Plant Tissues and Organs - PDF

Protoderm o Green outline THE PLANT TISSUES AND VEGETATIVE ORGANS o Becomes the epidermis Each plant may have unique characteristics that Procambium...

Protoderm o Green outline THE PLANT TISSUES AND VEGETATIVE ORGANS o Becomes the epidermis Each plant may have unique characteristics that Procambium differentiate them from other plants (shape, size, texture, o Where the xylem and phloem are found color, life cycle, season of growth) Ground meristem Despite differences, plants share common structures o Where parenchyma, collenchyma, and o Plant body - stems, roots, leaves sclerenchyma tissue or cells are found o Plants need the same nutrients for growth - nitrogen, potassium, phosphorus, water, sugar BASIC PLANT MORPHOLOGY Two systems: MERISTEM o Shoot system ➔ Consists of the stem, leaf, flower, fruit, buds Description: Plants’ growing points o Root system o Where cell division takes place ➔ Consists of the root only Types: Six organs: o Root 1. Primary/Apical More on the increase in length o Stem Types: o Leaf ○ Shoot apex o Flower ○ Root apex o Fruit o Seed 2. Secondary/Lateral THREE BASIC TISSUE More on the increase in diameter/ TYPES: thickness/girth Types: Dermal - often found ○ Vascular cambium in the skin ○ Cork cambium Ground - composed of several cells o Parenchyma o Collenchyma o Sclerenchyma Vascular SIMPLE TISSUES Description: consists of one cell type o Both dermal tissue and ground tissue are classified as simple tissue. DO | BLOCK 05191D 1  DRINK WATER, STAY HYDRATED [ CHANGE IF WANT ] Trichomes TYPES OF PLANT CELLS AND TISSUES o Function for protection against herbivores Fundamental cell/tissue types: o Parenchyma cell/tissue ➔ Functions mainly for photosynthesis ➔ Can multiply ➔ Live cells o Collenchyma cell/tissue o Sclerenchyma cell/tissue ➔ Dead cells ➔ Do not multiply General plant tissue types based on location and function: o Dermal/epidermis ➔ Parenchyma cell/tissue o Ground/cortex and pith ➔ Parenchyma, collenchyma, and/or sclerenchyma cell/tissue o Vascular/xylem and phloem ➔ Parenchyma and sclerenchyma cell/tissue EPIDERMIS Description: Contains several types of cells Function: o Serve as opening for the exchange of gases Stomate/stomata o Mainly located in the leaves o Serve as a natural opening for the exchange of gases PARENCHYMA Description: alive at maturity o Have thin and flexible primary cell walls o Lack secondary walls Functions: o Performs the most metabolic functions ➔ Photosynthesis ➔ Storage ➔ Secretion (glands, trichomes) o Retain the ability to divide and differentiate ➔ Mitosis - wound-healing and cloning o Protection ➔ Epidermis Root hairs o Are unicellular o Helps in the absorption of water and minerals needed by plants DO | BLOCK 05191D 2  DRINK WATER, STAY HYDRATED [ CHANGE IF WANT ] CHLORENCHYMA STELLATE PARENCHYMA Description: mainly for photosynthesis Description: a form of aerenchyma o Found in the leaves o Found in aquatic plants STORAGE PARENCHYMA Description: mostly found in the roots COLLENCHYMA Collenchyma cells o Are groups in strands and help support young parts of the plant shoot o There cells provide flexible support without restraining growth o Have thicker and uneven cell walls AERENCHYMA Function: for aeration SCLERENCHYMA Sclerenchyma cells o Are rigid because of the thick secondary wells strengthened with lignin o Are dead at functional maturity Lignin o an indigestible strengthening polymer Two types: o Sclereids - are short, irregular in shape, and have thick lignified secondary walls o Fibers - are long, slender, and arranged in threads DO | BLOCK 05191D 3  DRINK WATER, STAY HYDRATED [ CHANGE IF WANT ] Phloem o Mostly to conduct sugars, amino acids, etc. (e.g. leaves to roots or flowers) o Movement is downward COMPLEX TISSUES 1. Xylem A