MT Pharmaceutical Botany with Taxonomy 2.1-2.2 PDF

Roots & Stems OUTLINE Roots External Structures Internal Structures Other root types and modifications Stems External Structures Internal Structures Other stem types and modifications ROOTS CONCEPTS  Functions of Roots 1. Anchorage – to locate water and minerals, roots perm...

Roots & Stems OUTLINE Roots External Structures Internal Structures Other root types and modifications Stems External Structures Internal Structures Other stem types and modifications ROOTS CONCEPTS  Functions of Roots 1. Anchorage – to locate water and minerals, roots permeate the soil. In doing so, they anchor the plant in one place for its entire lifetime 2. Absorption – roots absorb large amounts of water and dissolved minerals (nitrates, phosphates, and sulfates) from the soil 3. Conduction – water and minerals upwards into the stem and food from leaves to storage regions of the roots  Functions of Roots 4. Storage – roots store large amounts of energy reserves, initially produced in the leaves of plants via photosynthesis and transported in the phloem, as sugar, to the roots for storage, usually as sugar or starch until they are needed. EXTERNAL STRUCTURE OF ROOTS The root system is the descending (growing downwards) portion of the plant axis. When a seed germinates, radicle is the first organ to come out of it. It elongates to form primary or the tap root. It gives off lateral branches (secondary and tertiary roots) and thus forms the root system. Types of Root Systems  Types of Root Systems Tap root system Fibrous root system It is the root system that In this root system, the primary develops from the radicle and root is short-lived. continues as the primary root A cluster of slender, fiber-like roots (tap root) which gives off arises from the base of the radicle lateral roots. and plumule which constitute the These provide very strong fibrous root system. anchorage as they are able to They do not branch profusely, are reach very deep into the soil. shallow and spread horizontally, It is the main root system of hence cannot provide strong dicots e.g. gram, chinarose, neem anchorage. Fibrous root system is the main root system of monocots, e.g. maize, grasses, wheat  Taproot Root System A strongly developed main root which grows downwards bearing lateral roots much smaller than itself In most dicots, the radicle enlarges to form a prominent taproot that persists throughout the life of the plant Many progressively smaller branch roots grow from the taproot Their system is called taproot system, common in dicots and conifers In plants such as carrots and sugar beets, fleshy taproots store large reserves of food, usually as carbohydrates  Taproots are modified for reaching deep water in the ground: e.g the long taproots of poison ivy (Rhus toxicodendron), dandelion (Taraxacum sp.) and mesquite (Prosopis sp.)  Fibrous Root System “Diffuse” Root System Has several to many roots of the same size that develop from the end of the stem With smaller lateral roots branching off of them 1. Most monocots (including grasses and onions) have a fibrous system 2. The fibrous roots of few plants are edible – sweet potatoes are the fleshy part of a fibrous root system 3. In these plants, the radicle is short-lived and is replaced by a mass of adventitious roots a. (from Latin – adventicus – meaning “not belonging to”), which are roots that form organs other than roots. b. Because these roots arise not from preexisting roots, but from the stem, they are said to be adventitious  TYPES OF ROOTS Adventitious root Tap root These are roots that develop from It is the primary and the any part of the plant except the main root that develops from radicle. the radicle They may be aerial or underground They may grow from node (money plant, bamboo) stem cutting (rose) tree branch (banyan) or stem base (fibrous roots in monocots) Adventitious Roots  Adventitious Roots Roots that develop in an unusual place There are several types of adventitious roots besides those of monocots a. Adventitious roots are common along rhizomes (underground stems) of ferns, club mosses (Lycopodium) and horsetail (Equisetum)  Prop roots are a type of aerial adventitious roots that are modified to provide support. They help in providing mechanical support to the aerial branches. They grow vertically downward into the soil as lateral branches and act as pillars. They are also known as columnar roots that give extra mechanical support to heavy stem branches of the banyan tree (mangrove)  INTERNAL STRUCTURE OF ROOTS 1. Root cap region 2. Region of meristematic cells 3. Region of