Plant Biology Flashcards
Define Transpiration
It is the loss of water vapour from the stems and leaves of plants by evaporation.
Define evaporation in terms of plant bio
It is the loss of water when it is converted into vapour and diffused out of the stomata.
Define Transpiration steam
The flow of water through the xylem from the roots to leaves, against gravity.
Where does the light dependent reaction of photosynthesis take place ?
In the thylakoid inter-membrane space.
Factors affecting transpiration
Humidity
Temperature
Light intensity
Wind
Define Xylem
The vascular tissue in plants which transports water upwards in one direction from roots to leaves. It is composed of lignin and dead cells.
Define Vessel Elements
The end walls in xylem become fused to form a continuous tube which allows for faster rate of water transfer.
Define Casparian Strip
A structure formed in the extra-cellular matrix of cells at the cross wall between adjacent endodermal cells. It functions as a barrier to ions forcing them to pass through the selectively permeable plasma membrane into the cytoplasm rather than move along cell wall.
Define Symplastic pathway
Water moves continuously through the cytoplasm of cells ( connected via plasmodesmata).
Define Apoplastic pathway
Water cannot cross the casparian strip and is transferred to the cytoplasm of the endodermis.
Define Tracheids
Tapered cells that exchange water solely via pits, they have a slower rate of water transfer compared to the xylem.
Define Zone of division
It is where new undifferentiated (unspecialised) cells are formed. These cells are called merstematics cells.
Define Zone of elongation
It is where cells enlarge in size corresponds to G1 phase in interphase.
Define Zone of maturation
It is where cells become specialised and become a functional part of the plant.
Define Apical Meristem
Cells found at the top and bottom of the plant, responsible for the plants primary growth (stems extends vertically and roots extend downwards).
Define Lateral Meristem
Cells found in roots and stems of plant, it is responsible for the secondary growth (grow larger in diameter). It consists of 2 types Vascular cambium and Cork Cambium.
Define Vascular Cambium
Produces more vascular bundles which ate major part of wood.
Define Cork Cambium
Occurs within the bark and produces the cork cells (Protective water-resistance cells).
What does sap consist of?
- Sugar
- Amino acids
- Hormones
Define Girdling
Slow killing of a tree by removing a ring of bark and the phloem.
Define Translocation
The movement of organic compounds (e.g. sugars, amino acids) from sources to sinks via the phloem.
How can translocation be measured?
- Aphids (insect style)
- Radioactive carbon dioxide
(radioactive carbon becomes a part of the sugar and can be tracked).
Define Dermal tissue
The outer covering that protects against the environment, potential pathogens and water loss.
Define ground tissue
Thin-walled cells that function relates to storage, photosynthesis, support and secretion.
