Transpiration

hydrological and biological perspective

1. Transpiration

2. The W ater C ycle

3. Definitions The physiological process by which the excess water is lost from the living tissues of plants in the form of vapor is called transpiration. Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers. Transpiration is the process by which water vapour leaves the living plants body and enters the atmosphere. (Michel,1978)

4. According to recent studies it has be revealed that about 10 % of the moisture found in the atmosphere is released by plants through transpiration. The remaining 90% is mainly supplied by evaporation from, ocean, seas, lakes, rivers, streams etc. During dry periods , transpiration increase the loss of water in the upper layer of soil, which effect vegetation, horticultural and agronomic field crops. Plant transpiration is pretty much an invisible process. Transpiration is the evaporation of water from plants and trees. Approximately 90% of all water taken up by a plant is lost to transpiration. Characteristics

5. Transpiration is the final step in a continuous water pathway that starts from the soil, into plant roots and ends as it passes into the atmosphere. 98% of a plants energy is used in the work of transpiration Transpiration rates are highest in leaves. Transpiration is an elegant, sustainable natural design that performs its vital functions without electricity, without fossil fuels and without moving parts Many xeric plants have small leaves, silvery reflective leaves, hairy leaves and/or produce essential oils which are all strategies to reduce transpiration by reducing evaporation. Characteristics

6. Transpiration is a very useful procedure for plants- It creates 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 evaporating cooling. Supports photosynthesis and encourages the exchange of gases, helping maintain levels of CO 2 and O 2 in the atmosphere. Importance of transpiration

7. It also plays an significant part in Global Hydrological Cycle- Releases approx 10% of water back in to the environment . Produces 90-450 kg of water for each pound of solid material produced by plants. Creates water vapor that forms into fog and clouds. Transpiration is also the reason why there is higher humidity in places with lots of vegetation cover Transpiration through plant stomata is the main pathway for water entering the atmosphere over land. To a water resources person , transpiration is considered a loss to the watershed. If plants could somehow use less water, the amount saved would remain on the ground to increase recharge importance

8. On the basis of the passages through which plants give out water in the form of vapor transpiration is of three types: Types of transpiration

9. Stomatal transpiration: Transpiration that occurs through stomata called stomatal transpiration. This type of transpiration only occurs in its presence of sunlight (in daytime). Because stomata open in the present of sunlight and close in the darkness. In this method plants give out 80-90% water in the form of vapor. Types of transpiration

10. Types of transpiration

11. Cuticular transpiration: Transpiration that occurs through the cuticle or cracks of thin cuticle layer of leaves and stems is said to be cuticular transpiration. This is a day-night process. In this process, 5-10% water is given out in the form of vapor. Types of transpiration

12. Lenticular transpiration: Sometimes transpiration occurs through lenticels, the small opening in the corky tissue covering stems and twigs , and this type of transpiration is said to be the lenticular transpiration. In this process, only 0.1% water is given off of the forms of vapor. Types of transpiration

13. Types of transpiration

14. Vs. Transpiration vs Evaporation

15. Transpiration vs Evaporation

16. Transpiration vs Evaporation

17. Water is passively transported into the roots and then into the xylem. The forces of cohesion and adhesion cause the water molecules to form a column in the xylem. Water moves from the xylem into the mesophyll cells, evaporates from their surfaces and leaves the plant by diffusion through the stomata. Mechanism of transpiration

18. Mechanism of transpiration It involves three basic steps Absorption at the roots. Capillary action in the xylem vessels. Evaporation at the leaf.

19. Roots absorb water from the soil through osmosis. Water travels from high concentration area to low concentration area via a semi-permeable membrane called osmosis. Cell water concentration < soil water concentration. Absorption

20. why not soil molecules enter? Active Transport Passive Transport Requires cellular energy. Does not require cellular energy. It circulates from lower concentrated areas  to the higher concentrated areas It circulates from the higher concentrated areas to the lower concentrated areas Absorption

21. Absorption

22. How does the water goes up against gravity?

23. Turgor pressure

24.  The rate of loss of water from the plant is greater than the absorption of water in the plant Wilting

25. Transpiration Pull

26. Adhesion occurs when water forms hydrogen bonds with xylem cell walls. Cohesion occurs when water molecules hydrogen bond with each other. Cohesion between water molecules creates a “water chain” effect. Capillary Action

27. Evaporation

28. Molecules move from higher concentration to lower concentration, this is called diffusion. Internal vapour >atmospheric vapour . Evaporation

29. Total Process

30. Water potential quantifies the tendency of free (not bound to solutes) water to move from one area to another due to osmosis, gravity, mechanical pressure, or matrix effects such as surface tension. Water potential

31. Distilled water  P = 0 S =  = 0 MPa Water potential

32. Water potential

33. Water potential

34. Lack of water in soil Reduce the number of leaves Turn the leaves into spine Leaf---spine stomata—less number of stomata—reduce transpiration Example: cactus Adaptation & Distribution Xerophyte plants