elongation 4. Region of maturation Root cap region A thimble-like structure produced by meristematic (rapidly dividing) zone and protects the tender apex (apical meristem) from harsh soil particles. As the root grows further down in soil, root cap wears out but it is constantly renewed. In aquatic plants (Pistia and water hyacinth) root cap is like a loose thimble, called root pocket Root Apical Meristem A small region of actively dividing cells called the apical meristem. Apical is a description of growth occurring at the tips of the plant, both top and bottom. Besides the cells that divide continuously, root apical meristem contains a group of inactive cells that form the so-called quiescent center. constitutes a reservoir of cells to be used in the regeneration of damaged meristematic areas. Region of elongation This is situated next to the meristematic region, wherein, the cells elongate and enlarge to make the root grow in length. Region of maturation ROOT HAIR ZONE This is next to the region of elongation, wherein the cells mature and differentiate into various tissues constituting (i) Root hair or piliferous region having unicellular hairs which absorb water and mineral salts from the soil and (ii) Permanent region which lies behind the root hair zone and is without hairs. It produces lateral roots, anchors the plant in soil and conducts water and minerals upwards. Many of the much larger cells of the metaxylem and metaphloem become fully differentiated and functional in the zone of maturation. Within the xylem, the inner wide cells are metaxylem and the outer narrow ones are protoxylem.  Between the vascular tissue and the endodermis are parenchyma cells that constitute an irregular region called the pericycle. When lateral roots are produced, they are initiated in the pericycle. Root hairs function only for several days, after which they die and degenerate.  ORIGIN AND DEVELOPMENT OF LATERAL ROOTS Lateral roots are initiated by cell divisions in the pericycle. By the time the lateral root emerges, it has formed a root cap, and its first protoxylem and protophloem elements have begun to differentiate, establishing a connection to the vascular tissues of the parent root. OTHER TYPES OF ROOTS AND ROOT MODIFICATIONS Tap roots and adventitious roots can get modified into a variety of forms to perform various functions: Storage Roots Prop Roots Aerial Roots of Orchids Contractile Roots Mycorrhizae Root Nodules and Nitrogen Fixation Haustorial Roots  Modifications of Roots Roots sometimes have special functions to perform and in such cases their form and structure differ from those of normal roots. The modified roots may be underground or aerial. Underground Root Modifications Taproot and adventitious roots may undergo certain modifications to perform the function of storage and vegetative propagation  STORAGE ROOTS In some plants, the tap roots store reserve food for which they become swollen and different shapes. These are the types: i. Fusiform ii. Napiform iii. Conical iv. Tuberous or Tubercular v. Pneumatophores  Fusiform It is a modified tap root. The primary root is swollen in the middle while both the ends gradually taper forming a spindle shaped structure E.g radish How to Write the Scientific Name or Botanical Origin Common Name: Radish Botanical Origin (Equivalent of scientific name in plants) Raphanus sativus Raphanus is the genus and must always begin in capital letter. sativus is the specific epithet and always begins in lower case or small letter. If handwritten, underline separately: Raphanus sativus If computerized, italicize. Raphanus sativus  Napiform The hypocotyls region is considerably swollen, becoming almost spherical and then abruptly tapering towards the lower end Turnip Brassica campesteris var. rapa  Conical The roots swell, becoming broad at the base and gradually taper towards apex forming a cone like structure e.g. Carrot Daucus carota  Tuberous or tubercular In this case, the root is thick and and fleshy but does not form any definite shape E.g. Cassava Manihot esculenta  Pneumatophores › These roots grow vertically up and come out of water or marshy soil like conical spikes. They occur in large numbers around the trunk › Such roots are provided with numerous pores (breathing pores) through which air is taken for respiration. Pneumatophores Mangrove/ Black Mangrove Avicennia germinans  Prop Roots In Banyan, the adventitious roots arise from the horizontal branches and grow vertically downwards. After reaching the soil, they become thick and woody. Thus, they function as pillars giving mechanical support to the branches. Hence, they are also known as columnar roots.  