1 / 30

Plant Responses to Temperature

Plant Responses to Temperature. Chapter 10; p322. Plants surviving heat. Plants and Energy. Plants receive a lot of energy from the sun, but only use about 1% of it. They generally maintain a constant internal temperature and regulate their temperature through: Radiation Transpiration

melba
Download Presentation

Plant Responses to Temperature

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Plant Responses to Temperature Chapter 10; p322

  2. Plants surviving heat

  3. Plants and Energy • Plants receive a lot of energy from the sun, but only use about 1% of it. • They generally maintain a constant internal temperature and regulate their temperature through: • Radiation • Transpiration • Convection • Leaf shape • Heat shock proteins • Leaf orientation

  4. Heat gain and loss in plants

  5. Transpiration • Transpiration – Evaporation of water from leaves. • Most is lost through stomata, some through the cuticle. • Cuticle – waterproof outer layer of leaf. • Too much water loss can cause loss of turgidity (in cells) and then wilting.

  6. Convection • Convection air currents carry heat away that is lost through radiation and evaporative cooling.

  7. Leaf shape • Leaves lose most heat where the two surfaces of the leave come together at the edge. • Some leaves have reduced edge to surface area based on their shape. • Leaf A has a large edge to surface area and therefore will lose heat faster.

  8. Heat-shock proteins • Some temperate plants produce special heat-shockproteins at around 400 to protect enzymes from denaturing (breaking down).

  9. Leaf Orientation • Some plants and trees (e.g. Eucalypts) orientate their leaves so that minimise surface area facing the sun during the hottest part of the day. • Leaf (b) has least exposure to the sun

  10. Specialised structures • Some trees have specialised structures to store water. • Pictured: Boab trees of northern/central Australia.

  11. Leaf fall • Some plants and trees drop leaves  reduces surfaces area from which heat is absorbed.

  12. Plants surviving cold Page 324

  13. Surviving the cold • Some animals produce an ‘anti-freeze’ – plants do not. • In extreme cold, ice forms in the spaces between cells.  Water moves out of the cell into these spaces making the crystal larger.  Ions in the cytosol (fluid filled space in a plant cell) become more concentrated and act as an ‘anti-freeze’.

  14. Surviving the cold Ice forms between cells but does not puncture the cell.

  15. Plants and water Balance Page 330

  16. The importance of water • Water makes up to 90-95% of the living tissue of plants. • Without it, they wilt and then die.

  17. Quick overview of transport systems in plants. • Water is drawn up from the roots and transported into all parts of the plant in a transport system called the xylem.

  18. Xylem • Xylem: tubular pathways in the roots, stems and leaves. • Xylem – distributes water and minerals in the plant in one direction – from roots to leaves.

  19. Phloem • Phloem: transports sugars in either direction  requires energy.

  20. Stomata and transpiration • When mesophyll cells contain sufficient water  stomata open (so gases can be exchanged with the environment)  water is lost through transpiration • Water is replaced in mesophyll cells by water from the xyelm.  roots draw more water from the soil to replace water lost from xylem. • Mesophyll cells – photosynthetic cells found in leaves.

  21. Movement of water • Water evaporating from leaves drives the uptake of water from the roots through osmosis. • Osmosis – diffusion of water from a high concentration to lower concentration. • More technically: Diffusion of water from a low solute concentration to a high solute concentration.

  22. A trade-off • Plants must open stomata to take in carbon dioxide for photosynthesis and release oxygen. • When they do, water vapour is lost.

  23. Factors affecting transpiration • Humidity – lower humidity  greater evaporation and water loss. • Winds – higher winds  greater water loss through evaporation. • Air temperature – higher temperature  greater water loss.

  24. Humidity and water loss In scenario (a) there is less water vapour in the air (low humidity). Therefore more water will be drawn out of the leaf through stomata.

  25. Plant adaptations to reduce water loss p332

  26. Xerophytes • Xerophytes – ‘lovers of dryness’ • Plants adapted to dry, hot conditions.

  27. Sunken stomata • Stomata in folds or sunken trap a layer of moist air  reduces water loss through transpiration

  28. Rolled up leaves • Stomata on one side of leaf. • Leaf curls up protecting stomata from hot, dry air.  Reduces water loss through evaporation

  29. Succulents • E.g. Aloe Vera, Cacti • Few stomata • Efficient root system

  30. No leaves - Phyllodes • E.g. Some adult Acacia’s • Phyllodes – flattened petioles (leaf stem) • Have no stomata  reduces water loss through transpiration

More Related