vascular tissue Water conducting tissue Composed of parenchyma, fibers, vessels, and/or tracheids, and ray cells 2. Phloem A vascular tissue Food conducting tissue Composed of: ○ Sieve-tube members ➔ No nucleus at maturity ➔ Cytoplasm present ○ Companion cells ○ Fibers COMPARISON BETWEEN ○ Parenchyma VESSEL MEMBER AND TRACHEID ○ Ray cells 3. Periderm Protective covering Composed of cork and parenchyma 4. Secretory structures Responsible for making latex, resins, nectar, and other substances Produces and stores in channels inside the plant body VASCULAR TISSUE Xylem o Mostly conduct water and nutrients (e.g. roots to shoots) o Movement is upward SUMMARY OF PRIMARY AND SECONDARY GROWTH IN A WOODY STEM DO | BLOCK 05191D 4  DRINK WATER, STAY HYDRATED [ CHANGE IF WANT ] THE ROOTS STRUCTURES UNIQUE TO ROOTS Description: are generally underground structures o Anchor the plant 1. Root cap o Are generally non-green due to the lack of Each root tip has a root cap chlorophyll It is a protective loose layer of cells o Transport water and nutrients from the soil Covers the delicate root apical meristem o Are positively geotropic (downward growth of plant Detects gravity so the root grows download structures) (positively gravitropic) o Are positively hydrotropic (grow towards moisture) Secretes a mucilaginous substance that o Are negatively phototropic (grow away from light) moistens ground and facilitates root Embryonic root or radicle penetration and nutrient absorption 2. Root hairs Each hair is a unicellular extension of the root epidermis An extension of an epidermal cell of a root that increases the absorptive capacity of the root Short-lived ○ Are functional for a few days or weeks only Increase surface area of the root in contact with moist soil, increasing the root’s absorptive capacity WORLD’S BIGGEST SEED WITH EMBRYONIC ROOT OR RADICLE The Royal Botanic Garden in Edinburgh germinated a bowling-ball-like coco de mer (Lodoicea maldivica) palm. The seed weighs 35lb (16kg) and can produce a tree that will live up to 300 years Scottish botanists put it in a dark case, and now a root has developed. o It will produce one leaf a year for the next few years. o The tree will begin to flower in 20-30 years and produce its own seeds after another five to seven years (10-09-03) DO | BLOCK 05191D 5  DRINK WATER, STAY HYDRATED [ CHANGE IF WANT ] ROOT ANATOMY Epidermis o Outer protective covering Ground tissues o Consists of parenchyma cells and usually stores starch o Found in the cortex and pith (in certain roots) Vascular tissues o Complex tissues for conduction of substances o Xylem conducts water and dissolved minerals o Phloem conducts dissolved sugar Endodermis CROSS SECTION OF A PRIMARY ROOT o Innermost layer of the cortex of the root that prevents water and dissolved materials from Similarities (between dicot and monocot): entering the xylem by passing between cells o Vascular bundle (stele) - contains xylem and Casparian strip phloem o A band of waterproof material around the radial and o Cortex transverse cells of the endodermis o Epidermis o Ensures that water and minerals enter the xylem only by passing through the endodermal cells Pericycle o A layer of cells just inside the endodermis of the root o Gives rise to lateral roots COMPARING MONOCOT AND EUDICOT ROOTS 1. Monocot roots often have a pith in the center of the root In herbaceous eudicot roots, the xylem and phloem form a solid mass in the center of the root 2. Monocot roots lack a vascular cambium Because they do not undergo secondary growth 3. Dicots give rise to corks and cambium 4. Dicots have a limited number of xylem and phloem DO | BLOCK 05191D 6  DRINK WATER, STAY HYDRATED [ CHANGE IF WANT ] 2. Fibrous root system A root system consisting of several adventitious roots of approximately