Aerial Root Modifications Aerial roots are adventitious roots which develop from the aerial parts of the plant to perform various functions : For mechanical support For vital functions Aerial roots of orchids, which grow along the surface of tree bark, are covered by a white velamen that helps retain the water absorbed by the green root tip.  CONTRACTILE ROOTS In Oxalis, Gladiolus, Crinum, and other plants (many with bulbs), roots undergo even more contraction than prop roots do. Have wiry roots that pulls the bulb deeper into the soil to keep them firmly underground  MYCORRHIZAE The roots of most species of seed plants (at least 80%) have a symbiotic relationship with soil fungi in which both organisms benefit. The associations are known as mycorrhizae (sing.: mycorrhiza), and two main types of relationships are known. 1. Woody forest plants, an ectomycorrhizal relationship exists, in which the fungal hyphae (slender threadlike cells) penetrate between the outermost root cortex cells but never invade the cells themselves. 2. Herbaceous plants have an endomycorrhizal association, in which the hyphae penetrate the root cortex as far as the endodermis  The plant cells lack starch grains, presumably because the sugars are being transferred to the fungus. The fungus is unable to live without the sugars from the plant, and, in many cases, the plant is severely stunted if the fungus is killed. Apparently, this is a critical means of absorbing phosphorus into the roots, the mycorrhizal fungi being much more effective than root hairs. ROOT NODULES AND NITROGEN FIXATION For most plants, the scarcity of nitrogenous compounds in the soil is one of the main growth-limiting factors. The chemical process of converting atmospheric nitrogen into usable compounds is nitrogen fixation. In a small number of plants, especially legumes, a symbiotic relationship has evolved with nitrogen-fixing bacteria of the genus Rhizobium. ROOT NODULES AND NITROGEN FIXATION For most plants, the scarcity of nitrogenous compounds in the soil is one of the main growth-limiting factors. Although nitrogen is abundant in the air (78% of the atmosphere is N2), plants have no enzyme systems that can use that nitrogen. Only some prokaryotes can use N2 by incorporating it into their bodies as amino acids and nucleotides; when they die and decompose, the nitrogenous compounds are available to plants. The chemical process of converting atmospheric nitrogen into usable compounds is nitrogen fixation. In a small number of plants, especially legumes, a symbiotic relationship has evolved with nitrogen-fixing bacteria of the genus Rhizobium.  HAUSTORIAL ROOTS OF PARASITIC FLOWERING PLANTS  HAUSTORIAL ROOTS OF PARASITIC FLOWERING PLANTS The roots of parasitic plants have become highly modified and are known as haustoria. Parasites like Cuscuta develop a kind of root which penetrates into the tissue of the host plant and help to draw nutrients from the host by sucking it. The parasitic plants are not completely equipped to prepare their food. Hence, such plants have to depend on host plants for nutrients Transverse section of a branch of juniper being attacked by the haustorium (modified root) of a mistletoe (Phoradendron). The wood of the host juniper has been stained blue, the bark is tan. The haustorium is able to draw water and nutrients from the host vascular tissue. STEMS CONCEPTS  Functions of Stems 1. Support of plant’s main body and leaves 2. Conduct food and water 3. Stems help store water (cacti). Sweet palm (Arenga pinnata) stores large amounts of starch. 4. Young green stems perform minor roles in the production of food through the process of photosynthesis but in some species such as cacti, the stem is the chief photosynthesizing organ. EXTERNAL STRUCTURE OF ROOTS The terms "stem" and "shoot" are sometimes used interchangeably. Technically the stem is an axis, whereas the shoot is the stem plus any leaves, flowers, or buds that may be present.  Nodes- where leaves are attached Internodes-the regions between nodes leaf axil-The stem area just above the point where the leaf attaches Within the leaf axil is an axillary bud, a miniature shoot with a dormant apical meristem and several young leaves. ○ it is either a vegetative bud if it will grow into a branch, or a floral bud if it will grow into a flower or group of flowers.  