Ahfad University for women Biology 121 Lesson 1: Plant Morphology PDF

Ahfad University for women Biology 121: Part one: Plant morphology Lecture one: A View of Life How to Define Life: Biology is the scientific study of life. There is great diversity among living thin gs. Living things are comp...

Ahfad University for women Biology 121: Part one: Plant morphology Lecture one: A View of Life How to Define Life: Biology is the scientific study of life. There is great diversity among living thin gs. Living things are composed of the same chemical elements as nonliving thin gsobey the same physical and chemical laws that govern everything in the unive rse. Because life is so diverse, it seems reasonable that it cannot be defined in a straightforward manner. Instead, life is best defined by several basic characteris tics shared by all organisms. Characteristics of life : 1- Living things are organized: The levels of biological organization range from atoms to the biosphere. The cell is the basic unit of structure and function of all living things they can be unicellular or multicellular. Each level of organization is more complex than the level preceding it as biological complexity increases. 2. Living things acquire materials and energy: Energy is the ability to do work. Energy is required to maintain organization and conduct life-sustaining processes such as chemical reactions. Metabolism is all the chemical reactions that occur in a cell. The sun is the ultimate source of energy for nearly all life on Earth. Plants, algae, and some other organisms capture solar energy and perform photosynthesis. Photosynthesis is a process that converts solar energy into the chemical energy of carbohydrates. 3. Living things maintain homeostasis: Homeostasis is the maintenance of internal conditions within certain boundaries. Ability to maintain a state of biological balance. Feedback systems monitor internal conditions and make adjustments. 4. Living things respond to stimuli: Living things interact with the environment and respond to changes in the en vironment.The ability to respond often produces movement 5. Living things reproduce and develop: All living organisms must reproduce to maintain a population. The manner of reproduction varies among different organisms. When organisms reproduce, they pass on copies of their genetic information (genes) to the next generation. Genes determine the characteristics of an organism. Genes are composed of DNA (deoxyribonucleic acid). 6. Living things have adaptations: An adaptation is any modification that makes an organism better able to function in a particular environment. The diversity of life exists because over long periods of time, organisms respond to changing environments by developing new adaptations. Organizing Diversity Taxonomy: is the branch of biology that identifies, names, and classifies organ isms. Systematics: is the study of evolutionary relationships between organisms. Classification categories:  From least inclusive category (species) to most inclusive category (domain): Sp ecies, genus, family, order, class, phylum, kingdom, and domain. Each successive c ategory above species includes more types of organisms than the preceding one. All living organisms are classified into three domains: 1- Archaea Domain ◦ Contains unicellular prokaryotes that live in extreme environments  Prokaryotes lack a membrane-bound nucleus. 2- Bacteria Domain ◦ Contains unicellular prokaryotes that live in all environments 3- Eukarya Domain ◦ Contains unicellular and multicellular eukaryotes ◦ Eukaryotes contain a membrane-bound nucleus.  Lecture 2: External Features of flowering plants Flowering plants have bodies consisting of two parts which live under differ ent conditions. One part is aerial exposed to sunlight, and called shoot system; t he other part is embedded in the soil and known as root system. The root syste m grows vertically downwards in the opposite direction to that taken by the sho ot system. This main root may bears side branches which further produce lateral roots spreading out in all directions. The shoot system has a main axis, the stem, carr ying branches. The lateral branches arise in the axils of leaves. Branches carry l eaves, buds and flowers. The part of the stem from which a leaf arises is called a node, while the portion between two successive nodes is called internode.  