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TOPIC 9 PLANT BIOLOGY - Coggle Diagram

- - - - displaced minerals diffuse into root (indirect active transport)
      - water follows mineral ions into the root via osmosis
  - - - pressure is high in root (water in) and low in leaf (water out)
      - the pressure differential results in the mass flow of water
    - - cohesion (water molecules stick together by H-bonding)
      - adhesion (water molecules adhere to the xylem wall)
  - - - transpiration rate is regulated by the stomatal guard cells
      - guard cells occlude the stomatal opening when flaccid
  - - - reduced leaves (lowers evaporative surface area)
      - thick, waxy cuticles (reduces water loss from leaves)
      - stomata in pits with hairs (traps vapor = less evaporation)
      - CAM physiology (only opens stomata at night)
    - - cellular sequestration (salt is stored within the vacuoles)
      - tissue partitioning (abscission of leaves containing salt)
      - salt excretion (salt is actively removal from the plant)
      - root level exclusion (roots avoid salt uptake)
  - - - capillary tubing (water moves along tubing via surface tension)
      - filter paper (absorbs water due to adhesive properties)
      - porous pots (semi-permeable containers can model osmosis)
    - - potometers measure movement of air bubble /meniscus
      - more movement represents increased transpiration rate
- - - - they have specific regions of growth or development and allow for regrowth and vegetative propagation
    - - occurs in shoots and roots and is responsible for primary growth (i.e. lengthening) and leaf development
    - - occurs at the cambium and is responsible for secondary growth (i.e. widening) and the production of bark
  - - - auxin efflux pumps can set up concentration gradients of auxin in plant tissues to allow for differentiated growth rates
    - - auxin influences cell growth rates by changing the pattern of gene expression within the plant tissue
  - - - Axillary buds have the potential to form new shoots
    - - this condition is known as apical dominance
  - - - growing shoots are divided and transferred to soil to form new plants
      - tissue sample (explant) is grown in agar and treated with growth hormones
  - - - in plant shoots, auxin promotes cell elongation
      - in plant roots, auxin inhibits cell elongation
- - - - upper layer of tightly packed cells that are rich in chloroplasts (more light absorption)
    - - lower layer of cells interspersed by space and located near the stomata (more gas exchange)
  - - - vascular bundles are radially arranged within a big stele in monocots, but are centrally arranged within a small stele in dicots
    - - vascular bundles are scattered haphazardly in monocots, but form a ring around a circular cambium in dicots
- - - - pollination – The transfer of pollen from the anther to the stigma (usually occurs between different plants)
      - fertilisation – The fusion of the male gamete nuclei (in pollen) with the female gamete nuclei (in ovule)
      - seed dispersal – The fertilised ovule (seed) moves away from the parent plant to reduce the competition for growth
    - - the plant gains a mechanism of pollen transfer, while the animal gains a source of nutrition (plant nectar)
  - - - oxygen (to produce ATP via aerobic respiration)
      - water (to metabolically activate the cells)
      - suitable temperature and pH (for enzyme activity)
  - - - the response of a plant to the length of day or night
    - - inactive red form (Pr) absorbs red light (to become Pfr)
      - active far red form (Pfr) absorbs far red light (forms Pr)
    - - the active far red form is predominant during the day
      - reverts to mainly the inactive red form at night
    - - flowering requires a set length of uninterrupted darkness
    - - Pfr activates flowering in long-day plants
      - flowering induced when night length is short (more Pfr)
    - - Pfr inhibits flowering in short day plants
      - flowering induced when night length is long (less Pfr)
- - - - source: photosynthetic tissues (e.g. leaves)
      - sink: storage organs (e.g. fruits, seeds, roots)
    - - organic molecules are loaded and unloaded into the
        phloem by companion cells at the source and sink
    - - water is drawn into the phloem from the xylem (osmosis)
    - - mass flow drives sap along the phloem (source to sink)
    - - loss of water lowers the hydrostatic pressure at the sink,
        maintaining the pressure gradient (and mass flow)
  - - - composed of a perforated inner layer of dead cells that
        are fused into a continuous tube (vessel element)
      - the cell walls have thickened cellulose are reinforced
        with lignin (spiral or annular arrangement)
    - - composed of living cells connected by porous plates at
        their transverse ends (sieve elements)
      - are supported by companion cells that are connected
        via plasmodesmata to mediate material exchange
    - - translocation rates can be measured using aphid stylets
        
        aphids are insects that feed on the sap in phloem via a
        protruding mouthpiece called a stylet
        
        if the stylet is severed, the sap will continue to flow
        from the plant and can be collected and measured
        
        plants exposed to radioactive carbon dioxide will
        produce radioactively labelled sugars within the phloem
        
        the rate of translocation can be identified by the time
        taken for radioisotopes to be detected along the phloem