Thursday, February 23rd

Plant Growth and Structure

The Plant Body

• The plant body is divided into two main parts• 1. Roots: Anchors plants in the ground and

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