LB

7 Secondary Thickening

Overview of Growth

Understanding the concept of growth in plants, including both primary and secondary growth processes.

Stem Structure

Diagram of Herbaceous Dicot Stem: Understanding the anatomy of the stem.Key Components:

  • Cambium: Layer responsible for secondary growth.

  • Epidermis: Outer protective layer.

  • Bundle Cap: Structure supporting vascular bundles.

  • Medullary Ray: Storage and transport structure.

  • Xylem/Phloem: Vascular tissues for water and nutrient transport.

  • Pith: Central storage region.

Helianthus (Sunflower) Stem Cross Section

Components of Dicot Stem:

  • Fibers: Structural support.

  • Collenchyma: Provides flexible support.

  • Vascular Bundles: Groupings of xylem and phloem.

Root Structure

Anatomy to Note:

  • Cortex, Phloem, Metaxylem, Protoxylem, Pith: Understanding their roles in the root system.

Diagram of Root TS

Overview of Root Structure:

  • Cambium, Epidermis, Primary Phloem, Pericycle, Endodermis, Cortex, Primary Xylem.Analyze function of each structure in sustaining plant life.

Root Anatomy Details

Detailed roles of:

  • Pericycle: Layer giving rise to lateral roots.

  • Primary Phloem and Xylem: Transportation of nutrients and water.

  • Endodermis and Cortex: Key in regulating water and nutrient flow.

Vascular Cylinder/Stele Configuration

  • Protostele: Simplest stele with xylem in center, surrounded by phloem and pericycle.

  • Endodermis: Regulates water flow from the cortex.

Vascular Tissue Formation

Primary Xylem Formation:

  • Formed by actively dividing cells at root/shoot tips (apical meristems).

  • Vascular cambium gives rise to secondary xylem (metaxylem).

  • Two conducting cell types: Tracheids and Vessel Elements.

Phloem Details

Phloem Composition:

  • Types of conducting cells: Sieve cells and sieve tube members.

  • "Sieve element" encompasses both types.

Cross Section of Monocot Stem

  • Analyze structural differences from dicot stems, focusing on vascular bundle arrangement.

Stem Structure Details

  • Analysis of airflow shipping within xylem vessels, phloem sieve tubes, and companion cells, essential for plant transport.

Bud and Growth Terminology

Key Concepts:

  • Terminal Bud: Growth point of the shoot.

  • Growth Features: Epidermis, Primary Phloem, Secondary Xylem, Bark, Periderm.

Components in Root Structure

Components labelled:

  • Procambium

  • Vascular Bundle

  • Cambium

  • Primary Xylem

  • Pith

  • Primary Phloem

  • Cortex

  • Epidermis

Secondary Growth Overview

  • Ground Tissue Formation: Role in structural support and resource storage in stems.

Secondary Thickening Process

  • Vascular Cambium: Increases girth through secondary xylem and phloem production.

  • Formation of woody structures visible as tree rings.

Growth Layer Analysis

Layers Over Time:

  • First-year and second-year growth structures, including cork and cambium development.

Growth Process Overview

  • Distinction between primary and secondary growth in stems, including:

    • Apical and lateral meristems role in girth and length increases.

Vascular Cambium Functionality

  • Vascular cambium's contribution to thickening stems via production of secondary tissues.

Annual Growth Rings

Understanding Annual Rings:

  • Contributions of secondary xylem and phloem in indicating growth conditions.

Monocotyledons Growth Characteristics

Monocot Characteristics:

  • Lack of significant growth in diameter and how parenchyma cells can still divide.

Secondary Meristem Functionality

  • Unique features of some plants like Dracaena with secondary meristems contributing to parenchyma production and vascular structure formation.

Tropiculture

  • Overview of tropiculture as a method of enhancing plant growth and agricultural practices.