Horticulture

23 Oct 2015

Entry Task

Take out…

• Study Guide

• Entry Task• Learning Objectives• Housekeeping• Group Text Analysis• Greenhouse

Agenda

Housekeeping

Quiz 4 tomorrow, 24 Nov.• Collect study guide

Half day on Wednesday, 25 Nov.• Schedule posted• Turn in notebooks

Turkey Day Holiday, 26 & 27 Nov.• NO SCHOOL

Learning Objective(s)

Investigate the structures and functions of plant tissues, and factors affecting plant growth.

Examine the diversity of vascular plants, including their structures, internal transport systems, and their role in maintaining biodiversity.

Plant Organs & Their Functions

Plant Structure and Function

Plant Cell Types• Parenchyma• Collenchyma• Sclerenchyma

Plant Tissues• Meristematic• Dermal• Ground• Vascular

Plant Structure and Function

Plant Organs• Roots• Stems• Leaves

Plant Transport• Water• Nutrients

Compare & Contrast Monocots & Dicots

Roots

Roots serve 3 functions:

• They take in water and dissolved minerals• They anchor the plant• They store carbohydrates, water, & other nutrients

Roots

The root system can be so large that it makes up more than half the plant’s mass.

• Most plant roots grow 0.5m – 5m down into the soil.

- Into what layer of soil?

- Subsoil

• In dryer climates they can go as deep as 50m.

Roots

The root system can be so large that it makes up more than half the plant’s mass.

• Other plants have relatively shallow branching roots.

- 15m in all directions

Roots

Root structure and function

• Root Cap

- Covers the tip of the root

- Made of parenchyma cells

- Protects growing tissue as root extends into the ground

- Produces slimy substance that helps reduce friction

Roots

Root structure and function

• Apical meristem

- Produces new cells that develop into different tissues

- Replaces cells removed by friction

- Increase the length of the root

Roots

Outer Root Layers

• Dermal Tissue

- Epidermal cells produces root hairs increasing surface area to absorb water & minerals

• Cortex

- Transports & stores water, minerals, & food

- All materials must pass through the cortex to enter the vascular tissue

Roots

Outer Root Layers

• Endodermis

- Inside edge of the cortex

- Surrounded by waterproof band (“Caspirian Strip”)

- Acts as a control point for materials entering the vascular system.

Roots

Inner Root Layers

• Center of the root

• Vascular tissues

- Xylem

- Phloem

- Arrangement is different in monocots & dicots

Roots

Inner Root Layers

• Monocots

- Xylem forms rings around central core

- Core of the cells is called the “pith”

- Phloem cells surrounds the xylem

• Dicots

- Xylem forms an X or star shape

- Phloem cells are between the arms of the star

Roots

Types of Root Systems

• Taproot

- Thick root with smaller lateral branching roots

- Some plant use taproot to store food (carrots)

• Fibrous Root

- Many smaller branching roots

- Usually the same size & grow from a central point

- Some modified to provide extra support or store food

- Some aquatic plant roots have aerenchyma (spongy tissue that allows the passage of oxygen)

Question Worksheet

Stems

Leaves

Differentiating Flowering Plants: Dicots & Monocots

* Posted on webpage under /Horticulture Assignments

Transport in Plants

Water and dissolved nutrients move through plants by 3 processes.

• Diffusion• Osmosis• Active Transport

Transport in Plants

Diffusion

• Net movement of particles from area of high concentration to low concentration.

• Occurs till the concentration of both side is equal.

Osmosis

• Movement of water molecules to either side of membrane until concentration is balanced

Transport in Plants

Active Transport

• Active movement of sugars & nutrients across cell membranes

• Requires energy

Transport in Xylem

Xylem transports water through the roots up to the stem by osmosis.

Within the stem water moves by diffusion.

Long distance transport in plants is accomplished by 2 processes.• Root pressure = positive pressure = pushing• Transpirational pull = negative pressure = pulling

Transport in Xylem

Root Pressure

• Mechanism that pushes water & minerals up the plant.• Occurs because of positive pressure.• Guttation

- process where droplets form on leaves due to high root pressure, humidity & low rate of transpiration.

Transport in Xylem

Minerals move into roots against the concentration gradient through active transport.

• The higher concentration of dissolved minerals causes more water to move in by osmosis.

• Creating positive pressure

Transport in Xylem

Transpirational Pull

• Creates negative pressure the strongest force for long distance transport of water & dissolved minerals.

• Transpiration = loss of water due to evaporation through the stomata of the leaves.

• Cohesion = force of attraction between water molecules.

• Adhesion = water molecules adhere, or stick, to the xylem walls.

Transport in Phloem

Translocation

• Transport of sucrose & other organic molecules through the phloem.