Transport in Living Things Chapter 25 Chapter 25.5 Transport System in Flowering Plants

What did we learn? Transport system of plants Water roots osmosis Consists of Phloem Xylem Is a living tissue made up of sieve tubes and companion cells Is a continuous hollow tube with lignified walls enters Water http://www.youtube.com/watch?v=At1BJJDcXhk&feature=related http://www.youtube.com/watch?v=At1BJJDcXhk Transports food substances roots Transports water and mineral salts via osmosis

Lesson Objectives At the end of the lesson, You should be able to: relate the structure and functions of root hairs to their surface area, and to water and ion uptake state that transpiration is the loss of water vapour from the stomata define the term translocation as the transport of food in the phloem tissue identify the positions of xylem vessels and phloem in sections of a typical dicotyledonous stem and leaf, under the light microscope, and state their functions relate the structure and functions of root hairs to their surface area, and to water and ion uptake state that transpiration is the loss of water vapour from the stomata

Transport of mineral salts

Plant Profile What process is being used to take in mineral salts? Name: Claudia Owner: Farmer A Characteristics: Is watered and fertilizer is added everyday. 5

Transport of mineral salts Plasma membrane of root hair cell Sap in root hair Soil solution Mineral concentration low Mineral concentration high Mineral salts Diffusion

Plant Profile What process is being used to take in mineral salts? Name: Lydia Owner: No one Characteristics: No one takes care of it and the soil is dry and mineral- poor. 7

Transport of mineral salts Qn: Can the root hair absorb ions if the concentration is higher in the root hair sap compared to the soil solution? Yes!!! Plasma membrane of root hair cell Sap in root hair Soil solution Mineral concentration high Mineral concentration low Mineral salts? Active transport

Translocation Definition: It is the transport of manufactured food substances such as sugars and amino acids in plants. How can we show that the phloem carries materials from the leaves to other parts of the plant?

“Ringing” experiment Take the branch of a woody plant Remove a ring of bark from around the main stem. Put it into water Observe it over a few weeks

“Ringing” experiment Region with bark removed Unringed twig Water A B

After a few weeks… The part of the stem just above the cut region will swell

Transpiration Definition of transpiration: The loss of water vapour from the aerial parts of the plant, especially through the stomata of the leaves Just as in our original example of water potential, the water moves from the intercellular spaces to the atmosphere. Water is lost from cells to the intercellular spaces, and these cells then being at a lower (more negative) water potential than their neighbours will abstract water from them. This continues across the leaf until it reaches the bundle sheath cells. These abstract water from the xylem. Water is highly cohesive. The water molecules are bonded to each other by hydrogen bonds, and are thus very cohesive. Experiments to demonstrate the cohesive strength of water have generally put the strength of bonding of water molecules at several hundred atmospheres. (This only works in the absence of contaminating gasses which will come out of solution under vacuum, hence columns of water do get broken in the plant under normal physiological conditions). The entire column of water therefore is dragged up, and the reduction in pressure potential in roots literally sucks water in. Again this is propagated across the pith of the root up to the endodermis.

Similarity? Functions of transpiration: Cool the plant; prevent scorching Facilitates the lifting of water and mineral salts from roots to leaves

Transpiration pull Leaf cells lose water concentrated cell sap = lower water potential Evaporation of water from leaves Draw water from cells deeper inside the leaf by osmosis Cells remove water from xylem vessels Creates a transpiration pull The evaporation of water from leaves result in a suction force which pulls water up the xylem vessels Suction force due to transpiration is transpiration pull

Factors affecting transpiration rate Humidity of air Temperature of air Strong wind Light Size and shape of leaves (surface area)

Summary Food substances Water Mineral salts roots roots leaf via enters Water roots via Mineral salts enters roots Food substances Diffuses out of Travels from leaf Leaves or aerial parts of the plant to Other parts of the plant via Osmosis Diffusion Active transport via Is the transport of manufactured food substances such as sugars and amino acids in the plants Transpiration Is the loss of water vapour from the aerial parts of the plant Translocation