Plant Biology Flashcards
What plant consists of?
- stem
- leaf
- root
What is the function of stem?
- transports organic materials, ions, and water between the roots and leaves
- storages nutrients.
Structure of the stem
- At the top of the stem there is a terminal growing point
- In the axil of each leaf there is an axillary bud (new cells are produced there)
What does leaf consists of and what is its function?
Consists of a leaf blade and it connected to the stem by the leaf stalk
- it is the organ specialized for photosynthesis
What is the function of root?
- anchoring the plant
- site of absorption of water and ions from the soil
What does the stem consists of?
- vascular bundle (xylem- facing the stem inwards and phloem- facing the stem outwards)
- cambium
- cortex
- epidermis
What is xylem?
Xylem is a dead tissue that has no cytoplasm.
Function of xylem
Transports nutrients and water from roots to stem and leaves.
Structure of xylem
- vessel elements that allow for faster movement of water
- tracheid that allows for exchange of water via pits and leads to slower rate of water movement
- lignin thickening in its walls
What is the transport of water and minerals via the xylem called?
Bulk flow transport
Explain bulk flow via xylem
Water and minerals from the soil enter the plant through the epidermis of roots and pass into the vascular bundle. The water and dissolved minerals in the xylem are transported by bulk flow to the veins of the leaves.
What is phloem?
Living tissue that is responsible for active translocation of sucrose and amino acid from source to sink.
Difference between source and sink
- source is a location in a plant where a resource is taken up
- sink is a location where a resource is used.
What is the structure of phloem?
- sieve tubes
- companion cells
- sieve plates
Sieve tubes
they do not have nucleus, mitochondrion, ribosomes and vacuoles. This reduction enables for nutrients to pass more easily through the cell
Sieve plates
They facilitate the flow of fluid from the cell to the sieve tube.
Companion cells
Located alongside each sieve tube element. They help to load sugars into the sieve tube elements and transport sugars to other parts of the plant.
What is the external structure of leaves?
- leaf blade - flattened part of the leaf
- petiole - leaf stalk
- stipules - base of the leaf
What is the internal structure of the leaf?
- upper epidermis
- palisade mesophyll cells
- spongy mesophyll cells
- xylem and phloem
- lower epidermis
- stomata
- guard cells
The function of upper and lower epidermis
protection of the leaf
function of palisade mesophyll cells
contain chloroplast for photosynthesis
function of spongy mesophyll cells
facilitates the movement of oxygen
guard cells and stomata function
- guard cells - close stomata
- stomata - opening in leaves that allow for gas exchange in leaf
2 main transports of water to xylem
- mass flow - apoplastic pathway
- diffusion - symplastic pathway
Apoplastic pathway (mass flow)
This involves the movement of water and solutes through the non-living spaces outside the plasma membranes of plant cells -> to xylem
Symplastic pathway (diffusion)
This involves the movement of water and solutes through the interconnected cytoplasm of plant cells via plasmodesmata. Substances can pass from cell to cell without crossing cell membranes directly -> to xylem
Plasmodesmata - meaning
channels that connect adjacent cells
Explain osmosis process
The transport of water from vacuole to vacuole of the cells driven by the gradient in osmotic pressure.
Casparian strip
Belt made out of waxy material that does not allow the water and dissolved materials cannot cross the endodermis.
Cohesion tension theory
Water is pulled upward in plants due to the cohesive attraction between water molecules and the tension created by water loss through transpiration in leaves. This creates a continuous column of water in the xylem, facilitating upward movement from roots to leaves.