equal size that arise from the base of the stem MAIN FUNCTION OF ROOTS Anchorage Absorption WATER MOVEMENT Conduction Storage In a primary eudicot root, water moves from soil into center of the root: o Root hair → epidermis → cortex (symplast or apoplast pathway) → endodermis → pericycle → MODIFIED ROOTS xylem Water is transported upward through the root xylem into May function in/as: the stem xylem and the rest of the plant Food storage Propagative roots Symplast o A continuum consisting of the cytoplasm of many plant cells, connected from one cell to the next by Pneumatophores Aerial roots plasmodesmata Apoplast Photosynthetic roots of Buttress roots o A continuum consisting of the interconnected, some orchids porous plant cell walls, along which water moves freely Parasitic roots Symbiotic roots - mycorrhizae or “fungus roots” and legumes (e.g. pea, beans, peanuts), and bacterium form root nodules STORAGE ROOTS TYPES OF ROOT SYSTEMS 1. Taproot system A root system consisting of one prominent main root with smaller lateral roots branching from it DO | BLOCK 05191D 7  DRINK WATER, STAY HYDRATED [ CHANGE IF WANT ] PNEUMATOPHORES SPECIALIZED ROOTS (CONTRACTILE ROOTS) Description: a specialized aerial root produced by certain trees living in swampy habitats o May facilitate gas exchange between the atmosphere and submerged roots PHOTOSYNTHETIC ROOTS BUTTRESS ROOTS Description: Swollen bases or braces that hold trees upright o Aid in extensive distribution of shallow roots o Found in some tropical rainforest trees SYMBIOTIC ROOTS Mycorrhiza o a mutually beneficial association or symbiotic relationship forms between a fungus and a root that helps the plant absorb essential minerals from the soil o Also known as “fungus roots” o Fungus ➔ Provides protection against some types of PROP ROOTS pathogens ➔ Increase the surface area for the absorption Description: An adventitious root that arises from the of essential nutrients (e.g. phosphorous) stem and provides additional support for the plant from the soil o Plant ➔ Provides food for the fungus in the form of sugar and amino acids DO | BLOCK 05191D 8  DRINK WATER, STAY HYDRATED [ CHANGE IF WANT ] Nodule o a small swelling on the root of a leguminous plant in ECONOMIC IMPORTANCE OF ROOTS which beneficial nitrogen-fixing bacteria (Rhizobium) live 1. Rootcrops as source of starch Root nodule Predominantly taproots o Legumes (e.g. pea, beans, peanuts) ○ Carrots, beets, sugar beets, o Mutualism between a plant and bacterium parsnips, turnips, radishes ➔ Bacteria fix atmospheric nitrogen to form that Some fibrous roots the plant can utilize ○ Sweet potatoes, cassava ➔ Plant provides food and shelter to bacteria 2. Some roots are used as flavorings Example: root beer flavoring (dried PARASITIC ROOTS greenbrier roots) 3. Medicine THE STEM Description: serves as an attachment for the organs Functions: transportation of water and minels 6 elements: o Nodes o Internodes o Terminal or apical bud o Lateral or axillary buddy o Petiole o Pedicel 2 organs: o Leaves o Flowers WOODY TWIG PROPAGATIVE ROOTS WITH ADVENTITIOUS BUDS/STEMS By counting the number of bundle scar, we are able to determine the age of a twig DO | BLOCK 05191D 9  DRINK WATER, STAY HYDRATED [ CHANGE IF WANT ] SHOOT APEX MAIN FUNCTIONS OF STEMS 1. Support Description: consists of three primary meristems Leaves and reproductive structures o Protoderm - gives rise to the epidermis o Precambium - gives rise to vascular tissues 2. Conduct o Ground meristem - gives rise to ground tissues Water, dissolved materials, carbohydrates 3. Produce new living tissues STEM ANATOMY At apical meristems At lateral meristems (secondary growth) SECONDARY GROWTH Description: Takes place in woody dicots and gymnosperms How extensive could secondary growth go? o Sequoia sempervirens ➔ world's tallest tree stands at 112 m, that is 19 m taller than the Statue of Liberty o Chestnut tree (Castanea sp.) from Sicily ➔ world's fattest tree at 58 m circumference o Pinus longaeva (bristlecone pine) from Californi Pith ➔ world's oldest tree at >5000 years old o Found in monocots o Albizia falcata from Malaysia o Spongy tissue in the center of the stem ➔ world's fastest growing tree at 10m tall in 13 o Functions for storage of molecules months THE WORLD’S MOST MASSIVE LIVING THING Giant sequoia (Sequoiadendron giganteum) o has the undisputed record for the world's most massive living thing. General Sherman o The largest tree o is 272 feet (83 m) tall with a massive trunk 35 feet (11 m) in diameter and 109 feet (33 m) in circumference at the base. o It has been estimated to contain over 600,000 board feet of timber, enough to build 120 average-sized houses. o The trunk of General Sherman alone weighs nearly 1400 tons. o By way of comparison, this is roughly equivalent to 15 adult blue whales, 10 diesel-electric train locomotives, or 25 average-sized military battle tanks. DO | BLOCK 05191D 10  DRINK WATER, STAY HYDRATED [ CHANGE IF WANT ] MASSIVE FLOWERING THINGS DETERMINING THE AGE OF THE TREE Can be done by measuring the girth of the trunk South African baobab tree (Adansonia "Wood" digitata) o secondary xylem, or everything on the interior side The enormous trunk may exceed 100 of the vascular cambium feet (30 m) in circumference and store "Bark" 25,000 gallons of water weighing 100 o everything exterior of the vascular cambium, tons. including the secondary phloem and the periderm (cork cambium + cork) Also remember: o Secondary growth happens in roots too. THE ONSET OF SECONDARY GROWTH Vascular cambium and cork cambium increases the thickness of the stem during secondary growth. Primary growth o occurs with action of the apical meristem Periderm Secondary growth o Composed of the cork cambium and cork o occurs with action of the cambium o Functions mainly for protection, water preservation, and insulation Bark o Composed of the periderm, secondary phloem, and vascular cambium SECONDARY GROWTH OF A STEM Occurs in lateral meristems Sapwood o Cork o Light colored portion of the tree trunk cambium o Where water passes from the roots to the leaves o Vascular o Outermost portion of the woody stem cambium Heartwood o Center of the trunk o Dead inner wood o Darker in color o Starts from sapwood o Trees may still live even if the heartwood and a little sapwood is removed ➔ However, the consequence is the tree becoming less resistant to harsh conditions DO | BLOCK 05191D 11  DRINK WATER, STAY HYDRATED [ CHANGE IF WANT ] MODIFIED STEMS ABOVEGROUND STEMS 1. Thorn 2. Tendril Thread-like appendage of plants Used by plants e.g. grapes to cling unto wires or bamboo LENTICELS Description: porous tissues that are the usual components of periderm of stems and roots o Except in stems with regular periderm formation and shed their outer bark annually Are found in: o Surfaces of leaves in certain taxa 3. Cladophyll o Surfaces of fruits, e.g. apples, pears, and plums o Potato tubers and sweet potato roots Parts of a lenticel: Is photosynthetic 4. Stolon or runner Lenticel shapes 5. Sucker 6. Tiller 7. Offset DO | BLOCK 05191D 12  DRINK WATER, STAY HYDRATED [ CHANGE IF WANT ] UNDERGROUND STEMS ECONOMIC IMPORTANCE OF STEM Food 1. Tuber o Stem of celery, bamboo shoot, sugar cane The thickened end of a Medicine rhizome that is fleshy and o Stem of ginger, herbaceous, and traditional plants enlarged for food storage Paper Ex. white potato o Stem of bamboo, etc. Resin Fuel Lumber THE LEAVES MONOCOT AND DICOT LEAVES Difference between monocot and dicot: 2. Bulb o Their shape is different — long and slender shape A rounded, fleshy