL MERISTEMS Like I mentioned in Lession 1, apical meristems are found in the tips of roots and shoots. These meristems are actively dividing cells that supply new cells on both the roots and the shoot structures and makes the plant grow continuously. Module I  15 ALTERNATION OF GENERATIONS This involves the sporophyte and gametophyte generations. Generations could be isomorphic or heteromorphic, that is, if they are isomorphic, both the sporophyte and gametophyte show no distinct characteristics from each other. Heteromorphic generations would mean the sporophyte differs with the gametophyte both in structure and function. The sporophyte is diploid (2n), divides by meiosis to form spores. The spores are haploid (n) cells that can grow into a new, multicellular haploid organism, the gametophyte, without fusing to another cell. The gametophyte, on the other hand, is haploid (n), divides by mitosis, to form the gametes: egg and sperm. Egg and sperm fuse to form the diploid zygote, which divides by mitosis to form the sporophyte. Module I  16 WALLED SPORES PRODUCED IN SPORANGIA The spores are formed from the sporangia, and these are protected by walls inside the sporangia. The wall is called sporopollenin and serves to protect the spores from harsh environmental conditions. MULTICELLULAR GAMETANGIA The gametangia are the receptacles for the sex cells. They are either generally known as gametangia (gametangium, singular) or specialized into a female (archegonium) or male (antheridium) gametangia. The female gametangia house the egg cells that will, later on, be fertilized by the sperm cell, and the resulting zygote will be nourished in the multicellular female gametangia. Module I  17 MULTICELLULAR, DEPENDENT EMBRYOS The resulting cell from the fusion of sperm and egg inside the archegonium is the zygote. The zygote undergoes division until it becomes an embryo. The embryo takes nourishment from the archegonium until it grows into a sporophyte plant. CUTICLE The outermost layer of a primary plant body is the epidermis. This epidermis is covered by a layer of secretion from cutin and forms cuticle. The cuticle is preventing excessive loss of water (desiccation tolerance). SECONDARY COMPOUNDS Plants have metabolites in their cells that regulate metabolic activities. These are important in the plant’s survival. They are directly involved in the growth and development of the plant, whereas the secondary compounds are by-products of the primary compounds that are often used for defense purposes and give plants characteristics such as color. They are also used in signaling and regulation of the primary metabolic pathways. Resins Module I  18 Examples of these are flavonoids, terpenoids, phenolics, nitrogen-containing alkaloids, and sulfur-containing compounds. ROOTS Roots are the anchorage structure of plants, also crucial in getting water and minerals from the soil. The uptake of water and dissolved minerals hydrate the plants and are able to grow and produce food since water is an essential raw material for photosynthesis. SHOOT The shoot is found at the opposite end of the root. It bears the vegetative (stems, leaves, buds) and the reproductive (flowers) structures of the plant, thereby making the plant successful on living on land. Module I  19 STOMATA These are the structures usually found abundant in the underside of the leaves. These are responsible for the gas exchange where Carbon Dioxide enters and Oxygen leaves the plant. The counterpart of this structure in the mature stems are lenticels. They are tiny raised pores on the dermal portion of the stem. VASCULAR SYSTEM These are the xylem and phloem conducting tissues, which are usually found in vascular plants. The xylem conducts water upward from roots to shoot while phloem conducts food from “sugar source” (usually leaves or other green parts of the plant) to “sugar sink.” Both xylem and phloem are important in the production and transport of food. Module I  20 THE LAND PLANTS: THE NONVASCULAR PLANTS The first plants that moved to land are the nonvascular plants (embryophytes). These are the mosses, liverworts, and hornworts. They are called nonvascular plants because they do not have the vascular bundle (xylem and phloem) in their roots, stems, and leaves. How were they able to survive when they do not have the vascular tissues? Mosses (bryophytes), liverworts (hepatophytes) and hornworts (anthoceratophytes) live on moist surfaces. They are small plants that are sometimes ground-hugging and take water from the surroundings by capillary movement. The nonvascular plants: Mosses (L), liverworts (center), hornworts (R) Module I  21 The gametophyte generation is assimilative and is the photosynthetic structures of the plant. The sporophyte generation grows from the female gametophyte and depends on the gametophyte for nutrition. Both sporophyte and gametophyte are almost the same in size. THE LAND PLANTS: THE VASCULAR PLANTS The