Thursday February 23 rd Plant Growth and Structure

Thursday, February 23 rd Plant Growth and Structure

The Plant Body • The plant body is divided into two main parts • 1. Roots: Anchors plants in the ground absorbs water and minerals • 2. Shoots: above ground framework for leaves, flowers, and fruits

Two form of Root Systems • Taproot • Fibrous Root System

Taproot • Large central root (primary root) off which smaller roots (lateral roots) grow • Taproots have small surface area so they are not as effective at absorbing water and nutrients • However, the large root can store nutrients and water – Think of a CARROT • Advantage to plants that grow in regions of minimal water

Taproot

Fibrous Root System • Composed of a diffuse system of roots, no single main root • Greater surface area and extends further absorbing more water and nutrients • Ex: ferns and grass

Fibrous Root System

Root System Parts & Functions • Primary Root - Central root of plant, extending from the stem • Lateral roots - Roots growing directly off the primary root • Root Hairs - Hairs that extend from the root and greatly increase surface area

Apical Root Meristem • Apical Root Meristem - Cell growth at the tip of the primary root, required for growth of the plant body • Root Cap – protects the root, these cells are sloughed off and replaced as the root moves through the soil

• Meristem Cells are not differentiated yet – they are like stem cells for plants • When they divide, they produce another meristem cell and a differentiated cell

Types of Growth • Primary growth – results in increase of length (height in shoots, depth in roots) • Secondary Growth – result in increase of diameter

Vascular Tissue (in roots and shoots) • Cells arranged to form tubes through which water and nutrients can flow through the plant • Two Types: – Xylem conveys water and minerals up the root – Phloem conveys the product of photosynthesis down from the leaves

Structures in the Stem • The stem provides structural support for the plants leaves, flowers, and fruits • Nodes - the point where the leaves are connected to the stem • Internodes – stretches of stem between the nodes

Structures in the Stem • Terminal Buds - Underdeveloped shoot at the tip of a stem • Auxiliary buds - Underdeveloped shoot where petiole (joins stem to leaf) meets the stem • Apical Shoot Meristem - Cell growth at the tip of the stem

Leaf Structure • Leaf - primary site of photosynthesis. Includes petiole • Cuticle -waxy coating on plants that prevent water loss and also protects the plant from bacteria & viruses • Stomata - tiny pores in the leaves surface that allows substances (water, oxygen, carbon dioxide) to pass through the plant

Stoma (singular for Stomata) Guard Cell

Guard Cell • Guard Cell – sausage-shaped cells that look like a mouth. They control whether the stomata is open or closed

Page 730 In Your Book • There is a diagram of a plant body I want you to sketch in your journal. • You should label the following structures: • “Shoot Apex” and “Root Apex” where Apical Meristem cells are located • Node, Internode, Leaf, Petiole, Primary Root, Lateral root, Root System, Shoot System

Pg 730

Auxin promotes elongation

Gravitropism

Gravitropism

Gibberellin

Ethylene • Bananas are picked when they’re green so they are easier to ship. • Once they reach a storage location close to where they’re going to be sold, they are artificially ripened using Ethylene

Pg 730