Plant Form and Function BIOL 1306 PDF

9/25/24 Plant Form and Function BIOL 1306: Biology 1 for Majors Jenifer Gifford, Ph.D. [email protected] 0 In this lecture, we will learn: 1. The str...

9/25/24 Plant Form and Function BIOL 1306: Biology 1 for Majors Jenifer Gifford, Ph.D. [email protected] 0 In this lecture, we will learn: 1. The structure and function of angiosperm anatomy (roots, shoots, leaves, and flowers) 2. How seeds and fruits are developed from flowers 3. The structure and function of the three major plant tissues (dermal, ground, and vascular) Overall Importance: Plants, particularly angiosperms, provide the fuel source for life to make energy. Knowing their structure will aid in understanding how they produce and store sugars. 1 1  9/25/24 Study Guide 1. Compare and contrast the structures of monocots vs. dicots 2. Describe the overall structure of a plant (roots, shoots, and leaves) including information regarding the diversity within these structures and the function of each major component 3. Explain the importance of surface area to absorption 4. Describe the structure and function of epidermal, ground, and vascular tissues 5. Describe which structures within a plant are responsible for primary vs. secondary growth 2 Structure Determines Function at all Levels Correlations between structure and function begin at molecular level: Protein shape correlates with their roles as enzymes, structural components of cell, or transporters. Similar correlations between structure and function occur at the cellular level: Example: Cells that secrete digestive enzymes contain a lot of rough ER and Golgi compared to non-secretory cells 3 2  9/25/24 Review: Plant Cells Although eukaryotic cells share many key features, plant cells have several features not found in animal cells: – Plant cells are surrounded by cellulose-rich primary cell wall – Some plant cells have a rigid secondary cell wall – Cytoplasm of adjacent plant cells are connected by plasmodesmata – Chloroplasts are the site of photosynthesis – Large central vacuole: Contain aqueous solution called cell sap and store waste, water, and nutrients 4 Living Things Are Organized and Studied at Different Levels 5 3  9/25/24 Living Things Are Organized and Studied at Different Levels Cells are the smallest unit of life Similar cells group together to form tissues Multiple tissues come together to form organs Organs with related functions are grouped together into organ systems Organ systems work together to support the organism. At each level, the structure determines the function 6 Survival of the Fit Enough Inherited physical structures are adaptations that enhance a plant or animal’s chances of survival and reproduction Structures are often just “good enough” to function and are not necessarily perfect in design Overarching themes of biology: – Structure determines function – Structures/functions often support survival and reproduction 7 4  9/25/24 Introduction to Angiosperms Flowers are the distinguishing characteristics of plants classified as angiosperms; Angiosperms have dominated the earth for 100+ million years; 250,000 species of flowering plants All fruits come from flowers A few hundred domesticated species provides most of our food: beets & carrots; apples, nuts, berries, squashes; peas, peanuts and beans (legumes); wheat, rice and corn (grasses), many herbs etc. 8 Plants Produce Many of Our Staple Foods Vegetables: (Generally) edible components of a plant (leaf, stems, roots etc.) Tuber Vegetables: Specifically edible storage structures on roots or shoots Fruits: Seed bearing food that is produced from flowers Grains: Also fruit, just small, dry, and Legumes: hard fruits Type of fruit that specifically grows in pods Beans: Technically seeds 9 5  9/25/24 Where are we going for the next three units? ATP 10 Two classes of angiosperms: Monocots and Dicots Angiosperms are characterized broadly by the number of leaves that appear upon sprouting. These leaves are called cotyledons Arabidopsis Grass Dicots Monocots 11 6  9/25/24 Two classes of angiosperms: Monocots and dicots differ in: – number of cotyledons (seed leaves) – pattern of leaf venation – arrangement of stem vascular tissue – number of flower parts – root structure 12 PLANT FORM AND FUNCTION: FLOWERS AND SEEDS ARE DESIGNED FOR REPRODUCTIVE SUCCESS 13 7  9/25/24 Plant Lifecycles 14 The Flower is the Organ of Sexual Reproductive Flowers typically contain four types of modified leaves called floral organs. 