vascular plants are so-called vascular because they have vascular tissues: xylem and phloem. The sporophytes are branched and are independent of the gametophyte parent. There are two lines of evolution for the first vascular plants. These are the (a) Rhyniophytes and the (b) Zosterophyllophytes. These two lines are now extinct. Rhyniophytes gave rise to ferns and seed plants, while Zosterophyllophytes gave rise to lycophytes. Characteristics of Rhyniophytes and Zosterophyllophytes Rhyniophytes Zosterophyllophytes Sporangia location terminal lateral dehiscence along the side across the top Protoxylem endarch exarch We have two groups of vascular plants: A. the seedless or lower vascular plants (ferns and allies) and B. the seed plants (gymnosperms and angiosperms). Lower vascular plants are also called vascular cryptogams because they do not produce seeds. They like shady areas, and most of them have a powerful Module I  22 means of multiplication by asexual means (use of rhizomes (pointed) – underground stems). The gametophyte generation are usually smaller than the sporophyte generation. The sporophyte is the assimilative and photosynthetic structures, and the leaf-like structures are called fronds, especially in ferns. The sporangia that produce the spores are clustered under the frond, and they are called sori. In many genera, sori are protected by a flap of tissue called the indusium. Other members are Psilotum, Equisetum, Lycopodium, Selaginella, and many ferns. Terrestrial Adaptations of Seed Plants 1. Seeds replace spores as a means of dispersal 2. Gametophytes became reduced and retained within the reproductive tissue of the sporophyte 3. Heterospory Module I  23 4. The zygote develops into embryo packaged with a food supply within a protective seed coat 5. Pollen and pollination freed plants from the requirement of water for fertilization 1. Seeds replace spores as a means of dispersal The sporophyte retains its spores within the sporangia, and the tiny gametophyte develops within the spore. The ovule is the unripe seed. After fertilization, the ovule becomes the seed. The seed will now contain the sporophyte embryo plus the food supply (mature ovule tissues). 2. Gametophytes became reduced and retained within the reproductive tissue of the sporophyte. 3. Heterospory Heterospory means the male and female gametophytes are separate. The old way is that the sporangia bear the spores that would become bisexual gametophyte. The antheridia bear the sperm, and the archegonia bear the egg. In a new way, the microsporangia bear the microspores that will become the male gametophyte, which later produces the sperm. 4. The zygote develops into embryo packaged with a food supply within a protective seed coat Megasporangia are protected by layers of tissue called integuments. The ovule is inside the embryo sac. After fertilization, the embryo develops, and the ovule becomes the seed. Module I  24 5. Pollen and pollination freed plants from the requirement of water for fertilization The microsporangia bear the microspores that will become the male gametophyte, which later produces the sperm. Sperm is found in the pollen grains, and fertilization of the egg by the sperm is accomplished after pollination. Pollination, the transfer of pollen grains from stamen to the stigma of a flower, will lead to the fertilization process. The pollen grain germinates and produces the sperm cells that will be released in the micropyle of the embryo sac. This process freed the requirement for the fertilization process. THE LAND PLANTS: THE SEED PLANTS This topic will introduce you to the higher vascular plants, also known as the seed plants: the gymnosperms and the angiosperms. Gymnosperms are seed plants that do not bear flowers. Instead, they bear cones, both seed cone and pollen cone. Gymnosperms are those plants with “naked ovules,” that is, ovules located in the sporophylls, not enclosed in carpels. Module I  25 The extinct group called progymnosperms evolved from Trimerophytes, which later gave rise to conifers, cycads, and other gymnosperms. Like ferns and horsetails, progymnosperms also developed megaphyllous leaves. However, another feature was as significant – the evolution of vascular cambium with unlimited growth potential and capable of producing both xylem and phloem. Vascular cambia had also arisen in lycophytes and arthrophytes, but in both cases, there was no radial longitudinal growth. Gymnosperms evolved first, and angiosperms evolved from the gymnosperms. The sporophylls are rolled together to form the ovaries. Module I  26 Evolution of Seeds Gymnosperms have 4 phyla: 1. Ginkgophyta (Ginkgo biloba) 2. Cycadophyta (cycads) 3. Gnetophyta (Gnetum) 4. Coniferophyta (pine tree) The needle-shaped leaves were important to reduce water loss during drought. Microspores are carried by wind and dropped into the megasporangiate cone (wind-pollinated). Here are some examples of gymnosperms: Welwitschia