Topic 5: Anatomy of dicotyledonous plants Flashcards
Explain the epidermis in a root structure.
Closely packed cells
Protect cells from injury
No cuticle / waxy layer which allows water to move into the root
Explain the root hair cells in a root structure.
Extensions of epidermal cell
Found near the root tip
Helps increase surface area for more absorbtion
Explain the cortex in a root structure and what the function of it is?
Tissue beneath epidermis
Many layers of parenchyma cells
Function:
- Transport water to xylem
- Store starch
What does the endodermis do in a root structure?
Helps channel water into xylem
A single layer of cells around the center of vascular tissue
Casparian strip - a waxy waterproof band in the cell walls of epidermal cell
What is the function of the pericycle in a root structure?
Forms lateral roots
Single layer of parenchyma cells to inside of endodermis
Explain what the vascular tissue of a root structure is.
Consists of xylem, phloem and cambium
In the center of the root to inside of pericycle
Cambium cell divide by mitosis to produce xylem and phloem cells
What is the function of the stem of a plant?
Holds the plant upright
Transports substances between root and leaves
Phloem carries food from leaves to rest of plant
Xylem carries water from roots up stem to rest of plant
Explain the epidermis in a stem structure.
In young green plants:
- Single layer
- Closely packed
- Hairs may be present
- Covered with waxy layer to reduce water loss
In woody stem:
- Made up of a number of layers called bark
Explain the structure and function of the cortex in a stem structure.
Parenchyma cells with thin walls
Provide structure when turgid
Collenchyma cells with thickened walls
Provide structure and support
What are turgid cells?
Vacuole full of water pushes against cell wall
Give structure and support to cell
Explain what the vascular tissue of a stem structure is.
Arranged in a ring in dicot stems
Xylem on inner side
Phloem of outer side
Cambium separates xylem and phloem
Schlerenchyma tissue surrounds vascular tissue and gives support
What is the pith?
Made of parenchyma cells
Stores starch
Center of stem
What is the vascular cambium in a stem structure?
Separates xylem and phloem
Produce new xylem and phloem cells by cell division
What is the cambium ring?
Formed by vascular cambium, visible with secondary thickening
What is transpiration?
Loss of water through the stomata in form of vapour, creates pull from plant
Which factors affect transpiration?
High temperature
High humidity
Lots of wind
High light intensity
What are the internal structure factors of transpiration?
- Leaf arrangement (open = greater transpiration)
- Size and shape of leaf (bigger surface area = greater transpiration)
- Stomata (few stomata = lower transpiration)
- Thickened cuticle (reduces rate of transpiration)
- Presence of hair ( traps water vapour = lower transpiration)
What is a potometer?
An apparatus used to measure rate of transpiration
What is plasmolysis?
Water continues to be lost
Vacuoles shrink because of water loss
Plant cells loses too much water, cell membrane pulls away from inside of cell wall
can be reversed = deplasmolysis
Permanent wilting may result in death
What is guttation?
Release of water in the form of water droplets through the stomata, happens in very humid places
Explain the uptake of
water and
minerals
from the
soil.
Absorption of water into the root
Water enters the plant via root hairs by osmosis
Root hairs thin and long to reach between soil particles.
Come into contact with more water
What is water potential?
The ability of the plant to lose or gain water
What is the properties of a liquid with a high water potential and give an example?
Has few dissolved substances
Is more likely to lose water
E.g. Soil water
What is the properties of a liquid with a high water potential and give an example?
Has many dissolved substances
Is more likely to gain water
E.g. vacuole
How will water move?
Water will always move from an area of
high water potential to an area of low
water potential
Explain the structure of a root hair.
Large surface area
Very thin between soil particles
Large vacuole with low water potential
What are the three pathways through
which water moves along
the cortex?
Apoplastic = Cell wall
Symplastic = Cytoplasm
Transcellular = Vacuolar
What cells does water move through the cortex?
Parenchyma cells
Explain the cell wall pathway.
Quickest way
As water travels reaches the endodermis
Casparian strips forces water through cell membrane into cytoplasm - to direct water towards xylem
Explain the cytoplasm pathway.
Through plasmodesmata (small strands of cytoplasm
in cell walls which connect
cytoplasm of adjoining cells).
Explain the vacuolar pathway.
Only a small amount moves this way.
What is at the xylem vessels?
Water from all 3 pathways enters through pits in xylem walls, xylem transports water up the stem to the leaves
What is the structure of the xylem in the transportation of water and minerals?
Continuous
Uninterrupted flow of water
Vessels are empty
Small diameter which increases diameter
Lignified which gives strength
Hollow
What do the pits allow in the xylem?
Sideward movement of water
What are the forces assisting upward movement of water?
Transpirational pull
Capillarity
Root pressure
What is transpirational pull?
Evaporation and loss of
water from the surface of the leaf through
stomata, the suction force causing the upward movement of water
What is capillarity?
The ability of water molecules to rise up a very narrow tube by sticking to each other.
Xylem – narrow tubes, smaller the diameter of the tube the higher the
liquid rises
What is root pressure?
Pushing from the bottom
Water will move from a high concentration to a low concerntration
Explain the translocation of food.
Movement of substances
From the leaves to the rest of the plant
Inside sieve tubes of phloem
Moves downward
Energy is required
Companion cells help in the function
