Chapter 34 Lecture Presentation PDF

Chapter 34 Roadmap Chapter 34 Learning Objectives At the completion of this section, you should be able to ….. Plant Tissues and Organs: Contrast the functions of plant roots, stems, xylem, phloem, leaves, reproductive structures, and stomata. Adaptations to Environmental Stress: Predict...

Chapter 34 Roadmap Chapter 34 Learning Objectives At the completion of this section, you should be able to ….. Plant Tissues and Organs: Contrast the functions of plant roots, stems, xylem, phloem, leaves, reproductive structures, and stomata. Adaptations to Environmental Stress: Predict the impact of changes in plant characteristics or environmental conditions on photosynthetic rates, water loss, growth, and plant survival. Plant Development: Analyze the processes enabling shoots and roots to increase in length and width. Most Plants Can Grow Throughout their Lives - Indeterminate Growth One of the largest Welwitschia plants in the Namib desert. Some are 2,000 years old. One of the bristlecone pines in the high mountains of California. Some are 5,000 years old. Most Plants Can Grow Throughout their Lives - Indeterminate Growth Structure of a plant's body is dynamic. Trimming a plant often results in regrowth, exhibiting different yet somewhat predictable forms. Examples include bonsai and landscaping Cut 34.1 Plant Form: Themes with Many Variations Photosynthesis Requirements: – Efficient photosynthesis necessitates abundant light, CO2, and water Nutrient Needs for Synthesis: – For synthesizing carbohydrates, proteins, nucleic acids, and lipids – Plants require nutrients such as nitrogen, phosphorus, potassium, magnesium, and others - primarily as ions dissolved in soil water Typical Root and Shoot Systems Acquire and Transport Resources ▪ Tissue ▪ Cells working together with a common function ▪ Organ ▪ Tissues working together with a common function ▪ 3 basic organs: Roots Stems Leaves Root System (1 of 3) Root System: – Root systems can have taproots and lateral roots. Key Functions: ▪ Anchor Plant: Secures the plant in the soil. ▪ Absorption: Takes up ions and water from the soil. ▪ Conduction: Transports water and ions to the shoot system. ▪ Energy Source: Derives energy from sugars in the shoot system. ▪ Storage: Stores materials produced in the shoot system. Prairie grasses show diversity among species, minimizing competition for water and resources Phenotypic Plasticity in Root Systems Morphological diversity in roots also occurs within and among species Roots show phenotypic plasticity: – Form is changeable depending on environment Lateral root Lateral root proliferation of proliferation of barley in barley in response to a response to a nutrients patch. uniform nutrients patch. Form and Function of Modified Roots Adventitious roots grow from shoot system: Modified Root Example Anchor roots The photograph shows a thick, tubular stem covered with a fringe of small, fibrous extensions that adhere to a rock behind the tube. These adventitious roots anchor stems to walls and to other plants. These adventitious roots anchor stems to walls and to other plants The photograph shows the bottom of a woody Prop roots stem from which many smaller, tubular extensions reach from the stem and into the soil. These adventitious roots stabilize the stem. These adventitious roots stabilize the stem Form and Function of Modified Roots Modified Root Example Pneumatophores The photograph shows a cluster of spike like structures extending from the soil. Pneumatophores allow gas exchange between Specialized lateral roots roots and atmosphere. Pneumatophores allow gas exchange between roots and atmosphere Storage roots The photograph of a stack of sugar beets that have been plucked from the soil. These have Thick taproot that stores large, bulbous pale roots topped by green carbohydrates during plant’s first two foliage. Sugar beets store carbohydrates and growing seasons other nutrients in their taproot for future use. Sugar beets store carbohydrates and other nutrients in their taproot for future use Typical Root and Shoot Systems Acquire and Transport Resources ▪ Tissue ▪ Cells working together with a common function ▪ Organ ▪ Tissues working together with a common function ▪ 3 basic organs Roots Stems Leaves Phenotypic Plasticity in Shoot Systems Size and shape of a plant's shoot system can vary based on growing conditions such as temperature, wind exposure, water availability, nutrient levels, and light. Genetically identical plants: Morphological Diversity in Leaves (1 of 2) Vast majority of photosynthesis occurs in leaves: Morphological Diversity in Leaves (2 of 2) Leaf Arrangement: Leaves may: Alternate on either side of the stem. Pair opposite each other on the stem. Be arranged in a whorl. Form a compact basal arrangement with extremely short internodes, resulting in a rosette growth form. Phenotypic Plasticity in Leaves While leaves don't grow continuously, they do show phenotypic plasticity—variations in phenotype due to the environment. Example - Oak Leaves: Sun Leaves: Small surface area, reducing water loss in abundant light. Shade Leaves: Large and broad, maximizing photon absorption with a high surface area. 34.2 Plant Cells and Tissue Systems Plant Tissue Systems Plant tissues grouped into tissue systems, based on their structural features and location within plant: – Simple tissues