Stem Anatomy Lateral bud are also called axillary buds; develops into a leaf or flower Leaf scar is the remains of the leaf after it has fallen off of the tree; it is just below the lateral bud  Parts of a stem A bud is an embryonic stem which has the potential for further plant growth. It may develop into a leaf, flower or both. Lateral and terminal buds are protected by bud scales – helps the bud survive harsh climate changes; when the bud opens in the spring, the scale falls off leaving a bud scale scar  Lenticels – small spots on the stem that allows a stem to exchange gases (oxygen and carbon dioxide) with the environment. Phyllotaxy “The arrangement of leaves on the stem” Positioning of the leaves is important so that they do not shade each other. The orientation of leaves at one node with respect to those at neighboring nodes is also important. Different types of phyllotaxy are selectively advantageous, depending on leaf size and shape.  If only one leaf is present at each node, the stem has alternate phyllotaxy (the leaves alternate up the stem); two leaves per node is opposite phyllotaxy, and three or more per node is whorled phyllotaxy. Orientation of leaves at one node with respect to those at neighboring nodes In distichous phyllotaxy, the leaves are arranged in only two (di-) rows (-stichies), as in corn and irises. The leaves may be alternate or opposite. In decussate phyllotaxy, the leaves are arranged in four rows; this occurs in only some of the species with opposite leaves. Finally, in spiral phyllotaxy, each leaf is located slightly to the side of the ones immediately above and below it, and the leaves form a spiral up the stem. ○ This is the most common arrangement and may involve alternate, opposite, or whorled leaves INTERNAL STRUCTURE OF ROOTS Epidermis The outermost surface of an herbaceous stem is the epidermis, a layer of parenchyma cells Their outer tangential walls are the interface between the plant and the environment and regulate the interchange of material between the plant and its surroundings. Interior to the epidermis is the cortex  Vascular Tissues Xylem is the tissue of vascular plants that transports water and nutrients from the soil to the stems and leaves. An essential 'supporting' role providing strength to tissues and organs, to maintain plant architecture and resistance to bending. Within xylem are two types of conducting cells: tracheids and vessel elements; both are types of sclerenchyma.. The term "tracheary element" refers to either type of cell.  Vascular Tissues Phloem - Transportation of food and nutrients such as sugar and amino acids from leaves to storage organs and growing parts of plant. This movement of substances is called translocation. 2 types of conducting cells, sieve cells and sieve tube members; the term "sieve element" refers to either one  Characteristics of Herbaceous Stems Have soft, green stems and naked buds Covered with epidermis Grow to a small diameter Lives only for one season (annual) With primary tissues only  Characteristics of Woody Stems Chiefly covered by scales Covered with periderm or bark Grow to a considerable diameter Lives year after year (perennial) With secondary tissues  Secondary Functions of Stems 1. Protection – with thorns (hard, straight, pointed structures; modified branches or stems) E.g. Rose, Bougainvillea, Citrus 2. Photosynthesis – young and green, helps in food production E.g. Kangkong, Squash 3. Unusual support – with tendrils (thin, leafless, spirally curved or coiling structures that are sensitive to contact stimuli) that attaches the plant for support E.g. Ampalaya, Upo  Secondary Functions of Stems 4. Storage – succulent, can store either water or other materials E.g. mucilaginous substances – aloe vera Tannins – Acacia tree Resin – Coniferous trees Latex – Rubber tree Sugar – sugar cane 5. Reproduction – some plant stems can be used for vegetative reproduction such as grafting, marcotting, budding, layering and marching E.g. underground stems like runners (grasses), tubers, rhizomes  OTHER TYPES OF ROOTS AND ROOT MODIFICATIONS Underground stems Rhizomes – a horizontal underground stem which grows near the surface of the soil E.g ginger  Underground stems Tubers – enlarged ends of special underground branches. Each tuber has several eyes. Each eye can develop into a new plant. E.g. potato  Underground stems Bulbs – a short disk – shaped underground stem with many fleshy scales E.g. onion  Underground stems Corm – short, stout , solid and more or less rounded in shape. It is filled with stored food and grows in a vertical direction  Stems for Asexual Reproduction Runner – a slender prostate branch with long or short internodes, creeping on the ground and rooting at the nodes; sub aerial E.g strawberry  Stems for Asexual Reproduction Stolon – a slender lateral branch originating