Transport in Plants
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a. Plants don’t have a __; food is transported through the plant’s __
- circulatory system
- vascular tissue (xylem and phloem)
Three types of Transport
- i. Gas exchange (at leaf)
- ii. Transpiration: One that occurs at level of root, moving dissolved materials in and up through xylem
- iii. Translocation: movement of sugars or organic material that was made by plant that occurs through phloem
a. Occurs at level of __through __
b. Explain it in terms of guard cells
- When the guard cells are turgid, the stoma is open, allowing for material to leave the plant (water, carbon dioxide, oxygen)causing material and gases to leave/ enter plant
What makes the guard cells turgd?
- i. What opens the guard cells is an ATP proton pump
- ii. Uses energy and the proton pump
- iii. ACTIVE TRANSPORT OF POTASSIUM IONS INTO THE CELLS
- iv. When potassium enters the cells, water osmotically follows due to concentraition
- 1. under certain conditions, potassium ions are transported into guard cells
- 2. the cell BLOWS UP= TURGIDà space opens
What closes stoma?
i. water and potassium leave
What controls opening?
- i. Circadian rhythm
- 1. Biological clock that causes them to become turgid and collapse
- 2. Light
- 3. Low CO2
What controls closing?
- a. STRESS
- i. If plant in threat of dehydration, the stoma will not open up
- ii. If there is a lot of carbon dioxide in the leaf, the stoma will stay closed
- iii. Abscisic acid
- 1. Released in times of stress of plant, causing it to keep stomata closed
Good Conditions for the plant
- i. Enough water vapor
- ii. Light
- iii. Circadian rhythm
- iv. Low CO2
- a. Movement of water and minerals from the soil to the leaf
- a. Once into vascular stele, it then can move up the xylem and the xylem forms a continuous tube network from the root all the way up to the leaf a. Only up
What is associated with transpiratoin?
- a. Specialized cells in xylem that are responsible for movement of water and dissolved minerals
- i. Tracheids and vessel elements
- 1. Dead at maturity; there’s nothing in them (no cell organelles, etc.)
What causes movement in transpiration?
- i. Three pressures: transpirational pull, root pressure, and cohesion/ adhesion properties of water
- ii. Transpirational pull
- iii. Root pressure
Explain transpirational pull in terms of transpiration
- 1. If stoma are opened at top at the leaves and it’s losing water vapor, its going to force the plant to want more water
- 2. Very weak; generally plays no role in large trees or bushes, but it does cause a pull at the roots because it wants to make more water in, creating a pressure that wants to get water up
- 3. Due to loss of water vapor at the top of the plant (at the stoma of the leaves)
Root Pressure in terms of Transpiration
- 1. Results from the inward active transport of solutes from the soil by root cells
- 2. Due to movement of solutes into the root and water osmotically follows
- 3. As more water comes in, it’ll push up those vessels and tracheids
- 4. The greater the solute concentration, the more is absorbed, the more water comes in and the more pressure is created
- 5. Force that is greater than transpirational pull, but generally weak
- 6. Cause push through cortex, up stele and into plants
Cohesion and Adhesions in terms of transpiration
- 1. Water molecules stick together (forming a continuous sheet)= COHESIVE NATURE OF WATER
- 2. Water also adheres to the lining of tissues
- a. Once it enters the stele, it forms a continuous flow of molecules up that xylem because it’s cohesive and adhesive
- i. Adheres to xylem and it’s being pushed up as a continuous column of water
- 1. NOT BITS AND PIECES
- 2. In that water are the dissolved minerals
- 3. GREATEST EFFECT ON MOVING THROUGH XYLEM TO THE TOP OF THE PLANT
- a. Movement of organic material made by the plant through the plant that ocfurs in phloem
- b. It is movement in all different directions
- i. In phloem, things can move up, down, sides,
Characteristics of translocation
- a. in terms of movement through phloem, there are the source and sink
- i. source: where the organic material was loaded into phloem
- 1. it can be the root, stem, or leaf
- ii. sink: where it’s unloaded
- 1. takes it out of the phloem at the sink; maybe stored in the stem and now the leaf wants it (do you see? It’s not stationary)
Unlike xylem, what are phloem?
- a. phloem cells are alive at maturity
- i. cells that are unique cells are sieve cells/ tube elements and companion/ albuminous cells
- 1. have to be alive in order for translocation to occur
What does translocation involve?
- a. involves the active transport of the organic material into the companion cells into the sieve cell
- i. in the sink, it’s active transport out
- 1. active transport loads and unloads sugars into and out of phloem
What is in the cortex of the root?
- endodermis-Casparian strip
- stele (central part of the root containing the vascular tissue)
Nutrients are in __.
Absorption of minerals is based on what?
- •Absorption of minerals independent of rates of water absorption.
- •Each mineral moves into the root at a rate determined by:
- 1. its concentration
- 2. ease it can passively penetrate cell membranes or go through ion channels
- 3. available carriers
What does the xylem tissue contain?
- tracheids and vessel elements
- living parenchyma
What do phloem cells contain?
- sieve cells/ sieve tube members
- companion cells/ albuminous cells
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