1. Sepals enclose and protect a flower bud. 2. Petals: colorful and fragrant, advertising the flower to pollinators. 3. Stamens consist of a filament Stigma Carpel Stamen tipped by an anther, which Anther Style contains sacs where pollen Ovary Filament is produced. 4. Carpels: long slender style with a sticky stigma at its tip. Stigma is a landing platform for pollen. Sepal Contains the ovary and one or Petal more ovules, each containing a Ovary developing egg and supporting cells (Ovules) 15 8  9/25/24 Some plants are Monoecious (Male OR Female) 16 Types of Fertilization Self Fertilization Cross Fertilization 17 9  9/25/24 Pollen may be carried by wind, water, and animals. Pollination is the transfer of pollen from anther to stigma. 18 The Development of Pollen/Ovules Results in Reproduction After pollination, the pollen grain germinates on the stigma. – Its tube cell gives rise to the pollen tube, which grows downward into the ovary. – When the pollen tube reaches the base of the ovule, it enters the ovary and discharges two sperm near the embryo sac. Double Fertilization: One sperm fertilizes the egg; the other contributes its nucleus to the large diploid central cell of the embryo sac. This becomes the endosperm. 19 10  9/25/24 The Ovule Develops into a Seed Post-fertilization: ovule begins developing into a seed. Ovule Seed stockpiles proteins, oils, and starches. Embryonic development: zygote divides into two cells. Cell division produces a ball of cells Cotyledons Zygote that becomes the embryo. Endosperm Seed coat A thread of cells anchors the embryo to Two cells the parent plant and pushes the embryo Shoot into the endosperm (food storage). Embryo develops in the ovule to become a mature seed. Near the end of its maturation, the seed Embryo Root loses most of its water and forms a hard, Seed resistant seed coat. 20 The Ovary Develops into a Fruit While the seeds are developing from ovules, hormonal changes triggered by fertilization cause the flower’s ovary to grow, thicken, and mature into a fruit. A fruit is a mature ovary that acts as a vessel, housing and protecting seeds and helping disperse them from the parent plant. Although a fruit typically consists of a mature ovary, it can include other flower parts as well. 21 11  9/25/24 Fruits are Just Plant Ovaries 22 Sprouting Seeds Under the right temperature and moisture levels, seeds germinate The cotlyedons appear at the surface and begin photosynthesis to make sugars to feed the growing tissues. Root and Shoot Systems Develop For photosynthesis to occur efficiently, plants need large amounts of light, CO2, and water Shoot system harvests light and carbon dioxide from atmosphere to produce sugars It also transports water to tissues above ground For synthesis of biomolecules to build the plant, plants need nitrogen, phosphorus, potassium, magnesium, and other nutrients from the soil. Root system anchors plant and takes in water and nutrients from soil 24 12  9/25/24 Plant Tissues Develop from Meristem and Form the Major Plant Organs 25 Early Plant Growth When a plant embryo first develops, the first cells are called meristem cells. Meristem cells are undifferentiated cells are able to divide indefinitely and give rise to many types of differentiated cells 26 13  9/25/24 Early Plant Development Even after development, apical meristems tissue exists at the tips of stems and roots in adult plants. It produces the three types of meristem, which produces three specialized tissues in the plant: 1. Epidermal tissue forms the outer protective covering 2. Ground Tissue fills the interior of the plant 3. Vascular Tissue transports water and nutrients within the plant and also provides support 27 Dermal Tissue Dermal tissue system consists of dermal tissue: – Tissue is also called epidermis – Epidermis is outermost layer of cells – In shoots, primary function is to protect the plant – In roots, primary function is absorbing water and nutrients Epidermis is made up of several different cell types and thus represents a complex tissue 28 14  9/25/24 Dermal Tissue Structures The Cuticle is a waxy layer that forms a continuous sheet on surface of leaves and stems. It minimizes water loss and forms a barrier to protect plant from viruses, bacteria, and