sp. A cycad Ginkgo biloba Pinus sp. Module I  27 The life cycle of a conifer Angiosperms have only one phylum, the Magnoliophyta. Formerly, there were only 2 classes (monocots and dicots). Now there are 4 clades (evolutionary lines): 1. Basal angiosperms, 2. Magnoliids, 3. Monocots, and 4. Eudicots. The evolutionary success of angiosperms is due to the following: the flowers, fruits, endosperm, the herb, vessels, and sieve tubes, and vegetative regeneration. Let us discuss one from the other. Flowers are unique among angiosperms. They function in precise pollen transfer, and whose coevolution and alliance with insects as agents of pollen transfer led to the origin of many species for survival in one or more habitats. Fruits protect the seeds and aid in the dispersal. The endosperm is a specialized triploid tissue in the seed with nutrients and growth-promoting hormones for the rapid vigorous growth of the embryo. Module I  28 The herb is a non-woody plant that matures quickly to produce itself in a matter of months. If we compare an herb to a tree, a tree grows slowly for years before these can reproduce. It is the rapid life cycle of herbs that results in many generations of plants per unit of time. As for the vessels and sieve tubes, they are the large water and food-conducting tubes that are capable of rapid transport and mobilization of materials when the need for growth of buds, cambium, leaves, or developing fruits and seeds. Then the vegetative regeneration. This is the ability of the vegetative parts of the plant (stem, roots, and leaves) to regenerate whole new plants and provides a fast way to maintain and renew the population. Module I  29 Stem vegetative reproduction Leaf vegetative reproduction Module I  30 Here is an illustration of a generalized life cycle of an angiosperm. Module I  31 Lesson 3 Hi! I am back! Today, we will discuss lesson 3, plant diversity, and adaptations. This topic will give you a lot of terminologies that are more appropriate to use when you discuss plant diversity and plant adaptations. So, do you have any idea what diversity means? How about adaptation? Diversity means variation. There are four (4) types of plant diversity: 1. Based on habitat 2. Based on habit 3. Based on the nature of stem 4. Based on life span 1. Plant diversity based on habitat Plants are very much diverse. They can be found in any habitat. Habitat is the place where plants live. So according to this basis of plant diversity, we have the following plants: a. Hydrophytes – also known as water plants or aquatic plants; they are the green algae. They are the plants that grow near or submerged in water; have a weak root system; have a soft stem; the bulk of the tissue is spongy provided with air spaces. These plants may be (i) submerged like the Hydrilla; (ii) free-floating, and fixed floating like Salvinia, Lemna, Azolla; and (iii) amphibious (only partly submerged) like Limnophylla, Sagittaria. Two angiosperms are also marine: the Zostera and Thalassia. b. Hygrophytes – are plants that are stunted in growth and occur in moist and shady habitats. They have stems and roots that are soft and spongy. The leaves are well-developed, provided with stomata. Typical examples are begonias, ferns, aroids, and certain grasses. c. Halophytes – are plants that grow in saline soil or saline water with a relative tolerance to a high concentration of salts (NaCl, MgCl2, and MgSO4). They have pneumatophores that are negatively geotropic Module I  32 breathing roots. Common examples of these plants are mangrove vegetations like Rhizophora, Ceriops, and Avicennia. d. Mesophytes – are plants that grow in the moderate water supply. They are usually large and fast-growing, with well-developed roots and leaves. The stems may be herbaceous or woody. Majorities of angiosperms are mesophytes. e. Xerophytes – are plants that grow in xeric or dry conditions or where water availability is negligible. Examples are Euphorbia, Acacia, Amaranthus, Nerium, etc. Most xerophytes store their water in stems (Opuntia), leaves (Aloe, Agava, Bryophyllum) or in roots (Asparagus) and called succulents. f. Epiphytes – are plants that grow on the trunk or branches of other plants such as an orchid. They are considered as space parasites. However, the interaction between the orchid (commensal) growing on a tree (host) would be an example of commensalism where the host is unharmed, while the commensals benefit. g. Parasitic plants – those that live on other plants as parasites (they harm the host plant). Example: Cuscuta, Striga (grows on roots of jowar). 