Transport in Living Things

Chapter 25Chapter 25.5 Transport

System in Flowering Plants

What did we learn?Movement of substances

Diffusion Osmosis

Passive process Active process

Net movement of molecules from a region of higher concentration to a region of lower concentration

Net movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane

Active Transport

Movement of molecules from a region of lower concentration to a region of higher concentration with the use of energy

Carbon dioxide and

oxygen inside leaves

Gaseous exchange in the lungs

Transport of water into roots

Transport of mineral

salts into the roots

Lesson ObjectivesAt the end of the lesson,You should be able to:• State what the vascular bundle consists of• Describe the structure and function of xylem and

phloem• Identify the position of xylem vessels and

phloem in sections of the stem• relate the structure and functions of root hairs to

their surface area, and to water and ion uptake

Looking at the rose…

• How do you turn a white flower into a blue one?

• How does the coloured water travel up the stem to the flower?

Vascular tissues

1. Xylem 2. Phloem

Xylem tissueStructure• composed of hollow,

nonliving cells (continuous lumen)

• Lignified wallsFunction• transports water and mineral

salts from roots → stem → leaves

• provides mechanical support to plant

Structure of Xylem

QUESTION

• How is the straw similar to the xylem?

Phloem tissue

Structure• Living cellsFunction• Transports manufactured

food (sucrose and amino acids), usually from leaves → other parts of the plant

Identifying a vascular bundle

Identifying a vascular bundle in a dicotyledonous stem

A vascular bundle

cambium

Transverse section of a stem

Why do you think the xylem is positioned on the inside?

How to distinguish xylem vessels from phloem in microscopic slides?

Xylem vessels have• Thicker walls

- due to lignified walls (either annular, spiral or pitted) to provide mechanical support to the plant

• Larger lumen compared to phloem

• Xylem vessels have a darker stain.

Locate the xylem and phloem

phloem

xylem

Leaf structure

phloem

xylem

Transport of water

Structure of root• Presence of Root hairs• Increased surface area

Function of root• Absorb water and mineral salts from the surroundings• Water absorbed from the root enters the xylem

Entry of water into the plant

Thin film around particle = dilute solution of mineral salts

Entry of water from soil

Sap in root hair Soil solution

Strong solution of sugars and salts

Dilute solution of mineral salts

Low water potential

Higher water potential

Plasma membrane of root hair cell

H2O

Osmosis

Transport of water from root hair → xylem

Low water potential

High water potential

Transport of mineral salts

Transport of mineral salts

Sap in root hair Soil solution

Plasma membrane of root hair cell

Mineral concentration low

Mineral concentration high

Mineral salts

Diffusion

Qn: Can the root hair absorb ions if the concentration is higher in the root hair sap compared to the soil solution?

Transport of mineral salts

Sap in root hair Soil solution

Plasma membrane of root hair cell

Mineral concentration high

Mineral concentration low

Mineral salts?

Active transport

Yes!!!

Summary

Xylem Phloem

Plant Transport system

transports

Water containing dissolved mineral salts from the roots to the leaves

Manufactured food substances (eg. sugars) from the leaves to the other parts of the plant

where

Water moves into the root hair cell via OSMOSIS

Consists of

Mineral salts move into the root hair cell

via Diffusion OR ACTIVE TRANSPORT

In the next lesson…

We will be learning about• what is transpiration• what is translocation

• MINI QUIZ!