16.3 Water and Food Transport pg. 545- 550

1. 16.3 Water and Food Transportpg. 545- 550 By: Fariha, Ekua, and Mathew

2. Introduction • The xylem is found in vascular plants • The function is to transport water and minerals from the soil to all parts of the plant. • The phloem is to transport sugars from leaves to all parts of the plant. • The actual carrying of the water and sugars from the xylem and phloem isn’t fully understood yet

3. Water Transport in Vascular Plants In the Root: • The roots of the plant called root hairs absorb the essential minerals and transport it to the plant. • When the minerals reach the epidermis it enters the wax coated endodermis where the minerals cannot go back into the soil • The minerals create xylem sap which is a hypertonic. After it enters the root by osmosis. The water and dissolved minerals creates pressure and pushes the sap up the xylem. This is called root pressure and it in some plants such as tomatoes. • The root pressure is able to push water up to a few meters. But some plants like trees can push it up to 100 meters.

4. In the Stem: • In the stem water clings to surfaces that aren’t oily and is known as adhesion. Water can stick to itself and is known as cohesion. It is because of the hydrogen bonding between adjacent water molecules, they have a strong force of attraction. • Cohesion is the ability of water to stick to itself • There are strong attractions because the hydrogen bonding between adjacent water molecules • Xylem vessels don’t contain much water • The cohesion of water molecules in the xylem vessel is the reason the column holds together • If a “pull” occurs at the top of the column there would be enough strength to pull water from its roots • This pull comes from the leaves through a process call leaf pull or transpiration pull

5. In the Leaves: • Transpiration causes water loss • Evaporation of water molecules during transpiration causes a “pull” on the adjacent molecule, the next one pulls on another and in a “chain reaction” all the way up to the root hairs • The plant uses its surrounding heat energy to pull water from the roots to the top • Xylem sap movements depend on the rate of transpiration • Low temp.= low rate • High temp.= higher rate • The faster water evaporates from the leaves, the faster sap will rise • Theory- Scientists estimated that the pulling force given off by transpiration pull, combined with cohesion forces, can transport water to the top of trees three times higher that the tallest known trees

6. The Flow of Water from Roots to Leaves

7. Product Derived from Xylem Sap: • Xylem sap of the sugar maple tree is used to make syrup • During early spring these trees convert starches in the roots into sugars and send them up the xylem to the branches • Holes are tapped into the xylem to collect the sap • The sap is boiled down to remove excess water • It takes 50 L of sap to make 1 L of syrup ← A sugar maple tree Collection of sap→

8. Food transport in Vascular Plants • The exact source of food transport is unknown • It’s hard to explain how exactly food is moved through plants due to the fact that the phloem sieve tubes cells are living cells with cytoplasm • Xylem vessel cells are dead cells and make it easier to explain how water moves up and down the hollow tubes as well as sugars this theory is called the pressure flow theory • Leaf cells are called the source, the storage cells are called the sink • Sugars are pumped into the tube by active transport which causes a hypertonic solution • This solution causes water to move through osmosis into the tube cells • In the root the sugars are moved out of the tube and in the suki

9. Food Transport in Plants

10. Water and Food Transport in Bryophytes • Bryophytes are non vascular that do not have xylem or phlegm • There are three groups of bryophytes, masses, liverworts, and hornworts • Bryophytes grow on rocks and on tree barks as well as soil • Due to not having any xylem they grow in wet damp shaded environments • Water moves through the plant also through mitosis and capillary action • They can only grow up to two cm • They do not have leaves, stems or roots • Rhizoids are there to anchor the plant • They are responsible for manufacturing their own sugars since it lacks phlegm

11. Thank You