2. Plant diversity based on habit Plants classified on the basis of habits like shape, size, and form are the angiosperms. They are classified into four groups: a. Herbs (Herbaceous) – the stem is green, delicate, and short. The life span is short. In some, the underground part of the stem is significantly reduced, but the aerial branch with flowers at the top arises from the underground parts during reproduction. The stem of such is called a scape. E.g., onion b. Shrubs (Shrubby or Fruticose) – woody, branched, and larger than herbs. They have several stems, but there is no central axis. E.g., rose c. Trees (Arborescent) – lengthier or larger than shrubs, hard and woody, very well developed, and thick. They have a prominent trunk. Types: c.1 Caudex – stem is unbranched and usually bears a crown of leaves at the apex. E.g., date palm c.2 Excurrent – the lower part of the stem is thicker and gradually tapers above. The plant appears conical due to the acropetal arrangement of branches on the main stem. c.3 Deliquescent – the apical bud of the main stem dies after some time, and branches and sub-branches spread in different directions. E.g., Tamarindus, Ficus Module I  33 d. Culms - the nodes and internodes are incredibly prominent. Internodes are usually hollow. E.g., bamboo 3. Plant diversity based on the nature of stem a. Erect – these are the plants that grow upright. Most trees, shrubs, and some herbs possess this kind. They are characterized by a strong stem (axis) and thus can stand erect on the soil. b. Creepers – these are the plants that have a trailing stem and have roots throughout its length. They have a weak, long, and thin stem. Leaves emerge from nodes. Adventitious roots ascend from nodes throughout the length of the stem. E.g., Cynodon, Oxalis c. Trailers – are plants with stem sprawling on the ground with the help of adventitious roots. They are like creepers but differ in the adventitious roots because they do not arise from nodes. A trailer may be procumbent (stem lies completely horizontal like Basella) or decumbent (apical part is raised above the ground like Lindenbergia). d. Climbers – these plants with weak stems climb on some support by means of tendrils, petioles, spine, or adventitious roots—E.g. pea, betel, etc. 4. Plant diversity based on life span a. Ephemerals – are plants that complete their life span within a noticeably short time before the onset of actual dry conditions. These are not considered as true xerophytes and are often called as drought evaders or drought escapers. E.g., Argemon Mexicana, Solanum xanthocarpum b. Annuals – they complete their life cycle within one year and die after producing seeds. E.g., wheat, rice c. Biennials (or Biannuals) – these plants complete their life cycle in two years. The first-year shows vegetative growth and, in the second year, develop flowers, fruits, and seeds. E.g., radish, carrot d. Perennials – plants that live for many years. Most perennials bear flowers and fruits after attaining maturity in a season each year. These are the polycarpic (e.g., coconut, mango); some are monocarpic, they bear fruits once in their life (e.g., bamboo, Agave). All annuals and biennials are monocarpic. It is also important to know that angiosperms show considerable variation in size. The rootless aquatic Wolffia, smallest angiosperm, has a diameter of 0.1 mm. Aquatic Lemna, on the other hand, has a diameter of 0.1 cm. The tallest angiosperm plant is Eucalyptus regnans, which is over 100 meters tall. Most Eucalyptus trees attain a height of 130 meters. The largest-sized plant is Ficus bengalensis, spreads over an area of 2 – 5 acres with more than 20 prop roots. Module I  34 What an overwhelming information on how diverse plants are, right? Now we shall discuss adaptations. When we say adaptation, this is the adjustment or alteration in physiology, behavior, and even in the structures of an organism to develop suited to an environment. Adaptation is a term derived from the Latin word “adaptare” which means “to fit.” Plants also adapt to help them live and grow in different areas These adaptations might make it exceedingly challenging for the plant to survive in a different place. This describes why specific species of plants are found in one geographical area, but not the other. For example, you would not see a cactus living in the Arctic, nor would you see lots of tall trees in grasslands. What could be the reasons why plants adapt? We might as well ask the question, what do plants need to survive? Plants need the following: sunlight, carbon dioxide, water, the right temperature, protection, and reproduction. There are two types of adaptations in plants: structural and behavioral. When we say structural adaptation, this is the way something is built or made, while behavioral adaptation is the way something acts naturally or by instinct. Structural adaptation Behavioral adaptation Adaptations to Stems and leaves absorb Plants lean or grow towards get food energy from the sun the sun; roots grow down into soil; vines climb up trees to catch sunlight; plants like Venus flytrap, trap insects for food. Adaptations to Roots absorb water and Desert flowers can stay get water and nutrients from the soil dormant for months, only nutrients coming to life when it rains. Adaptations