9. Plant Biology Flashcards
9.1 Why are stomata neccasary?
The waxy cuticle of the plant has low permeability
9.1 What are guard cells?
Cells around stomata that open and close it, swollen with water= open, contracted = less water
9.1 Draw a xylem structure
9.1 What is in the xylem walls to thicken it?
Lignin
9.1 Properties of water that are important for plants:
Adhesion: attracted to hydrophillic xylem walls
Cohesion: sticks to one another (chain)
9.1 Describe the process of evaporation in the xyelm.
Water evaporates from the leaf surface and adhesion draws water from the nearest source: xylem. This lowers the water pressure and water is drawn up.
9.1 What does the xylem move?
Water and ions
9.1 What are halophytes?
Plants adapted to salty conditions
-cellular sequesterations within cell walls or vacuoles
tissue partitioning
root level exclusion
- salt excretion
9.1 What are xerophytes?
Plants that tolerate dry conditions
-rolled leaves
-reduced leaves
-thick cuticle
-stomata in pit
-low growth
9.1 How is water replaced in the xylem
Water is drawn into epidermis root hair cells. From there it either takes the symplast (through cytoplasm) or apoplast pathway (cell wall). The apoplast pathway stops at the casparian strip at the endodermis cell. From there it passes through plasmodesma into the pericyle then the xylem.
9.2 What is the process of the phloem?
Translocation
9.2 What is the structure of the pholem?
Made up of living sieve tube cells seperated by sieve plates, accompind by companion cells
9.2 Draw a phloem
9.2 What is translocation
The movement of organic compounds from sources to sinks
9.2 Examples of sources
Photosynthetic tissue
Unloading storage
9.2 Examples of sinks
Roots
Growing plant
9.2 Osmotic pressure at sinks vs sources.
At sources, high concentrations of solute draw in lots of water = high pressure
At sinks, solutes are withdrawn so water is low pressure, goes back to xylem
9.2 What carbohydrate is in sap?
Sucrose, not easily metabolized: good transport form
9.2 How does phloem loading for sucrose work (2 methods)?
Symplast route: Sugar producting cell and companion cell are connected with plasmodesmata (simple diffusion)
Apoplast: There is a space called the apoplast between the two cells. Simple diffusion from producer into space. From there a H+ pump pushes H+ into the apoplast and a Sucrose-H+ cotransport pump puts them into the companion cell (following H+ gradient)
9.2 How to identify phloem vs xylem?
Xylem are always more internal
In roots xylem may form an x, in stem they may be separated by cambian strip
9.2 Properties of sieve cells
1) No nucleus
2) Limited cytoplasm
3) Companion cells
9.3 Specifics of plant growth
Most plant experience indeterminate growth
- Have totipotent cells capable of any cell type
9.3 Draw and label a seed
9.3 What is a meristem?
Plant tissue that remains embryonic (undifferentiatted)
Apical:
- length growth
-tips of roots and stems
Lateral
- wideth
- in between xylem/phloem
- bark
9.3 What are cytokinins?
Key plant growth hormones, promote cell division (w/auxin)
- promote lateral bud formation
- root apical meristem
9.3 What affects rate and direction of growth?
Phototropism and gravitropism
9.3 What is auxin?
A plant growth hormone. It activates proton pumps in cell walls and the resulting decrease in pH causes cellulose to expand, influx of water causes cell to stretch
PIN3 protiens transport auxins
9.3 Resulting auxin growth
Phototropism: Auxins are transported to dark side, plant tilts towards light (stimulate elongation)
Gravitopism: Auxins on bottom inhibit growth
9.4 Process to begin flowering.
OG plant = vegetative structures
The change to reproductive involves meristem at shoot apical
9.4 Light response hormone
Phytodrome switches between Pr ( inactive ) and Pfr (active)
Red or white light changes it into an active form, in darkness it slowly returns to the more stable Pr form.
9.4 Long day plants vs short day plants
Long day plants (early summer): Large amounts of Pfr bind to receptors to transcript flowering gene (receptors promote)
Short-day plants (fall): Receptors inhibit gene, little Pfr = receptor isn’t active
9.4 How does fertilization work?
The pollen grain lands on the surface of the stigma. A pollen tube is produced to connect the two and the male gamete travel down it.
9.4 What is needed for seed germination?
O2: Respiration
Water: Metabolically activate
Temp: Activates enzymes
pH: suitable
9.4 Label the flower of a plant
9.4 What are the steps of reproduction
1) pollination
2) fertilization
3) seed dispersal
9.4 Monocots vs dicots angiospermophyta
Monocots
- one cotyledon (Seed)
- upper and lower epidermis stomata
- fiberous roots
- scattered vascular
- parallel veins
- flowers in multiples of 3
Dicots
- two cotyledon
- tap roots
- ringed vascular
- net-like leaves
- 4 or 5 flower petals