from an underground stem and growing horizontally outwards. It is like a runner, however, it is subterranean. E.g Bermuda grass  Stems for Asexual Reproduction Sucker – like the stolon; it is also a lateral branch developing from the underground part of the stem. However, it grows obliquely upwards and directly gives rise to leafy shoot or a new plant E.g Bamboo  Other specialized stems Tendrils – thin, leafless, spirally curved branch by which climbers attach themselves to other objects E.g Squash  Other specialized stems Thorns – a modified, hard, straight, sharp – pointed stem. It occurs in the axil of a leaf where a branch would normally develop E.g. Lemon, roses, pomelo  Other specialized stems Cladophylls – flattened stems and leaf like in appearance. It has in its center a node bearing very small scale-like leaves with axillary buds. E.g. Asparagus THANK YOU!!! LEAVES  ORIGIN OF THE LEAF Leaf arises from the activity of leaf primordium leaf-like pegs of meristem earliest stage of differentiation Initiation and Development of Leaves Dicot Leaves are produced only through the activity of a shoot apical meristem. At the base, the cells interior to protoderm grow outward and form leaf primordium Leaf primordium- extends upward as a narrow cone and exceeds the shoot apical meristem. Consists of protoderm, ground meristem, provascular tissues ( forms 1˚ xylem and phloem) Leaf primordium grows, increase in thickness, forms midrib and initiate the formation of the lamina Initiation and Development of Leaves Monocot-Similar to dicots Apical meristem adjacent to primordium grow upward giving hood-like shape Tubular portion of leaf primordium continue to surround it as sheathing leaf base Conical leaf primordium gives rise to the lamina Regeneration – meristem can form new lamina after being damaged Meristematic cells remain active mitotically which extends the leaf Physiological function Photosynthesis leaves—the large, flat, green structures involved in photosynthesis Transpiration – the process by which plant loses water to serve the following purposes: a. Continuous uptake of water b. Cooling effects c. Controls degree of saturation of cell with water  Dicot leaf with stipules ( protect Monocot leaf shoot apical meristem while leaf sheath and is young) ligules Economic uses of Leaves Food – The leafy greens are among the most nutritious of foods Herbs – The mint family is a popular herb family Beverages Teas Drug uses Marijuana Economic uses of Leaves Insecticides Rotenone Citronella Waxes Carnauba Aromatic Oils Medical uses Aloe (Mild Topical Anesthetic) Anticoagulant Antibacterial Antifungal ginkgo duhat marigold Part of leaves Lamina/leaf blade, midrib, stipules or ligules-hair-like ○ light-harvesting portion is the leaf blade Petiole or leaf sheath, veins, leaf scar, small leaf-like ○ holds the blade out into the light petiolate-with stalk sessile-without stalk Leaf Classification 1. Nature of the blade 2. Venation pattern 3. Phyllotaxy 4. Leaf margin 5. Leaf apex  1. Nature of the blade a. Simple – with one blade only b. compound- with a blade divided into leaflets or pinnae or pinnule Two types of compound leaves Palmately compound Pinnately compound Leaflets attach to same Leaflets attach individual to point rachis by petiolule Simple Pinnately compound Bipinnately Compound Leaf Tripinnately Compound Leaf a compound leaf having three order of rachises: 1. primary rachis 2. secondary rachis 3. tertiary rachis  Palmately compound leaves – leaflets are attached to the end of the petiole Types of palmately compound leaves: 1. Bifoliate – two leaflets 2. Trifoliate- three leaflets 3. Quadri/tetrafoliate – four leaflets 4. Pentafoliate compound – with 5 or more leaflets Trifoliate Phyllotaxy – arrangement of leaves on the stem  Venation- arrangement of veins on the blade Veins - bundles of vascular; distribute water from stem into leaf and collect sugars produced and carry them to the stem for use or storage Types of parallel venation Parallel to the midrib Palmately parallel Acute angle to the midrib Perpendicular to the midrib Three types of netted venation pattern Pinnately Radiately netted Palmately netted netted Principal veins arise Principal veins arise Veins arise from the from the tip of petiole at from the base or petiole midrib & subdivide the center of the lamina tip Leaf traces- vascular bundles w/c exit the stem and diverge to the petiole Anatomy of leaf A. Epidermal cells with guard cells Guard Are kidney-shaped, chlorophyllous cells epidermal cells Potassium increases turgor pressure Internal structure Epidermis The epidermis is a single layer of cells covering the entire surface of the leaf. coating of waxy cutin Flat epidermal cells, with guard cells, trichomes High number of stomata in lower epidermis tiny pores Trichomes –prevents rapid air movement, prevents water loss from stomata; protection Stomatal crypts – filled w/ trichomes & stomata, at lower surface of leaf, decrease air movement near stomata Mesophyll Most photosynthesis takes place in the mesophyll between the two epidermal layers Parts: Palisade mesophyll Uppermost, main photosynthetic tissue 80% of the leaf’s chloroplasts. 