Vivid-colored flowers with Plants disperse seeds to grow for nectar attract pollinators new offspring reproduction such as bees, birds, and insects; sweet fruit attracts animals that spread seeds far away; some seeds are shaped to catch the wind Adaptations Spines and thorns protect for defense plants from predators; poison ivy and poison oak have toxins that give predators a painful, itchy rash Module I  35 We also have plant adaptations for different biomes like a desert, grassland, tundra, rainforest, and temperate forest. Plants in the desert have small leaves or spines to conserve water. Their thick waxy skin holds in water, and their roots near the soil surface soak up rainwater quickly before it evaporates. Grassland adaptations include having deep roots to survive prairie fires, narrow leaves (lose less water than broad leaves), and flexible stems. Tundra plants are small plants that grow near the ground earth for warmth. Dark-colored flowers captivate heat from the sun. Their fuzzy stems provide protection from wind. For rainforest adaptations, barks that are smooth and slippery keep vines from killing the trees. Slide shaped leaves do not allow the fungus to grow on plants and lets rain run off too. Temperate forest adaptations. Trees with thick barks and dropping leaves conserve water and nutrients during cold winters. Water adaptations. Flexible stems move with water currents. Floating seeds spread offspring. Below are some areas of the adaptations plants have to live in: Deserts Grasslands In water Taiga Tropical rainforest Desert plant adaptations Succulents are plants that store water in their stems or leaves. Most of them have no leaves or only have small seasonal leaves that grow after it rains. The lack of leaves helps them lessen water loss during the process of photosynthesis. Leafless plants, on the other hand, conduct photosynthesis in their green stems. Long root systems allow them to spread out wide or go deep into the ground to absorb water. Leaves with hair serve as a shade to the plants, and aids in reducing water loss. Some plants have leaves that regularly turns throughout the day to expose only a minimum surface area to the heat. The presence of spines discourages animals from eating plants for water; waxy coating on stems and leaves helps reduce water loss. Slow-growing plants Module I  36 require lesser energy. The plants do not have to create ample food and therefore do not lose as much water. Temperate grassland plant adaptations For the duration of a fire, while most of the above-ground portions of grasses perish, the roots are adapted to survive and sprout again. Some prairie plants have thick bark that resists fire, whereas their roots extend deep into the ground to captivate as much water as they can. The extensive root systems they have to prevent them from grazing animals and from pulling roots out of the land. Prairie grasses are characterized by narrow leaves that lose less water than broader leaves. Grasses grow near their base and not from their tips, and are thus not permanently damaged from the fire of from grazing animals. Most grasses take advantage of windy conditions for them to be exposed and are wind-pollinated. Also, soft stems enable them to be resilient and bend in the wind. Module I  37 Taiga plant adaptations Many trees in Taiga are evergreen so they can photosynthesize quickly when temperatures rise. These trees have needle-like leaves, whose shape loses less water and more easily sheds snow than broad leaves. The waxy coating on needles prevents excessive evaporation. Needles have dark colors allowing more solar heat to be absorbed. Many trees have branches that droop downward to help shed excess snow to keep the branches from breaking. Plant adaptation in water Flexibility is an adaptation for underwater leaves and stems, allowing them to move with water currents for faster dispersal. There are plants that Module I  38 have air spaces in their stems that aid them in being up in the waters. Submerged plants, on the other hand, lack a strong water transport system (in stems); instead, water, nutrients, and dissolved gasses are absorbed through the leaves directly from the water. Roots and some root hairs are reduced or absent; roots only needed for anchorage, not for the absorption of nutrients and water. Other plants have leaves that float atop the water, exposing themselves to the sunlight. In floating plants, chlorophyll is restricted to the upper surface of leaves (the part that the sunlight will hit), and the upper surface is waxy to repel water. Some plants produce seeds that can float. Tropical rainforest plant adaptations Waxy surfaces and drip tips and allow water to run-off, to discourage the growth of fungi and bacteria. Buttresses, prop, and stilt roots hold up plants in the shallow soil. Some plants also climb and cling on others to stretch towards the sunlight. Flowers on the forest floor are designed to lure