The stem and its branches carry food materials up and down and elevate th e green parts (leaves) to the sunlight to carry out photosynthesis and expose flo wers to pollinating agents. The leaves usually called foliage leaves and are arranged on the stem or branches. The typical leaf consists of three parts, the leaf base, petiole and flattened green lea f-blade or lamina. The leaf has a main vein extending from the base to the tip of th e lamina known as midrib. From this midrib arise a number of lateral veins which branch further to form a reticulate venation (in dicot plants). The size of the plant varies considerably. 1) Herbs: Those plants whose stems develop a small amount of wood and remain soft. 2) Shrubs: they develop short and much branched, with erect woody stems. 3) Trees: develop tall, woody. erect stems growing to a large size. Regarding the length of life plants are divided into: 1) Annuals: Plants that complete their whole life from seed to fruit in one year or less. 2) Biennials: completing their life cycle in two years. 3) perennials: extend for more than two years. According to environmental conditions plants are classified into: 1) Xerophytes: live in scarcity of water e.g., desert plants. 2) Mesophytes: live in medium conditions e.g., wheat. 3) Hydrophytes: live in abundance of water e.g., Eichornia spp Flowering plants are classified into two main groups: 1) Dicotyledonous (Dicot). -Have two cotyledons in the seed embryo. -Reticulate leaf venation. -Tap root system. 2) Monocotyledonous (Monocot). -Have one cotyledon in the seed embryo. -Parallel leaf venation. -Fibrous root system (adventitious)  Lecture 3: Seeds and Seed Germination The seed is a mature fertilized ovule. Characteristics of the Seed: The seed has one point of attachment. Structure of the seed: The mature seed consists of: 1)The Seed coat (Testa): It is the protective wall surrounding the embryo and storage tissue. In most seeds a scar is present on the testa marking the point of attachment of the seed to the funiculus, the scar is known as the hilum. A minute pore is mostly present in the testa of many seeds it represents the micropyle of the ovule. 2)The embryo: In many seeds, the embryo is formed of a plumule, radicle and one or two cotyledons (one cotyledon-monocotyledonous plant: two cotyledons- dicotyledonous plant). 3) The Storage tissue: Some seeds possess a special storage tissue called endosperm (endospermic seeds). Those lack endosperm are called non-endospermic seeds  Embryo parts: a-Plumule: It is the terminal upper portion of the embryo which give rise to shoot system. b-Radicle: It is the terminal lower portion of the embryo, from which the primary root arises. c- Cotyledons: They are mainly concerned with storage of food which is used d uring germination because the plant is not capable of producing its own food. Seed germination is the emergence or protrusion of the embryo parts. Conditions necessary for seed germination: 1) State of the seed: These are internal conditions necessary fo seed germination include: a-Viability: The capacity of the seed to grow under favorable conditions. (Can be tested by TTC solution). b-Dormancy of the seed: A rest period needed by the seed 2) Presence of water 3) Presence of oxygen. 4) Suitable temperature. Epicotyl: It is the portion between the cotyledons and the first leaf. Hypocotyl: It is the portion between the cotyledons and the first lateral root Types of seed germination: 1) Hypogeal germination: The cotyledons remain inside the soil. a) Broad Bean (Vicia faba) Stage I: In this stage the testa is ruptured and the radicle comes out. Stage II: The radicle elongates and the plumule comes out.  Stage III: The radicle and the plumule elongate to considerable size. The root system complete and also shoot system, this stage called seedling. eal b) Hypogeal germination of Zea mays It is a fruit (grain), the testa of the seed fused with the pericarp (fruit wall). Stage I: In this stage the pericarp is ruptured and the radicle comes out through its sheath. Stage II: The radicle elongates and the plumule comes out enclosed by coleoptile. Stage III: Is characterized by emergence of the foliage leaves. Radicle is replaced by developing adventitious roots  2) Epigeal germination: The cotyledons come above the soil. Lupinus termis Stage I: In this stage the testa is ruptured and the radicle elongates rapidly downwards. Stage II: The hypocotyl elongates and the cotyledons are pushed above the soil surface. Stage III: The independent seedling possesses a differentiated roots system and shoot system.  