Lecture 10 Plant Growth .pptx

How does structure fi t function in vascular plants? • Natural selection has molded plant structure to support function at the organ, tissue, and cellular levels © 2021 Pearson Education Ltd. CONCEPT 35.1: Plants have a hierarchical organization consisting of organs, tissues, and cells • Plant or...

How does structure fi t function in vascular plants? • Natural selection has molded plant structure to support function at the organ, tissue, and cellular levels © 2021 Pearson Education Ltd. CONCEPT 35.1: Plants have a hierarchical organization consisting of organs, tissues, and cells • Plant organs are composed of tissues, which in turn are composed of cells • A cell is the fundamental unit of life • A tissue is a group of cells consisting of one or more cell types that together perform a specialized function • An organ consists of several types of tissues that together carry out particular functions © 2021 Pearson Education Ltd. Vascular Plant Organs: Roots, Stems, and Leaves • The basic morphology of vascular plants reflects adaptations to draw nutrients from above and below the ground • Plants take up water and minerals from below ground • Plants take up C0 2 and light from above ground © 2021 Pearson Education Ltd. • Three basic organs evolved to facilitate efficient resource acquisition: roots, stems, and leaves • They are organized into a root system and a shoot system • The shoot system includes stems and leaves © 2021 Pearson Education Ltd. • Roots rely on sugar produced by photosynthesis in the shoot system • Shoots rely on water and minerals absorbed by the root system © 2021 Pearson Education Ltd. Roots • A root is an organ with important functions: - Anchoring the plant - Absorbing minerals and water - Storing carbohydrates • The primary root is the first to emerge from the seed • Lateral roots branch off from the primary root improving anchorage and water absorption © 2021 Pearson Education Ltd. Stems • A stem is a plant organ bearing leaves and buds • Stems consist of an alternating system of nodes and internodes • Nodes are the points at which leaves are attached • lnternodes are the stem segments between nodes © 2021 Pearson Education Ltd. • The growing shoot tip, or apical bud, causes elongation of a young shoot • An axillary bud is a structure that has the potential to form a lateral branch, thorn, or flower © 2021 Pearson Education Ltd. • The primary function of the stem is to elongate and orient the shoot to maximize photosynthesis • Many plants have modified stems that perform alternate functions © 2021 Pearson Education Ltd. Leaves • The leaf is the main photosynthetic organ of most vascular plants • Leaves intercept light, exchange gases, dissipate heat, and defend against herbivores and pathogens • A leaf generally consists of a flattened blade and a stalk, the petiole, which joins the leaf to the stem © 2021 Pearson Education Ltd. • Monocots and eudicots differ in the arrangement of veins, the vascular tissue of leaves - Most monocots have parallel veins - Most eudicots have branching veins • Leaf shape, arrangement of veins, and spatial pattern of leaves can help with plant identification • Leaf shape may be simple or compound © 2021 Pearson Education Ltd. Dermal, Vascular, and Ground Tissues • Roots, stems, and leaves are composed of three tissue types: dermal, vascular, and ground tissues • Each of these tissue types forms a tissue system that is continuous throughout the plant • The characteristics of the tissues and their spatial relationships vary in different organs © 2021 Pearson Education Ltd. • Dermal tissue serves as a protective outer coating • In nonwoody plants, it is usually a single tissue layer called the epidermis • A waxy cuticle covers the epidermis and protects leaves and most stems from water loss • A protective layer called the periderm replaces the epidermis in older regions of woody stems and roots © 2021 Pearson Education Ltd. • Guard cells are specialized dermal cells that facilitate gas exchange in shoots • Trichomes are hairlike outgrowths of epidermal cells that help reduce water loss, reflect light, and defend against insects © 2021 Pearson Education Ltd. • Vascular tissue facilitates the transport of materials through the plant and provides mechanical support • Vascular tissue includes xylem and phloem - Xylem conducts water and dissolved minerals upward from roots into the shoots - Phloem transports sugars from where they are made (primarily leaves) to actively growing parts of the plant or storage structures © 2021 Pearson Education Ltd. • Tissue that are neither dermal nor vascular is ground tissue • Ground tissue internal to the vascular tissue is pith; ground tissue outside the vascular tissue is cortex • Ground tissue includes cells specialized for storage, photosynthesis, support, and shortdistance transport © 2021 Pearson Education Ltd. Common Types of Plant Cells • Plant cells undergo cell differentiation; that is, specialization in structure and function, during development • The structural adaptations of various types of plant cells make their specific functions possible © 2021 Pearson Education Ltd. • The major types of plant cells are - Parenchyma Collenchyma Sclerenchyma Water-conducting cells of the xylem Sugar-conducting cells of the phloem © 2021 Pearson Education Ltd. Parenchyma Cells • Mature parenchyma cells - Have thin and flexible primary walls Generally lack secondary walls Have a large central vacuole Perform most of the metabolic functions Retain the ability to divide and differentiate © 2021 Pearson Education Ltd. Collenchyma Cells • Collenchyma cells are grouped in strands and help support young parts of the plant shoot • They have unevenly thickened primary cell walls • They are living at maturity • These cells provide flexible support without restraining growth © 2021 Pearson Education Ltd. Sclerenchyma Cells • Sclerenchyma cells are rigid cells with secondary cell walls containing lignin, a strengthening polymer, for support • Many are dead at maturity; the rigid cell walls remain to support the plant © 2021 Pearson Education Ltd. CONCEPT 35.2: Different meristems generate new cells for primary and secondary growth • A plant can grow throughout its life; this is called indeterminate growth • Continuous growth is possible due to the activity of meristems, undifferentiated tissues composed of dividing cells • Most animals and some plant organs cease to grow at a certain size; this is called determinate growth © 2021 Pearson Education Ltd. • There are two main types of meristems: apical meristems and lateral meristems • Apical meristems are located at the tips of roots and shoots • Cells of the apical meristems allow for elongation of shoots and roots, a process called primary growth © 2021 Pearson Education Ltd.