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Transcript
Learning objective • Plant structure of the main parts of a typical flowering plant • Describe the function of roots and stem • Label the parts of a flower on a diagram, and describe the functions of each part • What is the difference between pollination and fertilization? The Shoot System is found ABOVE ground and the Root System is found BELOW or UNDER ground. Plant Body Organization A plant consists of: 1. Root system, which is underground -Anchors the plant, is used to absorb water and minerals, conduction and storage 2. Shoot system, which is above ground -Consists of supporting stems, photosynthetic leaves and reproductive flowers Each has an apex that extends growth Both systems depend on the other. – Lacking chloroplasts and living in the dark, roots would starve without the sugar and other organic nutrients imported from the photosynthetic tissues of the shoot system. – Conversely, the shoot system (and its reproductive tissues, flowers) depends on water and minerals absorbed from the soil by the roots. AXILLARY BUD TERMINAL BUD FLOWER FRUIT NODE SHOOT SYSTEM NODE INTERNODE STEM MAIN ROOT NODE LEAF LATERAL OR SIDE ROOT ROOT SYSTEM The Root Structure of root Types of Root Systems Functions of the Root System Structure of root Roots have several structures, such as root caps and root hairs that stems lack. Root cap • Each root tip is covered by a root cap. • The function of the root cap is to cover and protect the delicate growing tip from injury and damage as the root pushes its way through the soil. Root hairs • Root hairs are tiny projections and outgrowths on the outermost layer of the root epidermis. • The root hairs increase absorption of water and minerals near the root tip. Looks like a tangled mass of roots Examples of plants With this root system are Rice Corn Sugar Cane Fibrous root • A fibrous root system - to many roots of the same size developing from the end of the stem, with smaller lateral roots branching off these roots. • Fibrous root systems, which are located relatively close to the surface of the soil, are adapted to obtain rainwater from a larger area as it drains into the soil. • Monocots most often have fibrous roots. Have a large main central root Have many branching roots Go deep in the soil Examples of plants : Large trees e.g. mango, avocado Shrubs e.g. tomato, peppers • A taproot system - one main root with many smaller lateral roots. Lateral roots often initially occur in regular rows along the length of the main root. • Taproot systems often extend down into the soil to obtain water located deep underground Roots : - anchor plants firmly in the ground - absorb water and minerals from the soil - Storage - some plants, can store starch - of some plants can be used to grow a new plant Question • Name the two organ systems and three basic organs found in all plants. • What are root hairs and what is the function of root hairs? • Briefly explain the fibrous root. • Describe the functions of roots. Summary • The root system is generally underground and obtains water and dissolved nutrient minerals for the plant. • Root also anchor the plant firmly in place. • A tap root system has one main root from which many smaller lateral roots extend. • A fibrous root system has several to many oots of the same size developing from the end of the stem. The shoot system above – ground portion The shoot system consists of stems, leaves, flowers and fruits that contain seeds. And the growth occurs at apex. Some stems grow underground – Bulbs and rhizomes etc. They may be swollen to store food e.g. potatoes. Woody Plant Stem The stems support the leaves and flowers. In the case of a tree, the stems are the trunk and all the branches, including the smallest twigs. External stem structure • Stems all have buds, which are undeveloped embryonic shoots. • A terminal bud (apical) is the embryonic shoot located at the tip of a stem. • Axillary buds, also called lateral buds, are located in the axils of a plant’s leaves. External stem structure • When terminal and Axillary buds grow, they form stems that bear leaves and/or flowers. • The area on a stem where each leaf is attached is called a node, and the region between two successive nodes is an internode. External Stem Structure • Terminal bud = Extends the shoot system during the growing season • Axillary bud = Develops into branches with leaves or may form flowers • Node = Point of attachment of leaf to stem • Internode = Area of stem between two nodes Functions of plant stems • Support • Conduction • Production • Annual –complete their life cycle in a single year or less (grains, legumes) • Biennials - (such as carrot, cabbage) take two years to complete their life cycles before dying. In the first season they produce extra carbohydrates, which they store and use during their second year when they typically form flowers and reproduce. • Perennials – plants that live and reproduce for more than two years. They include trees, shrubs, but herbs can also be perennial. Leaves External Anatomy Leaf Types Function Leaves Tendrils Mayapple Leaves may be round, needle-like, scale like, heart-shaped, fan-shaped, or thin and narrow. They vary in size, colour, texture. EXTERNAL ANATOMY • Leaves possess a blade or lamina, an edge called the margin of the leaf, the veins (vascular bundles), a petiole, and two appendages at the base of the petiole called the stipules. margin Structure The petiole, which joins the leaf to a