Plants: Lecture 4 Flashcards
What are plant cell walls made of?
They are mostly composed of cellulose, a polysaccharide of glucose units.
- The cell wall is outside of the cell membrane, and stabilizes the plant.
How are the microfibrils lined up?
The microfibrils are lined up like sheets to compose the cell wall.
What are the kinds of cell wall?
There are 2 kinds:
Primary Wall: thin, in all cells
Secondary Wall: thicker, in some cells for extra strength.
Functions of cell wall?
- Determines and maintains shape
- Provides support and mechanical strength (allows tallness)
- Prevents cell membrane from bursting
- Controls rate and direction of cell growth and regulates cell volume
- Responsible for the plant architectural design
- Physical barrier to pathogens and water (suberized/waxy cells)
- Carbohydrate (starch) storage and reused in metabolic processes (seeds)
What are the three kinds of polysaccharides in the cell wall?
- Cellulose
- Hemicellulose
- Pectin
Function of Cellulose?
Polymer chain of up to 25,000 glucose molecules
- roughly 36 chains bond to make microfibril
Hemicellulose function?
They are cross-linking glycans that bond with the cellulose.
Function of pectin?
A jellylike glue in the cell wall.
What is the middle lamella?
It is the material between cells, made up of pectic substances.
Which cell wall is made first?
The primary wall is made first, and the secondary is made second, accounting for why it is on the inside of the primary wall.
What do plasmodesmata do?
They allow cytoplasm and other materials to move between cells easily
What are the three tissue systems in vascular plants?
- Dermal tissue
- Vascular tissue
- Ground tissue
What is dermal tissue?
A single layer that secretes cuticle (waxy)
What is vascular tissue?
Composed of the xylem and phloem: support and supply
- moves fluid around the plant
Ground tissue?
All tissue other than dermal and vascular: the bulk of the young plant, filling space between dermal and vascular tissues, mostly parenchyma cells, storage, photosynthesis, and support.
Types of dermal tissue?
The epidermis
Types of ground tissue?
- Parenchyma
- Collenchyma
- Sclerenchyma
Types of vascular tissues?
- Tracheids and vessel elements
- Sieve elements
What are epidermal cells and where are they located?
They are the outermost cells and made up of a single layer (sheet) covering leaves, stems and roots of non-woody plants or plant parts.
Functions of epidermal cells?
- Waterproofing the cells
- Protection from pathogens (viruses, bacteria, fungi).
- Other specialized roles (Hairs/trichomes in roots stems and leaves, Make nectar in nectary for flowers, Guard cells for gas exchange controlling opening and closing of cells during photosynthesis).
What is the cuticle, and what is it formed by?
The cuticle is formed by the epidermal cells, the outermost part being impregnated with wax. It is made of one layer of cells
- It protects against water loss, pathogens, and UV radiation.
Wax on a chamomile petal?
Chamomile flowers have a layer of wax that is arranged on the petal, making them reflect light and be white.
Pitcher plant?
Wax is arranged in one direction so that prey is caught and unable to climb back up. The lower areas have acid to kill the flies.
What are secretory trichomes?
Aromatic plants and those containing liquids because of oils in the epidermal layer.
- Mint Trichome: more than 1 cell
- Oregano: 8 cells containing aromatic oils
- Stinging nettle trichome: 1 cell containing fluid to release into victims.
- Cannabis: contains THC oils
- Marjoram: 2 small trichomes containing oil and those that hinder crawling insects.