Lecture 4: THE ROOT The root is the descending organ of the plant, and originally is the direct prolongation of the radicle. Functions of the roots:- 1-Fix the plant to the ground. 2-Absorb water and salts from the soil. 3-Synthesize hormones necessary for plant growth. Characteristics of root: Does not has buds, leaves, flowers, nodes or internodes. Regions of root: 1) Root cap: Cover the root apex which protects the tender apex. 2) Region of cell division: The growing apex of the root, the cells of this region undergo repeated divisions (meristematic region). 3) Region of elongation. Lies above the meristematic, responsible for growth in length in the root. 4) Region of maturation: Externally at the basal portion produces root-hairs and lateral roots. Types of the root: 1) Tap roots: Develop from the radicle, consist of primary root and lateral roots 2) Adventitious roots: Do not develop from the radicle Both tap and adventitious roots when performing some special functions they get modified in various ways ( normal functions of roots are fixation and absorption of water and minerals and production of some hormones). Modified tap roots: a) Modified primary roots for storage of food: i- Conical root: When the root is broad at the base and gradually tapers towards the apex like a cone, e.g. carrot. ii- Fusiform Root: When the root is swollen at the middle and gradually tapering towards the apex and the base. e.g., Radish. iii- Napiform Root: When the root is considerably swollen at the upper part becoming almost spherical and sharply tapering towards the lower part. e.g., Beet. b) Modified Lateral tap Roots ( respiratory roots): Many plants growing in marshy places and salt lakes develop special kind of roots, called respiratory roots for respiration as in Mangroves plant (Avicennia sp.) Such roots grow from the underground roots of the plant but rise vertically upwards. )  Lecture 5:The Stem The Stem is the ascending organ of the plant, and is the direct prolongation of the plumule. Characteristics of the stem: 1- It bears buds, leaves, branches and flowers. 2- provided by nodes and internodes. Functions of the stem: 1) Bearing leaves and flowers. 2) Conduction of water and mineral salts from root to the leaf, and prepared food material from the leaf to the different parts. 3) Support branches. The bud: - A bud is a young undeveloped shoot consisting of a short stem and a number of tender leaves arching over the growing apex. In the bud the internodes not developed and the leaves remain closely crowded together forming a. Types of buds: 1)Normal: a) Apical or Terminal bud: -Grows at the apex of a stem or branch. -Leads the growth. b) Axillary bud: -Grows in the axil of a leaf.  -Gives branches. 2) Accessory buds: An extra buds develop by the side of the axillary bud. 3) Adventitious buds: Arises in any other part of the plant body. Forms of stems (habits): 1) Erect stems: Grow upright to the soil level. This may be: a) Herbaceous b) Woody 2) Weak stems: Cannot stand upright on their own and may either be: a)Twining stems: The stem twines its body around a support. e.g., Leptadenia sp. b) Climbing stems: Use special device to attach to the support. e.g., tendrils as in Antigonon sp. c) Creeping stems: Growing horizontally above the ground, have one tap root, lack adventitious roots at the nodes. e.g., Tribulus sp.  Modification of the stem: Stem or branches of certain plants are modified into various shapes to perform special functions. Types of stem modifications; 1) Underground modifications (subterranean). 2) Sub-aerial modifications. 3) Aerial modifications. Underground modifications: For the purpose of perennation stems of certain plants develop underground and lodge there permanently, lying in a dormant leafless condition for some period and then giving off aerial shoots annually under favourable conditions. They can be distinguished from roots by presence of: i. Nodes and internodes. ii. Scale leaves. iii. Buds (axillary and terminal). The main functions of underground stems are: i. Perennation. ii. Storage of food materials.  iii. Vegetative propagation. Types of modified underground stems: a) Rhizome. b) Tuber. c) Corm. d) Bulb. e) Bulbil b) Tuber: It is a swollen end of a special underground branch.The underground branch arises from the axil of a lower leaf, grows horizontally outwards and swells up at the apex due to the accumulation of food. e.g., Potato.. 