spores from parasitic fungi Stomata are pores that allow CO2 to enter and O2 to exit photosynthetically active tissues Root Hairs increase the surface area of the roots in order to increase water uptake Trichomes are hair like structures that can serve as defensive or glandular structures 29 Ground Tissue Ground tissue is responsible for - photosynthesis - carbohydrate storage at the roots - structural support 30 15  9/25/24 Ground Tissue Most photosynthesis and carbohydrate storage takes place in the ground tissue system 1. Parenchyma contains chloroplasts or starch granules 2. Collenchyma provide flexible structural support to actively growing parts of the plant 3. Sclerenchyma contains tough, rigid lignin as well as cellulose Parenchyma Collenchyma 31 Vascular Tissue Vascular tissue system is made up of two complex tissues: xylem and phloem – Xylem conducts water and dissolved nutrients from the root system to the shoot system – Phloem conducts sugars, amino acids, hormones, and other substances from roots to shoots and from shoots to roots Xy HIGH Phlo LOW 32 16  9/25/24 Vascular Tissue: Xylem There are two types of water- conducting cells in Xylem: 1. The xylem of all vascular plants contains tracheids with pits through which water moves 2. In angiosperms, xylem also contains vessel elements with perforations for water transport They form chains with overlapping ends that create tubes within vascular tissue 33 Vascular Tissue: Phloem Phloem contains two types of specialized cells: 1. Sieve-tube elements are long, thin cells with perforated ends called sieve plates 2. Companion cells maintain the cytoplasm and plasma membrane of sieve-tube elements 34 17  9/25/24 Bringing the Tissues Together 35 PLANT FORM AND FUNCTION: ROOTS, SHOOTS, AND LEAVES 36 18  9/25/24 Structure Influences Nutrient Acquisition For photosynthesis to occur efficiently, plants need large amounts of light, CO2, and water Additionally, for synthesis of necessary biomolecules, plants need nitrogen, phosphorus, potassium, magnesium, and other nutrients Two systems can be used to acquire resources: Shoot system harvests light and carbon dioxide from atmosphere to produce sugars Root system anchors plant and takes in water and nutrients from soil 37 Understanding Surface Area and Absorption Structures with Absorption functions are typically folded structures. More Folds= Increased Surface Area = More Absorption Flat Sheet 1X Absorption 1 2 3 4 5 6 1,2 3,4 5,6 3X Absorption Folded Structures 38 19  9/25/24 Nutrient Absorption and Surface Area Both the root and shoot systems function in absorption Roots absorb water soil nutrients and shoots absorb light Plants that are most efficient absorbers have a large surface area compared to its volume 39 Roots, Shoots, and Leaves are Diverse Plant diversity can be analyzed on three levels: 1. Morphological diversity among species 2. Phenotypic plasticity, or changes in structure in individual’s root system in response to the environment. Genetically identical individuals may have very different systems/structures in different environments 3. Modified structures that are specialized for unusual functions 40 20  9/25/24 Root Systems Many root systems have taproot and fibrous roots There are many key functions of the root system: – Roots anchor plant to the soil – Roots absorb ions and water from soil – Roots conduct water and ions to the shoot system – Roots obtain energy from the sugar in the shoot system – Roots store material produced in the shoot system for later use 41 Phenotypic Plasticity of Root Systems Example of Phenotypic Plasticity: Spruce trees tend to have root systems less than a meter deep in waterlogged soil Wet soil lacks oxygen, so their roots are shallow Same tree in drier soil would have deeper root system 42 21  9/25/24 Plant Diversity- Other Types of Root Systems Adventitious roots grow from shoot system: – In ivy, adventitious anchor roots act to anchor the plant – Prop roots of corn brace the plant Pneumatophores—specialized lateral roots that function in gas exchange – Oxygen in atmosphere can diffuse into root system through pneumatophores Storage Roots– Storage for Carbohydrates Biennial plants, such as carrots and beets have storage roots that are a thick taproot that stores carbohydrates during plant’s first two growing seasons 43 Shoot Systems The shoot system contains one or