1 layer thick, cells are separated, inc exposure to CO2 Spongy mesophyll loosely arranged parenchyma cells with abundant air spaces Permits CO2 to diffuse rapidly from the stomata to all parts of leaf Vascular tissues Between palisade , spongy mesophyll Dicot: large midrib (midvein) from which lateral veins emerge Minor veins – important in releasing water from xylem and loading sugar into phloem Bundle sheath – fibers arrange as sheath around vascular tissue, present in midrib and lateral veins only makes it difficult for insects to chew into the vascular tissues B. Internal Anatomy of blade epidermis palisade mesophyll spongy epidermis Internal Anatomy of Monocot Leaf Chlorophyllous cells photosynthetic Bundle sheath Kranz Anatomy – Halo or Wreath Anatomy Chlorenchymatous cells surround a photosynthetic bundle sheath.  Bulliform cells are large vacuolated epidermal cells that roll the leaf during hot conditions. Present only in monocot epidermal cells. Kranz anatomy is typical of monocot leaf that undergoes C4 metabolism, plants possess mechanism of CO2 transport, adapt C4 plants in dry environment These plants lack palisade and spongy mesophyll layer but with prominent bundle sheath w/ large chlorophyllous cells Abscission zone detachment area of leaves from the stem Release enzymes w/c weaken their walls Senescence– leaf aging dueto breakdown of chlorophyll, sugars and loss of photosynthetic ability Leaf scar – protective scar tissue across wound after leaf fall Morphology and Anatomy of Other Leaf Types Succulent Leaves thick and fleshy, reduced surface-volume-ratio. With water storage parenchyma; Crassulaceae, katakataka Lithops – pair of translucent Senecio – spherical Dinteranthus – pair of leaves acting as optical fiber, succulent leaves succulent leaves allows light to enter, even leaves are under grd Sclerophyllous Foliage Leaves Thick sclerenchyma Resistant to animals, fungi, freezing temp. and UV, very thick cuticle Lifespan: 2 or more yrs Sclerophylls - leaves Agave Barberry Yucca Spines no blade and needle-shaped, no mesophyll, no vascular tissue Cactus- spines are axillary buds of small leaves Colitis- spines are stipules Stem cortex - photosynthesis Tendrils Sensing contact with other objects When contact with a support is made, not only does the tip curl around it but the direction of the coil reverses sclerenchyma and collenchyma cells then develop in the vicinity of contact. The sclerenchyma cells provide rigid support, while the collenchyma cells impart flexibility. Tendrils Pea plant Squash plant Insect traps Digest insects and obtain nitrogen for their amino acid Passive trap- incapable of movement ex. Pitcher plant Active trap – leaf blade curl, close Nepenthes- pitcher Venus’ flytrap – plant traps insects Sundew- with stalked glands Adventitious buds Produce plantlets Kalanchoe- with plantlets Sansiviera- reproduce by leaf along the leaf margin cutting Colored leaves for attraction Bougainville a Poinsetti a Anthurium- colored spathe Mussaend a Floats Aerenchymatous leaf base for buoyancy, support Water hyacinth – aerenchymatous enlarged leaf base Supporting leaf bases “pseudotrunk” For support Expanded leaf-like petiole or stipule Added photosynthesis Rose leaf Suha leaf Leaves of Conifers Leaves are sclerophylls ○ They have an extremely thick cuticle and the cells of their epidermis and hypodermis have thick walls. Most conifer leaves contain abundant chemicals that make them unpalatable. Conifer leaves are always simple and have only a few forms. Needles, either short or long, occur in all pines, firs, and spruces Bud Scales Bud scales provide this protection by forming a tight layer around the stem tip. Leaves with Kranz Anatomy C4 photosynthesis no palisade and spongy chlorenchyma but have prominent bundle sheaths of chlorophyllous cells with a ring of mesophyll cells important in CO2 transport and adapted to sun-loving plants FLOWERS AND REPRODUCTION Concepts ›Produce offspring that have identical copies of the parental genes. ›Generate new individuals that are genetically