2-Subaerial modifications: For the purpose of vegetative propagation some of the lower buds of the stem in certain plants grow out into long or short, lateral branches. Types of sub-aerial modifications: a) Runner. b) Offset. A) Runner: This is a slender branch with long internodes, growing horizontally on the ground surface and rooting at the nodes. The runner arises as an axillary bud and grows some distance away from the mother plant, then strikes roots and grow into a new plant. e.g., (Cynodon sp. and Strawberry). B) Offset: Like the runner, it originates in the axil of a leaf as a short branch, it elongates to some extent only The apex turns up and produces leaves aba cluster of roots below. e.g., Eichhornia sp. Aerial modifications; Vegetative and floral buds which would normally develop into branches and flowers, often undergo extreme degree of modification in certain plants for definite purposes. Typesof aerial modifications: a) Thorns for protection. b) Cladode for photosynthesis. c) Phylloclade for photosynthesis. 1) 2) 3) b) Cladode:-These are green branches of limite d growth (usually one internode long) which have taken up the functions of leaves. True leaves are reduced to scales or spines. e.g., Asparagus sp. c)Phylloclade: It is green, flattened, cylindrical stem or branch of unlimited growth, with distinct nodes and internodes.  It is thick, fleshy and succulent, as in Opuntia sp.  In xerophytes, leaves get modified into spines or get reduced in size to check the loss of water due to transpiration and thus stem takes up the function of leaf (photosynthesis)    Lecture 6:The Leaf The leaf is the flattened, lateral outgrowth of the stem or the branch. Developing from a node and having a bud in its axil. Characteristics of leaf: An axillary bud is often present in the axil of each leaf. Functions of leaf: 1) Photosynthesis (Manufacture of food). 2) Exchange of gases through stomata. 3) Evaporating of water (Transpiration). 4) Storage of food. Parts of leaf: 1) Leaf base: It’s the part attached to the stem. 2) Petiole: It’s the stalk of the leaf. When the petiole is absent the leaf is said to be sessile; and when present it is said to be petiolate. 3) Leaf- blade or lamina: It is the green, expanded portion containing a strong vein, known as the mid-rib; this produces thinner lateral veins and veinlets. The lamina is the most important part of the leaf since this is the seat of food- manufacture for the entire plant. Kinds of leaves: 1) Foliage leaves: These are the normal green leaves and very common in all plants. 2) Cotyledonary leaves: In epigeal germination he cotyledons are puhd above the soil and turn green in colour to carry out photosynthesis till the ordinary leaves are formed. 3) Prophylls: the first formed leaves of some developing seedling as in Vicia faba seedling and differ from the succeeding leaves. 4) Scale leaves: they are protective structures. They have no chlorophyll brown, red or white they are found in underground stems. 5) Bracts (attractive leaves) Changes colour to attract insects as in Bougainvellia sp. 6) Floral leaves: Like sepals and petals.  Duration of leaves: 1) Caducous: fall soon after it appears. 2) Deciduous: lasts one season (e.g., falling off in winter) 3) Ever green (Persistent). The mode of arrangement of veins in leaves. Types of venation: 1) Reticulate (Dicot plants) the main vein divides into various branches and form a net-like structure in the lamina. 2) Parallel (Monocot plants) Here all veins run parallel to each other Types of leaves: 1) Simple leaf: A leaf is said to be simple when it consists of a single blade. 2) Compound leaf: When the incision of the leaf-blade goes down to the mid-rib (rachis) or to the petiole so that the leaf is broken up into a number of segments called leaflets these being free from one another. Types of compound leaf: 1) Pinnate: Leaflets arrange laterally on the rachis. 2) Palmate: Leaflets radiate from a common point like fingers from the palm. Comperison between a compound leaf and abranch: Phyllotaxy: The mode in which the leaves are arranged on the stem or the branch. Types of phyllotaxy: 1)Alternate (spiral): A single leaf arises at each node. 2) Opposite: Two leaves arise at each node standing opposite each other. i) Superposed ii) Decussate 3) Whorled: There are more than two leaves at each node and these are arranged in a circle or whorl. Modifications of leaf: 1) Leaf-tendril. 2) Leaf spines (for defensive purpose). 3) Phyllode. 4) Bladder: In aquatic plants helps in floating. 