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:

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? 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