different from the parents. ›Stable environment creates adaptability ›Diverse species survive better genetically than homogenous species ›Asexual reproduction – reproduce easily but not good for dispersal. ›Sexual reproduction requires 2 individuals with diverse genes and maybe fit some may be not fit Asexual Reproduction Within the flowering plants, numerous methods of asexual reproduction have evolved One of the most common is fragmentation Sexual Reproduction Sexual reproduction in flowering plants involves the flower itself, which produces the necessary cells and structures. To understand flower structure, one must first understand -The Plant Life Cycle Flower Structure FLOWERS – Reproductive shoot composed of whorls of modified leaves inserted in a modified stem (peduncle)- a stem with leaf like structures FLORAL PARTS Contains four set of parts arranged in whorls on the receptacle the swollen tip of the peduncle Flower Structure Accessory Parts/ Non-essential Sepal (Calyx) o Protects the inner part of the flower, lowermost, outermost, thickest, toughest o Prevents dessication Petal (Corolla) o Most noticeable portion o Different colors with pigment o Perianth – Calyx and corolla; attraction Flower Structure Essential Parts Stamen (Androecium) - Male gametophyte o Pollen containing chamber (microsporangium) o Anther – produces pollen o Filament Carpel (Gymnoecium) – Female reproductive leaf and ovule bearing structure of a flower o Ovary – Produces egg cell; Swollen basal part o Stigma - catches the pollen o Style – Tube like structure Flower Structure Bracts – Floral leaf formed at the base of the flower or lower stalk Modified Stem Receptacle- End of peduncle Pedicel- stem that attaches a single flower to the inflorescence Ovary Position Sexual Reproduction Female Gamete Development Male Gamete Development Fertilization Syngamy of sperm and egg involves both plasmogamy, the fusion of the protoplasms of the gametes, and karyogamy, the fusion of the nuclei. Flower Structure and Cross-pollination Stamen and Style Maturation Times Self-fertilization in flowers that have both stamens and carpels is prevented if anthers and styles mature at different times Exposed pollen lives only briefly, being susceptible to dessication in dry air and to damage to its DNA by ultraviolet light. Agents of Pollination Fertilization & Development of Seed  SEED › Matured Ovule 1. Albuminous – endosperm present e.g. monocot 2. Exalbuminous – no endosperm e.g. dicot seeds Fruit Development True Fruits and Accessory Fruits The term "pericarp" refers to the tissues of the fruit regardless of their origin The terms "pericarp" and "fruit" have been applied to both types of fruit, so now the term true fruit is used to refer to fruits containing only ovarian tissue, and accessory fruit (or false fruit) is used if any non ovarian tissue is present - example: strawberry (receptacle), apple (hypanthium) Fruit Types and Seed Dispersal Fruits are adaptations that result in the protection and distribution of seeds. Matured ovary of the flower after fertilization 1. As to Composition a. Simple Develop from a single ovary. Cherries, peaches, pears, tomato b. Compound i. Multiple Fusion of many ovaries derived from many individual flower (inflorescence) Pinapple ii. Aggregate Fusion of many ovaries derived from a single flower Strawberries, raspberries 2. Nature of Pericarp a. Fleshy – Pericarp is fleshy at maturity i. Berries – All or most of pericarp fleshy ii. Pepo – With hard and thick rind iii. Hesperidium – With a leathery rind containing oil glands in its iv. Drupe – Seeds enclosed within a hard, stony endocarp. Fleshy – Fleshy mesocarp, stony endocarp (eg Mango, peaches, plum) Fibrous drupe – Fibrous mesocarp, stony endocarp (eg. Coconut) v. Pome – Accessory fruit with thick hypanthium; leathery papery endocarp 2. Nature of Pericarp b. Dry – Pericarp layer are dry, apapery and fused together i. Dehiscent - Split open at maturity Legume or Pod - Opens via two suture or seam -Seams – Lines of dehiscence Follicle o One carpel that splits along one seam Capsule o Composed of several fused carpel o Open thru several opening Silique o Two carpel separated by a seed bearing septum 2. Nature of Pericarp ii. Indehiscent – Do not split open at maturity Achene o Consist of a single seed that is attached to the wall of the ovary at only one point The pericarp is also thin and undeveloped so when it tries up the fruit has a seed-like appearance o Fruit and seed are distinct o Fruit wall – papery thin o Eg. Strawberry, sunflower, dandelion Embryo and Seed Development Seed Dispersal THANK YOU!!!