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TWO transport systems in plants: XYLEM transports water and mineral salts no need for energy as ATP made of dead cells PHLOEM transports food e.g. sucrose, amino acids using ATP made of living cells
What causesthe upwardflow withinthe xylem? Mostly,evaporationof water by the sun.
Translocation is the long-distance transport of food materials within a plant To growing regions to beGlucose produced by used as energy for growth.photosynthesis in leaf isconverted to sugars(mainly sucrose) andtranslocated to differentparts of the plant. To storage organ (fruit) to be stored mainly as sugars. To storage organ (tubers in roots) To be stored mainly as starch.
What is thefunction of root hairs?Absorb water and mineral ions.
How are root hairs adapted for absorption?1. are long and provide a large surface area2. have a thin cell wall
Question: [SEP, 2005]Plants need mineral ions which they obtain fromsoil. Explain how the uptake of mineral ions byplants, may be inhibited in waterlogged soils. (3)Ions are taken up by active transport.Active transport needs energy fromrespiration.There is not enough oxygen for roots torespire in waterlogged soils.
Transpiration stream:the flow of water from root to leaves
Transport Of Water And Mineral SaltsTransport in the Xylem There are three forces that move the water upwards in the xylem: a) Root pressure - a force that pushes water up the xylem (produced by the continuous movement of water through the root cells. b) Capillary action - a force that pushes water up the narrow xylem vessels. c) Transpirational pull - a force that pulls water up the xylem (produced by evaporation of water from the leaves).
QUESTION: SEP, 2011Describe the path taken by awater molecule from the roothair to the stomata in a leaf. (3)
Root hair absorbs water by osmosis.Water moves across the root cortex by osmosis.Water enters xylem and moves up towardsleaves, mostly due to evaporation.Water evaporates intoair spaces betweenspongy mesophyll cellsand diffuses out viastomata.
Apparatus to measure the rate of transpiration: Potometer Weight Water potometer potometer balance
Weight potometer A potted plant is well watered. A plastic bag is wrapped around the pot to prevent water loss from the soil. The apparatus is weighed at intervals and changes in weight indicate water loss.
Suggest a control for this experiment. CONTROL
To study the effect of wind speed on the rate of transpiration Which graph is for highest fan speed? C
Four factors affecting transpiration 1. Light 2. Temperature 3. Humidity 4. Wind currents
Four factors affecting transpiration 1. Light stomata open in the light and so more water is lost
Four factors affecting transpiration2. Temperature as temperature increases, evaporation increases Water molecules move faster.
3. Humidity in dry air, the plant loses more water vapour than in humid air
High humidity in air : less transpiration. WHY? A lot of water vapour in air. Not A lot of water much differencevapour inside leaf in concentration
Four factors affecting transpiration4. Wind currents moving air removes water vapour from the leaf surfaces
QUESTION: SEP, 2011Stomata allow transpiration to occur.Explain why if a plant is enclosed in atransparent bag, the rate of transpirationdecreases. (4)Air around shoot becomeshumid.Difference in concentrationof water vapour inside theleaf and in the air aroundleaf decreases.
Functions of transpiration1. The plant cools as water evaporates.2. Water is transported up the plant as water is lost from the shoot – keeps cells turgid.3. Dissolved salts move up too.
What is the picture showing? The plant lost No loss in weightweight as water as the waterevaporates in to which the air. evaporated, retur ned to flask. 2 1
QUESTION: MAY, 2012Comment on the biological significance of thefollowing statement:Transpiration may have some useful effects inplants. (4)
What is the advantage of having both shallow and deep roots?
QUESTION: MAY, 2006Olive trees (Olea europaea) are native to theMediterranean region and other hot, arid regions.Give TWO adaptations which plants living in thisregion show to reduce the rate of transpiration. (2)1. Thick waxy cuticle.2. Dense cover of short hairs on underside of leaves.3. Relatively small leaves.4. Sunken stomata.