Plants Wheeeeeeeeee.e...eeee.e..ee..e.e

Getting really really lame nowadays. LOL.

Hmmm... Getting bored now, so wanna post some info up again(:

Pressure Flow Concept is a really cool and interesting concept that I would really like to share with you all. It is somehow linked to Translocation which is the transport of substances like sugars manufactured to the other parts of the plants.
1) Sugars manufactured form the source will move out to the phloem (sieve tube)
2) Water will also move out to the phloem via osmosis
3) Water present will cause a pressure gradient for sugars to move through the sieve tubes.
4) In areas where sugars are used up or removed for storage, sugars will move out of phloem
via diffusion or active transport.
5) Water will then move out of phloem and get conducted back to xylem.

(Therefore, aphids will Ooozzzze out a fluid which is actually sugars)

Hmmm.... Transpiration is a process whereby water is loss through the stomata of the leaves
Transpiration pull is resulted from a few procedures:
1) Water from the mesophyll moves out via osmosis and forms a thin film of moisture
2) Thin film will then evaporate to the intercellular spaces and leave the plant via stomata
3) Cells that loses water will have decrease in water potential and so will get water from
deeper cells.
4) Deeper cells get water from xylem directly and so will form a suction force to pull water
upwards, causing transpiration pull

Water moves up xylem in 3 ways:
1) Root Pressure:
Difference in water potential between soil and roots will cause water to move from soil to roots and this pressure created will force water from root hair cell up to xylem vessel
2) Capillary Action:
Cohesion forces between water molecules and adhesive forces between water and xylem vessels will allow water to be conducted upwards without breakage.
3) Transpiration Pull:
Due to cells that draw water directly from xylem vessels, allowing water to move against gravity.

Transpiration rate affected by a few factors:
1) Wind Movement: Higher amount of wind present will lead to water vapour to be blown away and lesser humidity allows more water to move out of plant.
2) Humidity: The more humid, the lesser transpiration as high water potential in surrounding will hinder water out of the leaves.
3) Temperature: Higher temp. will allow water vapour to be evaporated off quickly and so allowing more water to move out due to less humidity
4) Light Intensity: More light will cause stomata to open as photosynthesis occurs and so more water vapour will move out of plant.
5) Water potential: More water supplied to plant, will allow plants to lose more water without wilting.

Wilting occurs when more water loss than uptake and will cause plant cells to become flaccid and photosynthesis cannot take place.
1) Leaves fold up to reduce surface area for sunlight
2) Guard cells become flaccid and closes stomata

Transpiration importance:
1) Allow biochemical reactions to take place.
2) Give plant cells turgor pressure to keep upright
3) A very good solvent

Transpiration's bad:
Causes wilting

Xylem- Conducts water and to provide plants with mechanical support with its lignified wall
Phloem- Conducts food substances and ions

How do plants reduce transpiration:
1) Having a thick boundary layer where water have to move through a long way before it can move out
2) Having a cuticle layer
3) Having hair: Reabsorb water back to plant and prevent excessive loss of water

Joelle (: