Plant transpiration


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Plant transpiration

  1. 1. Plant Transpiration
  2. 2. 1. Importance of Transpiration2. Process of Transpiration3. Role of Stomata in the Process4. Factors Affecting Transpiration5. Xerophytes
  3. 3. 1.TranspirationTranspiration is the loss of water by evaporation in terrestrial plants. It then enters the atmosphere and becomes a part of the water cycle.
  4. 4. The Water Cycle
  5. 5. The Importance of Transpiration The process of transpiration is a very important procedure for plants. It creates a negative pressure gradient that helps draw water and minerals up through the plant from its roots. Helps to keep the plant cool on hot weather - a method of evaporative cooling. It supports photosynthesis and encourages the exchange of gases, helping maintain levels of CO2 and O2 in the atmosphere.It also- plays an significant role in the water cycle and releases approx 10% of water back into the environment. produces 200 to 1,000 lb (90–450 kg) of water for each pound of solid material produced by the plant. Creates water vapor that forms into fog and clouds.
  6. 6. 2.The Process of Transpiration  Water enters into the root hair cells by osmosis.  The root hair cell is hypertonic (higher osmotic pressure) than the surrounding soil water and means that it has a lower water molecule concentration.  Water moves from cell to cell through the root cortex by osmosis along a concentration gradient; this means that each cell is hypertonic to the one before it.  In the centre of the root the water enters the xylem vessels.  Water may move by diffusion through the cell walls and intercellular spaces.
  7. 7. 3. Role of Stomata  The pores in the stoma play an essential role in the process of transpiration.  The two guard cells control the opening and closing of the pore .  The rate is dependant upon the opening time and the number of stomata present.  In sunlight the stomates are open and the sun provides the energy that keeps moving all of the way to the stomata where water changes form from a liquid to a vapor. At night, the cells remain closed.  The stomata release water in the  atmosphere, which is then broken down into oxygen and hydrogen. In return, the atmosphere gives carbon-dioxide to the plant to complete its process of photosynthesis. The number of stomata varies in from plant to plant. In xerophytes the number of stomata will be less as compared to the other plants. This reduces the water loss and helps the plant to survive in very dry conditions. The plant may also close its leaves if there is excesive sunlight, to save the water from transpiration. All these activities form a part of plant biology.
  8. 8. Transpiration  Stomata also allow controlled release of water molecules into the atmosphere. Although the plant cannot afford to lose too much water to the environment, the plant must have a way to carry water and minerals from the roots, up the stem, and out to the leaves. Transpiration is the loss of water through the stomata. By allowing some water molecules to escape the leaves through the stomata,  Plants have a balancing act to follow - they have to let in enough carbon dioxide for photosynthesis and enough oxygen for cellular respiration, without losing too much water. So, stomata open and close in response to environmental cues. Temperature, humidity, the concentration of carbon dioxide, and even the presence or absence of light affects the turgor of the guard cells, which controls the opening and closing of the stomata.
  9. 9. 6.Factors affectingTranspiration Factors effecting transpiration rate The opening and closing of the stomata is controlled by the guard cells. In light, guard cells take up water by osmosis and become turgid. Because their inner walls are rigid they are pulled apart, opening the pore. In darkness water is lost and the inner walls move together closing the pore. Because of this, the transpiration rate is increased by an increase in light intensity. The rate of transpiration can be affected by several factors: The opening and closing of the stomata by the guard cells (stomatal rhythm) - In light, guard cells take up water by osmosis and become turgid. Because their inner walls are rigid they are pulled apart, opening the pore. In darkness water is lost and the inner walls move together closing the pore. Because of this, the transpiration rate is increased by an increase in light intensity. Plants which live in extreme environments have adaptations to control their transpiration rate.
  10. 10. 6. xerophytes Desert plants have a real challenge to  Water is transported from the roots to the minimize water loss, since their environment leaves through a vein structure known as the is so hot and dry. Xylem. Water and minerals are sucked up Xerophytes live in deserts where water is as water evaporates from the leaves of scarce and evaporation is rapid, or in windy plants in a process known as Transpiration. habitats where evaporation can also be  The process of transpiration- Transpiration is rapid. Their typical features are: a process of emission of water from the plant deep roots to reach water far underground with the help of small openings known as shallow spreading roots to collect occasional stomata. Stomata are small openings or rainfall pores which are present in the aerial part of the plants like in the leaves reduced to spines with minimum leaves, stem, flowers, etc. But leaves surface area for transpiration constitute the major portion of stomata. reduced number of stomata to reduce transpiration rate rolled leaves, leaf hairs and stomata sunk in pits to trap moist air, increasing humidity and slowing diffusion of water vapour from the stomata waxy leaf cuticle which is impermeable to water (preventing evaporation) stomata opening at night and closed at midday when evaporation rate would be highest (reversed stomatal rhythm). storage of water in succulent tissues
  11. 11. 5. Factors AffectingTranspiration Factors affecting the rate of transpiration. High temperature may result in the opening of stomata and hence, increases the transpiration. In the normal procedure, plant gets water from the soil. If plant does not get water from the soil, the stomata remains closed. The rate of humidity is inversely proportional to the rate of transpiration. That means when humidity increases, transpiration decreases. Light increases the temperature which in turn, increases transpiration. Transpiration increases with the wind but high winds result in the closing of stomata which reduces transpiration. Leaf structure, type of stomata, root and shoot ratio, etc., may also affect the rate of transpiration.
  12. 12. Bibliography ogy/genetics_adaptation/maintaining_water_balance_rev4 .shtml ration.html mats/transpiration web/10000/science/10000-6580.html ew.ashx