35. Mountain Plants Atmospheric pressure decrease Evaporation increase Transpiration rate increase OAK:40000 gallon/year Adaptation & Distribution

36. Cold climate and Deciduous Shedding of leaves Reduce transpiration Deciduous tress shed twice a year Adaptation & Distribution

37. Cold climate and Evergreen trees Reduce surface area of leaves Decrease surface area into needle like structure Reduce number of stomata Reduce transpiration example-pine Adaptation & Distribution

38. Equatorial E vergeen Bigger leaves,big surface,lot of stomata Thik waxy layer known as cuticle Cuticle cover the stomatal opening in epidermis Prevent excessive loss o f water Help to limited amount of transpiration Ex-banana leaf Adaptation & Distribution

39. Not having waxy layer Having sunken stomata Cover with lots of hair Fine fibrous structures covers the stomatal opening Traps the vapor that come out to stomata Humidity increase into it Reduce transpiration Ex: nerium oleander Adaptation & Distribution

40. Stephen Hales (1972) devised three methods for measuring the rate of transpiration: By weighing potted plants By potometer By measuring the humidity of air Measurement Of Transpiration

41. By weighing potted plants Record decrease of weight over 3 hours Amount of water loss from the leaves Measurement Of Transpiration

42. Potometer Measurement Of Transpiration Rate of absorption proportional to transpiration rate

43. Measurement Of Transpiration

44. Measurement Of Transpiration

45. By Measuring the Humidity of Air This method can be used for measuring the rate respiration from single leaf. The leaf is enclosed in plexiglass chamber and sealed. Air is passed through the chamber at a definite flow rate. The humidity of the air before entering the chamber and after leaving the chamber is measure . Amount of water transpired= Relative humidity ( after closing the chamber) – Initial relative humidity of chamber Measurement Of Transpiration

46. Thornthwaite then derived an equation to provide evaporation estimates based on a series of observed evaporation measurement The first part of the Thornthwaite estimation technique (Thornthwaite, 1944, 1954) derives a monthly heat index ( i ) for a region based on the average temperature t (°C) for a month Thornthwaite equation of evapo -transpiration

47. Thornthwaite equation of evapo -transpiration

48. Factors Affecting Transpiration

49. Plants Parameters : Stomata: When stomata are open , transpiration rates increase; when they are closed, transpiration rates decrease. Number of Stomata: More stomata will provide more pores for transpiration. Number of Leaves: More leaves mean a bigger surface area and stomata for transpiration. Factors Affecting Transpiration

50. Cuticle: The thicker the cuticle layer on a leaf surface, the slower the transpiration rate. Leaf Area (Transpiring Area): A plant with large leaf area will show more transpi­ration than another plant with less leaf area Root/Shoot Ratio: A low root/shoot ratio decreases the rate of transpiration while a high ratio increases the rate of transpiration . Factors Affecting Transpiration

51. Mesophyll: Compact mesophyll reduces transpiration while a loose mesophyll increases transpiration. Leaf Modifications : Formation of prickles, leaf spines, scaly leaves, phyllodes , phylloclades , are all modifications found in xerophytes to reduce transpi­ration. Factors Affecting Transpiration

52. Environmental Conditions: Light intensity : it warms the leaves up quicker. It also cause the stomata to open, thus more transpiration occurs during the day and the rate is higher on a sunny day compared to a cold dull day. Factors Affecting Transpiration

53. Humid atmosphere At low humidity there is a lower concentration of water molecules in the air around the leaves. This concentration gradient helps the transport of water molecules from the leaves by diffusion. High humidity means the air around the leaves is already saturated and has a higher concentration of water molecules than inside the leaves. Factors Affecting Transpiration

54. Temperature: An increase in the air temperature warms the water inside the leaves more quickly causing it to evaporate quicker. It also increases the capacity of the air to absorb more water . ROT Factors Affecting Transpiration

55. Wind: Transpiration relies on diffusion. Windy conditions cause the air molecules to be blown away from the leaves, preventing the air around the leaves becoming saturated with water molecules . Soil Water Factors Affecting Transpiration

56. Meteorology is a branch of the atmospheric sciences which includes atmospheric chemistry and atmospheric physics, with a major focus on weather forecasting. Hydrometeorology is a branch of meteorology and hydrology that studies the transfer of water and energy between the land surface and the lower atmosphere. Hydrometeorology is the science which deals with the movement of water and water vapour in the atmosphere Hydrometerology

57. Types Flood Tropical cyclone Drought Desertification Wildfire Hail Mudflow Hydrometerology

58. Hydro-meteorological Instruments: Hydrometerology

59. Soil thermometer, Psychrometer (Top to bottom)

60. Thank you Feel Free to ask any question