for monocots, while dicots are broader and rounded underground bud that o Veins - monocot’s veins are parallel in form while consists of a short stem the dicot is more complex with fleshy leaves Ex. onion 3. Rhizome A horizontal underground stem that often serves as a storage organ and a means of asexual reproduction Ex. iris MONOCOT LEAF 4. Corn A short, thickened underground stem specialized for food storage and asexual reproduction Ex. crocus DO | BLOCK 05191D 13  DRINK WATER, STAY HYDRATED [ CHANGE IF WANT ] LEAF MORPHOLOGY LEAF SHAPE Can be characterized based on the type of leaves in Shape or outline of leaves: terms of: a. Venation b. Phyllotaxy c. Leaf shape d. Base e. Margin f. Apex Simple leaves o Single blade per petiole Other common shapes: Compound leaves o Divided into smaller leaflets but originate from a single axillary bud o Pinnately compound - have leaflets in pairs along VENATION an extension of the petiole Description: arrangement of veins o Palmately compound - all the leaflets attached at Parallel venation the same point at the end of the petiole o Veins running parallel with one another o E.g. monocots Netted venation o Pinnately veined leaves - one primary vein (midvein) which is included within an enlarged midrib o Palmately veined leaves - several primary veins fan out from the base of the blade DO | BLOCK 05191D 14  DRINK WATER, STAY HYDRATED [ CHANGE IF WANT ] Other leaf venations: Normal Amplexicaul o Base is attached to the stem Perfoliate o Base encloses the stem Connate o Two leaves are joined together and encloses the stem at the middle Peltrate o Similar to the umbrella Sheathing o Grass, bamboo, rice, corn PHYLLOTAXY Description: arrangement of leaves on the stem Opposite o Oppositely arranged Whorled o Spiraling Alternate o Alternately arranged Rosette o Similar to whorled, but in a circular arrangement APEX Description: tip of the leaf LEAF ATTACHMENT TO STEM DO | BLOCK 05191D 15  DRINK WATER, STAY HYDRATED [ CHANGE IF WANT ] LEAF BASE Description: lowermost part of the leaf MONOCOT LEAVES LEAF MARGINS Description: mesophyll layer of the monocot is not Description: outside edge of the leaf well-differentiated into palisade and spongy layers (isobilateral) Bulliform cells o Large, thin-walled cells located at the upper epidermis; helps reduce water loss LEAF ANATOMY Epidermal tissue o Skin or outermost layer of the leaf Mesophyll o Palisade parenchyma - where photosynthetic activity occurs due to the abundance of chloroplasts o Spongy parenchyma - contain little to no chloroplasts Xylem and Phloem o Where water and other minerals are transported Stomata o Composed of two guard cells LEAF EPIDERMIS Description: cell layer that covers the outer surface of the leaves 3 basic kinds of epidermal cells o Ordinary epidermal cells - may show a variety of shapes depending on the species and usually covered by cuticle o Trichomes or hair cells - prevents water loss and acts as protection against herbivores o Guard cells STOMATA Description: pore or opening mostly in the lower epidermis o It is the only passageway of atmospheric gases into and out of the leaves DO | BLOCK 05191D 16  DRINK WATER, STAY HYDRATED [ CHANGE IF WANT ] o Opening and closing is based on the movement of o Desert plants (xerophytes) guard cells ➔ Thick and reduced leaves o Average of 100 per sq. mm ➔ Stomata opens only at night time ➔ Thick waxy layer o Conifers ➔ With waxy needle leaves ➔ Evergreen ➔ Thick, waxy cuticle ➔ Sunken stomata SPECIALIZED OR MODIFIED LEAVES 1. Cotyledons or “seed leaves” Leaves are produced by a germinating seed often contain a store of food (obtained from Factors affecting stomatal movement: the endosperm) to help the seedling become established. 