Transport In
Angiospermophytes
Nisha Seebachan
Period 3A
January 16, 2012
Plant Support
• Terrestrial Plants support themselves by turgor pressure,
thickened cellulose, and lignified xylem because plants have
no Skelton.
• Turgor Pressure- when the vacuole will take up water pushing
against cell wall and the cell wall attempts to push back
creating a strong pressure.
• Lignified Xylem – Dead
• xylem with lignin (a carb)
• added to it. Strengthens
• the wood.
Photo Source:
http://sun.menloschool.org/~dspence/biology/chapter6/chapt6_10.html
The Root
The Uptake of Water
• Use Osmosis because the water in the soil has a lower
concentration than the cells.
• Transport Tissue: Xylem
• Water flows up xylem thus more water comes in to
maintain gradient.
• Xylem is a dead tissue with Trancheids and Xylem vessels.
• Trancheids are narrow cells allow for rapid water movement.
• Xylem Vessels larger made of columns of cells and efficient in water
transport.
From Root Hair to Xylem
• Apoplastic – Just Water and Water goes through cell wall but
doesn’t enter cell. Reaches the casparian strip which is
impermeable to water enters Symplastic pathway.
• Symplastic Pathway: Water enters
cytoplasm passes from cell to cell
through the plasmodesmata, the
connections between cells.
The Uptake of Minerals
• Occurs in 3 ways osmosis (mass flow of water in the soil
carrying these ions), active transport, and facilitated transport.
• Active Transport because mineral concentration in root higher
than content in soil. (We know this because if root does not
have ATP mineral uptake stops.)
• Phloem plays large role of active translocation of sugars
(sucrose) and amino acids from source (photosynthetic tissue
and storage organs) to sink (food storage, seeds, fruits,)
• Phloem contains sieve tube member cells and companion cells
• Phloem goes in both directions.
Transpiration
• Loss of water vapor from leaves and stems.
• Important in cooling sun drenched leaves and stems. Key to
the water cycle.
• Forces involved to allow transport: Transpiration, cohesion,
and tension.
• Adhesion- Cohesion- Tension theory of water movement –
Water diffuse out of leaf through stomata thus creating
tension in the mesophyll. Water is drawn from xylem into the
apoplast. Removal of water from the veins causes more water
to be drawn upwards.
Guard Cells and Stomata
• Plant releases gases through stomata
• Guard Cells prevent excessive water from being released but
also stops photosynthesis. When plant is at risk of drying out,
no turgor pressure, guard cells sag, thus stomata closes.
What affects Rate of Transpiration?
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Temperature
Humidity – to much water in the air, transpiration decreases
Wind – water is pulled away faster
Light –plants open stomata for photosynthesis to continue
Adaptations of Xerophytes (plants
adapted to arid climates)
• They will have smaller thicker leaves to decrease surface area
• Stomata located in pits of leaf surface thus higher humidity
near stomata
• Hair –like cells on the leaf surface trap a layer of water vapour
thus maintaining higher humidity
• Plants have thickened, wax cuticles
• Reduced number of stomata