more stems and leaves Stems: Vertical aboveground structures Consist of nodes where leaves are attached, and internodes, or segments between nodes Types of stems: Herbaceous Stems: Exhibit only vertical growth. There is no bark Found in herbs, most standard flowering plants (dandelions, roses, tulips etc). Outermost surface is covered in a cuticle Woody Stems: Exhibits both vertical and outward growth (bark). Found in trees. bushes and shrubs 44 22  9/25/24 Primary Growth Lengthens the Roots and Shoots Apical meristems are found at the tips of roots and in the buds of shoots and results in primary growth, which allows roots to push downward through the soil and shoots to grow upward, increasing exposure to light and CO2 The apical meristems of root tips are covered by a root cap. Root growth occurs behind the root cap in three zones. 1. Zone of cell division, which includes the apical meristem and cells derived from it. 2. Zone of elongation, where cells lengthen by as much as 10 times. 3. Zone of differentiation, where cells differentiate into dermal, vascular, and ground tissues, including the formation of primary xylem and primary phloem. 45 Removing the Terminal Bud Causes Branching and 46 23  9/25/24 Secondary Growth Thickens the Diameter Secondary growth is an increase in thickness of stems and roots and occurs at Lateral Meristems/Cambium Cambium differs in location from an apical meristem. It forms a cylinder that runs the length of the root, trunk, or branch. Cambium cells divide to increase the width of the plant There are two types of cambia in plants: 1. Vascular cambium is located between secondary xylem and secondary phloem 2. Cork cambium is located near the outer perimeter of the root, trunk, or branch 47 Secondary Growth Thickens the Diameter Vascular cambium produces: 1. Secondary xylem which produces wood toward the interior of the stem. 2. Secondary phloem produces the inner bark toward the exterior of the stem. Cork cambium produces cells in one direction, the outer bark, which is composed of cork cells. 48 24  9/25/24 Secondary Growth Thickens the Diameter Newest Grow is at the Tip of New Branches 49 You hammer a nail into a tree trunk 2 meters above the ground. The tree is currently 5 meters tall and grows taller at a rate of 1 meter per year. How far above ground level will the nail be in 10 years? A. 2 meters B. 5 meters C. 15 meters D. 20 meters 50 25  9/25/24 A tree will die if the bark is stripped off around the entire circumference of the tree. Why is this so? A. Water-conducting cells in xylem are removed, and the tree can no longer conduct water and minerals up the trunk to the leaves. B. Phloem cells are removed, sugars can no longer be transported from the leaves to the roots, and the roots will die. C. The apical meristems are removed, preventing any further increase in height. D. Oxygen is lethal to the inner wood of tree trunks. 51 Phenotypic Plasticity of Shoot Systems Shoot systems range in size Size and shape of a plant’s shoot system can vary based on variation in growing conditions Variation in size and shape of shoot system of various species minimizes competition for light: – Lush environments and competition for light favors taller shoot systems – Dry, windblown habitats favor short stems that are more anchored to the soil 52 26  9/25/24 Modified Shoot Systems 53 Leaf Structural Diversity Vast majority of photosynthesis occurs in leaves: – Leaf’s relatively large surface area available for absorbing photons and supporting photosynthesis Simple leaf has two main structures: Expanded blade and a Stalk called petiole Arrangement of leaves on stem may vary 54 27  9/25/24 Phenotypic Plasticity of Leaves Although leaves do not grow continuously, they do exhibit phenotypic plasticity Oak tree leaves vary depending on amount of sunlight they are exposed to: Shade leaves: Relatively large and broad, providing high surface area to maximize photon absorption Sun leaves: Have relatively small surface area, reducing water loss in areas of body where light is abundant 55 Modified Leaves Onion bulbs store nutrients The leaves of succulents store water Tendrils enable vines to climb The bright red leaves of poinsettias attract pollinators The tubelike leaves of the pitcher plant trap insects Cactus spines protect the stem 56 28  9/25/24 Modified Leaves sometimes look like flowers 57 58 29