5) Pitcher: Capture insect and digest them.  Lecture 7: The Flower The flower is a modified shoot for the reproduction of the plant. It is a collection of four different kinds of floral members arranged in four separate whorls. Parts of flower: 1- Pedicel: the stalk of the flower. 2- Thalamus: the swollen end of the axis which the floral leaves inserted on. 3-The four whorls: arranged in a definite order, one just above the other. a- Calyx: consists of a number of green leafy sepals. b- Corolla: consists of a number of usually coloured petals. c- Androecium: the male whorl, consists of a number of stamens, each stamen is made of: i-Anther (composed of four champers or pollen sacs), filled with pollen grains (male gametes). ii-Filament. d- Gynoecium (pistil): the female whorl, it’s component parts are called carpels. The gynoecium is made of three parts: i-Stigma. ii-Style. iii-Ovary containing ovules (female gametes). Androecium and gynoecium are reproductive whorls, while calyx and corolla are accessory whorls.  Some descriptive terms: Complete flower: When all the four whorls are present. Incomplete flower: When any of the four whorls is absent. Hermaphrodite flower: When male parts and female parts are present in same flower. Monoecious plants: Having separate male and female flowers on the same plant. e.g., family Cucurbitaceae. Dioecious plants: Male flowers are on one plant and female flowers are on another plant. e.g., Date-Palm. Pollination: Is the transference of pollen grains from the anther to the stigma. Types of pollination: 1) Self-pollination: Here pollination taking place within a single flower or between two flowers in the same plant. 2) Cross pollination: Pollination taking place by two separate plants. Fertilization: Is the fusion of male gametes (pollen grains) and female gametes (ovules).  Lecture 8; The Fruits The fruit is a mature fertilized ovary. Characteristics of fruits: Fruits have two points of attachments (scars). One at the apex marking remains of the style, and the other at the base where the ovary had been attached to the thalamous.. Parts of fruits: 1) Pericarp and 2) Seeds The pericarp may be thin or thick. The thick pericarps are differentiated into three regions: 1) Epicarp: It is the outermost thin layer 2) Mesocarp: The middle thick and fleshy layer which forms the pulp 3) Endocarp: The innermost layer which may be membranous or hard Functions of fruits: 1) Store food materials 2) Protect the seed 3) Help in seed dispersal Types of fruits; 1) True fruits: develop from the ovary. 2) False fruits (Pseudocarp): other floral parts, particularly the thalamus or even the calyx may form apart of the fruit e.g., Apple. Classification of fruits: There are three types of fruits based on their origin, texture and dehiscence: 1) Simple fruits 2) Aggregate fruits 3) Multiple or composite fruits  Simple fruits: It is a single fruit develops from the ovary (either of one carpel or many united carpels) of a flower with or without accessory parts. simple fruits may be: a- Dry or b- Fleshy (Succulent). The dry simple fruits may be i- Dehiscent ii- Indehiscent iii- Schizocarpic   Fleshy (succulent ) fruits: The fruits usually remain fleshy and juicy even at maturity. The pericarp is differentiated into epicarp, mesocarp and endocarp.  The Cell Structure and functions All organisms are composed of cells, which arise from pre-existing cells. There are two types of cells: 1) Prokaryotic: e.g., Bacteria, Archea. 2) Eukaryotic: e.g., Protists, Plants, Fungi and Animals Prokaryotic cells do not have a membrane bounded nucleus, nor the various membranous organelles of eukaryotic cells. Structure of Eukaryotic cells: Cell wall: Surround plant cells, shapes, supports, and protects cell Cell membrane: Immediately inside the cell wall, surrounds cytoplasm, and regulates entrance and exit of molecules Nucleus: command centre of cell and contains the genetic material. Nucleolus: produces subunits of ribosomes Cytoplasm: semifluid matrix outside nucleus that contains organelles Endoplasmic reticulum: location of protein and lipid metabolism. Ribosomes: makes protein. Mitochondria: carries out cellular respiration, producing ATP molecules for energy. Golgi apparatus: vesicle that is involved in fatty acid metabolism Vacuole: large, fluid-filled sac that stores metabolites and helps maintain turgor pressure. Chloroplasts: are only found in green plants. They are green-colored bodies that carry out photosynthesis to make sugar for the plant