animal pollinators since there is relatively no wind on the forest floor to aid pollination. Smooth bark and smooth, waxy flowers speed the run-off water. Plants contain shallow roots to help capture nutrients from the top level of the soil. Many bromeliads are epiphytes; instead of collecting water with roots, rainwater is collected into a central reservoir where they absorb the water through leaf hairs. Epiphytic orchids contain aerial roots that cling to host plants to absorb minerals and absorb water from the atmosphere. Module I  39 Lesson 4 Hello, once again! How is your reading? This time, we will review the domains of life. Below is the diagram of the three (3) domains coming from a common ancestor with the derivatives for each of them. This three-domain system was introduced by Carl Woese et al. in 1990, and it divides cellular life forms into archaea, bacteria, and eukaryotic domains. In the old classification, especially in the 5-kingdom scheme, Kingdom Monera houses the prokaryotes, which include bacteria. In this 3-domain system, members of Kingdom Monera were split into Domain Archaea and Domain Bacteria, leaving the eukaryotes into a single domain, the Eukarya. Woese argued that bacteria, archaea, and eukaryotes differ in their 16S rRNA genes, and each arose separately from a common ancestor. The term “domain” was adopted in 1990. The three-domain is “above” the Kingdoms present in the five- or six-kingdom systems. A phylogenetic tree on the next page will show you the members of each of the domains, followed by sample pictures for each domain. Module I  40 A phylogenetic tree based on rRNA data, emphasizing the separation of bacteria, archaea, and eukaryotes, as proposed by Carl Woese et al. in 1990 The three-domain system includes the Archaea (represented by Sulfolobus, left), Bacteria (represented by S. aureus, middle), and Eukarya (represented by the Australian green tree frog, right). Pictures are taken from Wikipedia Domain Archaea The archaea are prokaryotic, with no nuclear membrane, distinct biochemistry, and RNA markers from bacteria. They possess unique, ancient evolutionary history for which they are considered some of the oldest species on Earth. They feed on inorganic matter and live in extreme, harsh environments. Some examples are the: ⮚ Methanogens – which produce the gas methane ⮚ Halophiles – live in very salty water ⮚ Thermoacidophiles – thrive in acidic, high-temperature water Module I  41 Domain Bacteria Bacteria are also prokaryotic, with cells containing rRNA, but with no nuclear membrane, their membranes have diacyl glycerol diester lipids. Many thrive where humans are, and they were the first prokaryotes discovered. Most known pathogenic prokaryotic organisms belong to bacteria, they are more extensively studied than the archaea. Some examples are: ⮚ Cyanobacteria – otherwise known as blue-green algae, are photosynthesizing bacteria that are related to the chloroplasts of eukaryotic plants and algae ⮚ Spirochaetes – gram-negative bacteria that include those causing syphilis and Lyme disease ⮚ Actinobacteria – gram-positive bacteria including Bifidobacterium animalis which is present in the human large intestine Domain Eukarya This domain contains the eukaryotes. Their cells contain a membrane-bound nucleus, and their organelles are all enclosed by membranes. Members of this domain are: Kingdom Protista – are either unicellular or unicellular-colonial microscopic organisms. Kingdom Fungi – include yeasts and molds ⮚ Saccharomycotina – includes true yeasts ⮚ Basidiomycota – includes mushrooms Module I  42 Other examples of Kingdom Fungi Kingdom Plantae – our concern, the plants Kingdom Animalia – the animals Module I  43 Lesson 1 is about the nature of botany and plants, also discussing the differences between plants with animals. Lesson 2 is on the origin and evolution of plants, discussed here are the characteristics of the different groups of plants, including the green algae, the adaptations made by plants living on land, and some complete life cycles of gymnosperms and angiosperms were shown. Lesson 3 is about how diverse plants are and the different adaptations they must get food, water, and nutrients, reproduction, and defense. Lesson 4 showed the three-domain system in the classification of organisms above the kingdom level. Congratulations! You have just studied Module I. Now, you are ready to evaluate how much you have benefited from your reading by answering the summative test. Good Luck!!! 1. Based on your readings in your module, what are the best characteristics of plants in general? 2. Differentiate pure and applied botany. 3. Can you single out the best features for the following plants? a. Green algae b. Nonvascular plants c. Lower vascular plants d. Gymnosperms e. Angiosperms 4. How would you distinguish plants and animals? 5. Name the 3 domains and describe the types of organisms in each. Which are the prokaryotes? Module I