stem node. Some leaf blades are attached directly to the stem and lack a petiole or stipules. These are termed sessile leaves. Structure • In the absence of petioles in grasses and many other monocots, the base of the leaf forms a sheath that envelops the stem. Some monocots, including palm trees, do have petioles. Structure • The arrangement of veins, differ in monocots and dicots. • Most monocots have parallel major veins that run the length of the blade, while dicot leaves have a multibranched network of major veins. veins Structure: Leaf Types Structure: Leaf Arrangement Function of leaves • Photosynthesis • Transpiration - 99% of water absorbed by plant is lost by transpiration • Exchange of gases – oxygen and carbon dioxide What is the difference between deciduous and evergreen? • Deciduous - they shed all their leaves at the same time and produce new leaves the following rainy season. • Evergreen - shed their leaves over a long time period, so that some leaves are always present. Summary • The shoot system is generally aerial and obtains sunlight and exchanges gases such as carbon dioxide and oxygen – The shoot system consists of a vertical stem that bears leaves (the main organs of photosynthesis) and reproductive structures (in flowering plants, flowers and fruits). – Buds (undeveloped embryonic shoots) develop on stems. Summary • Buds are undeveloped embryonic shoots. A terminal bud is located at the tip of a stem, whereas axillary buds (lateral buds) are located in leaf axils. • The area on a stem where each leaf is attached is called a node, and the region of a stem between two successive nodes is an internode. Summary • Leaves exhibit variation in shape and form. • Leaves typically consist of a broad, flat blade and a stalk-like petiole. Some leaves also possess small, leaf like outgrowths from the base called stipules. • Leaves may be simple or compound • Leaf arrangement on a stem may be alternate, opposite or whorled • Leaves may have parallel or netted (either pinnately netted or palmately netted) venation. Summary • Monocot and dicot leaves can be distinguished based on their external structure. • Monocot leaves have parallel venation, whereas dicot leaves have netted venation. • The main function of stems is support, conduction and production of new living tissues. Basic Flower Structure The Parts of a Flower Most flowers have four parts: • sepals, • petals, • stamens, • Pistil or carpel. Complete flowers • Complete flowers usually have four parts-sepals, petals, stamens and pistilwhich are usually borne on a receptacle. Incomplete flower • Incomplete flowers lack one or more of the four part: sepals, petals, stamens, or pistil. The parts of a flower • Sepals protect the bud until it opens. • Petals attract insects. • Stamens make pollen. • Carpels grow into fruits which contain the seeds. Parts of the Flower • Sepals – Outer covering of the flower bud. – Protects the stamens and pistils when flower is in bud stage. – Collectively known as the calyx. Parts of the Flower • Petals – Brightly colored – Protects stamen & pistils. – Attracts pollinating insects. – Collectively called the corolla. – Collectively sepals (calyx) and petals (corolla) are called the perianth. Parts of the Flower (Stamen) • Male reproductive part – Anther • Produces pollen – Filament • Supports the anther – Collectively or a group of stamens is the androecium. Pistil (female) • Stigma • Style • Carpel (ovary) • Ovules (eggs) Collectively or a group of pistil or carpel is known as Gynoecium Parts of the Flower (Pistil) • Female reproductive part – Ovary • Enlarged portion at base of pistil • Produces ovules which develop into seeds – Stigma • Holds the pollen grains - Style • Connects the stigma with the ovary. • Where pollen tube grows down to female sex cells. • Supports the stigma so that it can be pollinated. Ovules (eggs) • The stamens and pistils are considered the essential parts of the complete flower for sexual reproduction. • The sepal (calyx) and the petals (corolla) are accessory flower parts. • A flower with both stamen and pistil (carpel) are considered as perfect flower. • Imperfect flower has either one but not both. Carpel female parts Stigma Petals Stamen male parts Style Ovary Ovules Sepals Anther Filament Nectaries Collect a cut-out flower, colour it in and put it together. What do the parts do? Sepalsprotect the flower when it is a bud Stamen- anther produces male sex cells (pollen) Petalscolourful to attract the insects Style is where pollen tube grows down to female sex cells. Nectariesgive out sugary liquid to attract insects stigma traps pollen ovary produces female sex cells (ovules) Flowers • Function – Contain the sexual organs for the plant. – Produces fruit, which protects, nourishes and carries seeds. – Attracts insects for pollination. Learn About Plants - Different Parts.flv Quick Test 1. Name the parts of a flower that attract insects. 2. Name the male part of a flower. 3. Which part of the flower contains ovules? 4. Which part of the flower produces pollen? 