1. Light generally causes it to open and darkness closes it Phototropins expressed in guard cells act as major blue light receptors for stomatal opening Phototropins are plant-specific blue-light receptor proteins for phototropism, chloroplast movement, leaf expansion, and stomatal opening. 2. Low Water/Moisture availability causes it to close to 2. Colored bracts prevent further water loss Petal-like leaves to attract pollinators Brightly-colored to attract pollinators 3. Temperature changes- hi her temperature will cause stomata to close to prevent water loss 4. CO2 concentration - low conc causes it to open. 3. Insect-trapping leaves All these plants live under nutrient-poor conditions and digest insect bodies to obtain nitrogen and other essential nutrients. Pitcher plants, sundews venus flytraps, and bladderworts have modified leaves for capturing insects 4. Tendrils Depending on the environment, some species develop blade of leaves or leaflets are reduced in their own adaptations size, allowing the plant to cling to other objects (e.g., sweet pea and garden peas) DO | BLOCK 05191D 17  DRINK WATER, STAY HYDRATED [ CHANGE IF WANT ] 5. Spines 11. Flower pot leaves In cacti and euphorbs, leaves are often To catch water and debris for nutrient reduced such that they serve as spine to collection discourage herbivory and reduce water loss; Dynaria sp. stems serve as the primary organ of photosynthesis. PLANT ADAPTATIONS TO HABITATS 6. Storage leaves Succulent leaves retain water in large vacuoles MESOPHYTES Description: Plants adapted to a habitat with adequate 7. Absorptive leaf water Hydrilla sp. HALOPHYTES Description: Plants adapted to a salty habitat or saline environments o 80% of the earth is covered by saline water o Very few plants are able to tolerate saline conditions without serious damage o c.f. Glycophytes Most halophytes prefer saline conditions but can survive in freshwater environments Most halophytes are restricted to saline environments Reponses to increased salts: o Succulence - plant organs are thickened due to 8. Reproductive leaves increased cellular water content Mother of Thousands (Kalanchoe o Increased growth - Reduces cellular solute daigremontiana) concentrations HYDROPHYTES Description: Plants adapted to a freshwater habitat o Plants which live wholly or partly submerged in freshwater Adaptations of hydrophytes: o Have lots of air spaces in their tissues to help them float in water o Little/no mechanical for buoyancy and resistance against tissue less water current. o Absence of stomata for submerged plants or stomata on the surface only for floating plants. o Thin cuticle 9. Stipules Photosynthetic leafy outgrowth XEROPHYTES Description: Plants adapted to a dry habitat o Possess some or all of these adaptations to prevent excessive water loss 10. Expanded petiole Adaptations of xerophytes For photosynthesis o Stomata sunken in pits creates local Pomelo, oranges, etc. humidity/decreases exposure to air currents DO | BLOCK 05191D 18  DRINK WATER, STAY HYDRATED [ CHANGE IF WANT ] o Presence of hairs creates local humidity next to leaf/decreases exposure to air currents by reducing flow around stomata o Thick waxy cuticle makes more waterproof impermeable to water LEAF ABSCISSION In temperate climates, most woody plants with broad leaves shed leaves in fall o Helps them survive low temperatures of winter Involves physiological and anatomical changes ECONOMIC IMPORTANCE OF LEAVES 1. Food, Spices, Drinks Cabbage, lettuce, spinach, celery, parsley, Agave 2. Dyes red dye from Lawsonia inermis (henna) 3. Fibers abaca, pineapple, jute 4. Fuel yareta (Azorella yareta) with flammable resin 5. Drugs digitalis and digitoxin from foxglove (Digitalis purpurea) REFERENCES Notes from the discussion by Sir Peter Magdaraog De La Salle University Powerpoint Presentation DO | BLOCK 05191D 19