Roots, Stems, and Leaves Specialized Tissues In Plants A.Seed Plant Structure 1. Roots 2. Stems 3. Leaves B. Plant Tissue Systems C. Dermal Tissue D.Vascular Tissue 1. Xylem 2. Phloem E. Ground Tissue F. Plant Growth and Meristematic Tissue Seed Plant Structure • The cells of seed plants are organized into tissues and organs. • The three main plant organs are roots, stems, and leaves. – Roots absorb water and dissolve nutrients and anchor plants in the ground. – Stems support the plant body and transport materials throughout the plant. – Leaves are the main organs of photosynthesis. They also function in gas exchange. Root, Stem, and Leaf Tissues Leaf Stem Root Dermal tissue Vascular tissue Ground tissue Plant Tissue Systems • Within the roots, stems, and leaves are specialized tissue systems. The three main tissue systems: – Dermal tissue is like the skin of a plant. It protects the plant and prevents water loss. – Vascular tissue consists of xylem (move water throughout the plant) and phloem (moves sugars and other materials throughout the plant). – Ground tissue is made up of all of the cells that lie between dermal and vascular tissues. (made up of 3 kinds of cells) • Parenchyma cells: function in photosynthesis and storage • Collenchyma cells: help support larger plants • Sclerenchyma cells: make ground tissue tough and strong Plant Tissue Systems Cont. • A fourth kind of tissue, meristematic tissue, is responsible for plant growth. – Meristematic tissue is the only plant tissue that produces new cells by mitosis. – The tips of stems and roots are made of meristematic tissue. Concept Map Plant Tissues include Dermal tissue Meristematic tissue includes Epidermal cells Ground tissue includes Xylem includes Tracheids Vascular tissue Vessel elements includes Phloem Parenchyma cells includes Sieve tube elements Companion cells Collenchyma cells Schlerenchyma cells Roots • The two main types of roots are taproots and fibrous roots. • Taproots: the primary root grows long and thick, while the secondary roots stay small. • Fibrous roots: secondary roots that grow and branch out • Roots have two main functions – To anchor a plant in the ground – To absorb water and dissolved nutrients form the soil Taproots and Fibrous Roots • Taproots (Carrots) Fibrous Roots (Grasses) The Structure of a Root Epidermis Endodermis Root hairs Ground tissue (cortex) Phloem Xylem Vascular Cylinder Ground tissue (cortex) Epidermis Endodermis Vascular cylinder Zone of maturation Zone of elongation Apical meristem Root cap Cross Section of Plant Root (magnification: 40x) Stems • Stems have three important functions – To produce leaves, branches, and flowers – To hold leaves up to the sunlight – To carry water and nutrients between the roots and leaves Plant stems grow in two ways Comparing Primary and Secondary Growth of Stems Characteristics Primary Growth Secondary Growth Where It Occurs At ends of plants In stem Effect on Plant Increases plant length Increases stem width How It Is Produced By cell division in the apical By cell division in meristem meristems other than the apical meristem Leaves • The structure of a leaf is optimized for absorbing light and carrying out photosynthesis. • To collect sunlight, most leaves have thin, flattened sections called blades. • Plants can lose water out of their leaves as they exchange gases with the air (transpiration). – To prevent major water loss plants allow air in and out of their waterproof covering only through small openings called stomata. – Plants keep their stomata open just enough to allow photosynthesis to take place but not so much that they lose an excessive amount of water. Transpiration A B Evaporation of water molecules out of leaves. Pull of water molecules upward from the roots. Blades On Leaves The Internal Structure of a Leaf Cuticle Veins Epidermis Palisade mesophyll Xylem Phloem Spongy mesophyll Epidermis Stoma Guard cells Vein Transport in Plants • Forces of Attraction • Molecules of a similar substance are attracted to one another by a force called cohesion. • Molecules of different substances are attracted to one another by a force called adhesion. Transport In Plants Phloem Xylem Sugar molecules Source cell Movement of water Movement of sugar Sink cell