5. Which part of a flower catches pollen grains? Label the parts of a flower SUMMARY •A flower may contain sepals, petals, stamens, and carpel (pistils). •Sepals cover and protect the flower parts when the flower is a bud. •Petals play an important role in attracting animal pollinators to the flower. •Stamens produce pollen grains. •Each pistil has three sections: a stigma, on which the pollen grains land; a style, through which the pollen tube grows; and an ovary that contains one or more ovules. Pollination and Fertilisation Pollination • Pollination involves the transfer of pollen (male gamete) from the anther to the stigma (outermost female part) • Plants are pollinated by insects or the wind. Pollination Self-pollination • Pollen from the anther is transferred to the stigma in the same flower or a different flower on the same plant Cross Pollination • Pollen from the anther of one plant is transferred to the stigma of a different plant of the same species Learn About Plants - Life Cycle.flv Mode of Pollination 1. Insect-pollinated flowers may have: • Brightly coloured petals- blue or yellow petals. • Strong sweet fragrance • Nectar producing glands • Guidelines to lead insects to Nectar • Stamen are inside • Stigma and pollen are sticky 2. Wind-pollinated flowers may have: • Large stigmas outside the flower • Little or no fragrance • Light non-sticky pollen • Lack showy petals Insect Pollinated Plants Wind Pollinated Plants Wind/Insect Pollination Mode of Pollination (Continued) 3. Bird-pollinated flowers may have: • Long tube shaped flowers • Bright red and yellow flowers • No odour 4. Mammal-pollinated flowers may have: • White flowers • Strong fruity odour • Flowers opening at night 5. Water-pollinated flowers may have: • Pollen which floats on water (this form of pollination is rare) Wind Pollinated Flowers Feature Reason small petals, often brown or dull green no need to attract insects no scent no need to attract insects no nectar no need to attract insects pollen produced in great quantities because most does not reach another flower pollen very light and smooth so it can be blown in the wind anthers loosely attached and dangle out to release pollen into the wind stigma hangs outside the flower to catch the drifting pollen stigma feathery or net like to catch the drifting pollen Insect Pollinated Flowers Feature Reason large, brightly coloured petals to attract insects often sweetly scented to attract insects usually contain nectar to attract insects moderate quantity of pollen less wastage than with wind pollination pollen often sticky or spiky to stick to insects anthers firm and inside flower to brush against insects stigma inside the flower so that the insect brushes against it pollen sticks to it stigma has sticky coating Pollination Summary Structure Wind Pollinated Insect Pollinated Petals dull bright colour Pollen light sticky Stamen dangling inside flower Stigma feathery sticky nectar none makes sugar Fertilisation • Fertilisation involves the fusion of the nucleus of the male gamete (in the pollen) with the nucleus of the female gamete (in the ovules). Fertilisation • Pollen grains germinate on the stigma, growing down the style to reach an ovule. • Fertilised ovules develop into seeds. • The ovary enlarges to form the flesh of the fruit and to protect the ovary. *The ovule forms the seed and the ovary forms the fruit. • A fruit is a ripened ovary Pollination of flowers.flv Seed dispersal Seeds are dispersed in many different ways: • Wind • Explosion • Water • Animals • Birds • Scatter Seed Dispersal- why? Seeds must be carried away (dispersed / scattered) from the parent plant to: • Reduce overcrowding • Reduce competition for: - Water - Light - Nutrients What is a benefit of a seed being dispersed far away from parent plant? • This helps to raise the offsprings chance of survival, at the same time ensuring the parent plants survival. • If the seeds land close to the parent plant competition for resources such as water, sunlight, and nutrients will take place, weakening both the offspring plants as well as the parent plant. How birds and animals help seed dispersal • Some seeds are hidden in the ground as a winter store. • Some fruits have hooks on them and cling to fur or clothes. How birds and animals help seed dispersal • Birds and animals eat the fruits and excrete the seeds away from the parent plant. Seed Dispersal Dispersal method Description Wind Seeds are designed to travel as far as possible. May have extensions which act as parachutes or wings. Fruits may be shaken like a pepper pot. Seeds/ Fruits Learn About Plants - Seed Dispersal.flv Quick Test-A 1. What term is used to describe male and female gametes? 2. What is pollination? 3. Name the two types of pollination. 4. Describe the differences in the pollen between insect and wind pollinated plants. 5. Explain why the stigmas of wind pollinated flowers hang outside the flowers. Quick test-B 1. Why do wind pollinated flowers not produce nectar? 2. How does the male gamete reach the female gamete? 3. What is a fruit? 4. Name three ways in which fruits and seeds are dispersed. 5. Why is it important that fruits and seeds are carried away from the parent plant? Parts Of A Flowering Plant.flv Summary • Pollination is the transfer of pollen grains from anther to stigma. • Flowers pollinated by insects are often yellow or blue and possess a scent. • Bird-pollinated flowers are often yellow, orange or red and do not have a strong scent. • Bat-pollinated flowers often have dusky white petals and possess a scent. • Plants pollinated by wind often have smaller petals or lack petals altogether and do not produce a scent or nectar; wind-pollinated flowers make copious amounts of pollen. Summary • Fertilised ovules develop into seeds. • Seeds are enclosed within fruits, which are mature, ripened ovaries. • Seeds and fruits are adapted for various means of dispersal, including animals, wind, water and explosive dehiscence.