consist of a single cell type; complex tissues contain several types of cells Three tissue systems are found in plants: 1. Dermal tissue system 2. Ground tissue system 3. Vascular tissue system Dermal Tissue System Epidermis: outer tissue layer; various cells Stomata: regulate gas exchange and water loss Dermal Tissue System Trichomes: hair-like appendages composed of specialized epidermal cells, serving various functions. Ground Tissue System Most photosynthesis and carbohydrate storage takes place in the ground tissue system Ground tissue: – Complex tissue made up of three distinct tissues: 1. Parenchyma 2. Collenchyma 3. Sclerenchyma Parenchyma Cells May Perform Photosynthetic or Storage Functions Parenchyma: − Relatively thin primary cell walls − Most abundant and versatile plant cells Collenchyma: Simple Tissue with Cells That Function Primarily in Shoot Support Collenchyma: Characteristics: – Unevenly thickened primary cell walls. Function: – Provides flexible structural support to actively growing parts of the plant. Location: – Often found just under the epidermis of stems, especially outside vascular bundles. Sclerenchyma: Simple Tissue with Two Types of Specialized Support Cells Sclerenchyma Tissue: Cell Characteristics: – Thin primary cell wall and thick, rigid secondary cell wall. – Secondary cell wall contains tough lignin and cellulose. Cell Types: – Fibers: Elongated cells. – Sclereids: Short cells with variable shapes, functioning in protection. Sclerenchyma Cells Support Mature Tissues Vascular Tissue System Phloem: conducts Xylem: conducts sugars, amino acids, water and dissolved hormones, and other nutrients substances Shoots Shoots Roots Roots  Xylem Structure Xylem Composition: – Complex tissue with water-conducting cells, parenchyma cells, and fibers. Water-Conducting Cells: – Two types: ▪ All vascular plants have tracheids with pits facilitating water movement. ▪ Angiosperms also contain vessel elements with perforations for water transport. Phloem Structure Phloem is complex tissue containing two types of specialized cells: 1. Sieve-tube elements: long, thin cells with perforated ends called sieve plates 2. Companion cells maintain the cytoplasm and plasma membrane of sieve-tube elements Plant Immune System Plant Immune System vs. Animal Immune System: Analogy: Plants face threats similar to animals: herbivores (external) and pathogens (internal); but plants cant move. Plants employ various defense strategies: Physical Barriers: Cell walls, waxy cuticles, and trichomes (hair-like structures) Chemical Defenses: wide range of antimicrobial compounds to deter or kill invaders. Hypersensitive Response (HR): Localized cell death at the site of infection to limit pathogen spread. Systemic Acquired Resistance (SAR): whole-plant defense response triggered by local infection, leading to enhanced resistance in distant tissues. 34.3 Primary Growth Extends the Plant Body Primary Growth: – Increases length of roots and shoots. Meristems: – Undifferentiated cells capable of mitosis. Apical Meristems: – Found at root and shoot tips, responsible for primary growth. Primary Plant Body: – Composed of dermal, ground, and vascular tissue systems. Apical Meristems and Primary Meristems Apical Meristems: – Give rise to three primary meristems. Primary Meristems: – Protoderm (dermal tissue), Ground meristem (ground tissue), Procambium (vascular tissue). Tissue Systems: – Dermal, ground, and vascular. Primary Plant Body Is Composed of the Dermal, Ground, and Vascular Tissue Systems Stems Extend via Growth of Apical Meristems and Cell Elongation Zone of Cellular Division: Contains apical meristem, protoderm, ground meristem, and procambium. Zone of Cellular Elongation: Cells increase in length. Zone of Cellular Maturation: Cells differentiate into dermal, vascular, or ground tissue. Roots Extend into the Soil via Growth of Apical Meristems and Cell Elongation Tissue Systems in Stems Have Distinct Arrangements 34.4 Secondary Growth and Cambia Secondary Growth: – Increases width of roots and shoots. Components: – Cambium and apical meristems. Cambium Initiation: – In woody eudicot stem. Cambia in Secondary Growth: – Vascular cambium and cork cambium. Components of Secondary Growth Meristematic Mature Tissue Direction of Mature Cell Mature Tissue Tissue Growth Composition Function Cork Cork Produced to Cork cells Protection (part of Cambium the outside bark) Vascular Secondary Produced to Sieve-tube elements, Transport of sugars, Cambium phloem the outside companion cells, and amino acids, sclerenchyma cells hormones, etc. (fibers) Vascular Secondary xylem Produced to Tracheids, vessels, Transport of water Cambium (also called wood) the inside parenchyma cells and ions; structural (arranged in rays) and support sclerenchyma cells (fibers) Cambia Responsible for Secondary Growth Initiation of Secondary Growth in Trees Trunk Structure and Growth Rings: Heartwood: – Older, innermost secondary xylem with protective compounds like resins and gums. Sapwood: – Light-colored outer xylem. Vascular Cambium Dormancy: – Stops growing during dry or cold seasons. Annual Growth Rings: – Formed with alternating early (wide) and late (narrow) wood. Dendroecology: – Science of tree growth rings. Example: – Ring number indicates age; wide rings represent wet years, narrow rings signify drought years. Trunk Structure and Growth Rings: