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Sub 1[1].8 form 5
- 1. BIOLOGY FORM 5 CHAPTER 1 : TRANSPORT
- 2. LEARNING OUTCOMES • To state what translocation is. • To explain the importance of translocation in plants. • To describe the process of transpiration. • To explain the importance of transpiration. • To describe the pathway of water from the soil to the leaves. • To state external conditions affecting transpiration
- 3. TR A N S L O C A TI ON • T h e t r a n s p o r t o f d is s o l v e d o r g a n ic f o o d s u b s t a n c e s b y t h e p h l o e m. IM P O R T A N C E O F T R A N S L O C A T IO N • Ensures a plant’s survival • Organic food molecules can be transported : – To the growing regions in the plant for growth & development – To the plant cells for metabolism – Downwards from the leaves to the storage organs such
- 6. T R A N S P IR A T IO N • The loss of water as water vapour from a living plant to the atmosphere due to evaporation. • M os t of th e wate r is los t th rou gh th e stomata of le ave s . • A s m all am ou nt is los t th rou gh th e cuticle or th rou gh th e lenticels in wood y s te m
- 7. • T hree main sites of transpiration are : – S T OM A T A – 90% of transpiration takes place through minute pores on leaves called stomata – C UT I C L E – 10% of transpiration takes place through the cuticle. The amount of water loss varies with the thickness of the waxy cuticle – L E NT I C E L S – small pores in the stem which allow gaseous exchange. Only small amounts of water are lost through the lenticels.
- 8. • Transpiration occurs mainly during the day when the stomata are opened. • Heat from the sun causes the water to evaporate from the walls of the spongy mesophyll cells. • The water vapour accumulates in the substomatal air chambers before diffusing from the plant through the open stomata
- 9. • Water move into the mesophyll cells by osmosis from the adjacent cell • Water flows from the xylem vessels along a chain of cells to the outermost mesophyll cell. • Water is pulled through the xylem vessels from the root to the
- 14. T h e I mp o r t a n c e o f T r a n s p ir a t io n • Creates a transpirational pull that pulls water & dissolved mineral ions from the root to the leaves. • Water supplied to the plant is used for photosynthesis & cell metabolism. Mineral ions is used for cell activities & growth & development of the plant.
- 15. • Water keeps the cell turgid give support to leaves & young stems (herbaceous plants). • To keep the plant cool, an important effect particularly in hot condition. • Water evaporates from the plants to the atmosphere faster than it can be absorbed from the soil, it is withdrawn from the plant cells flaccid – leading to wilting
- 17. P A TH WA Y O F WA TE R F R O M T H E S O IL T O TH E L E A VE S • Water & mineral ions are absorbed by young roots with thin epidermis. (osmotic forces + active transport) • The pressure of root hairs increases the surface area for absorption. • The cell sap in the root hair cell contains sugars, amino acids, & minerals more concentrated than the surrounding dilute soil solution.
- 18. • Wate r d iffu s e s into th e root ce lls b y os m os is . • Th e e ntry of wate r into th e root ce lls d ilu te s its ce ll s ap . • Th e ce ll s ap of th e ad j nt corte x ace ce ll is now m ore conce ntrate d wate r m ole cu le s d iffu s e into th e ad j nt root ce ll. ace
- 19. • The process continues & water is transported from one root cell to another by osmosis. • In the cells of the endodermis, mineral ions are actively pumped from these cells into the solution in the xylem vessels in the root. • Solution in xylem more concentrated water enters xylem by osmosis.
- 20. • This process creates an upward force called ROOT PRESSURE. • Helps to push water in the xylem up to a certain height in the plant. • Root pressure alone is insufficient to force the water to the top part of a tall tree. • Need CAPILLARITY ACTION & TRANSPIRATIONAL PULL.
- 21. G U T T A T IO N • In small plants, root pressure can push water all the way up the stem & out of special pores called hydathodes at the edges of leaves Guttation • Occurs on cool humid morning when the air is too saturated for the water drops to evaporate from the leaves.
- 23. TH E E XTE R N A L C O N D IT IO N S A F F E C T IN G T H E R A T E O F T R A N S P IR A T IO N • The external factors that affect the rate of evaporation. – Air movement – Temperature – Light intensity – Relative humidity
- 24. A IR MOVE ME NT • Movement of air carries away water molecules that have diffused from the leaves. • The faster the air movement (wind speed) the greater the rate of transpiration. • When there is little air movement/ in still air, water vapour diffusing out of the leaf accumulates around the stomata. • Decreases the concentration gradient of water, the transpiration rate reduces.
- 25. TE M P E R A TU R E • A rise in temperature increases the kinetic energy of water molecules & increase the rate of evaporation (transpiration). • Lowers the relative humidity of the air increase the rate of transpiration. • Temperature low, kinetic energy of water molecules is decreased. • Relative humidity of the air is higher decrease the rate of transpiration
- 26. L IG H T IN T E N S IT Y • The light intensity increased, the rate of evaporation increases. • Light not effects evaporation but causes the stomata to open increasing water loss from the plant. • At night @ dark, stomata close
- 27. ð ^ • The rate of evaporation depends on the difference in concentration of water molecules in the sub-stomatal spaces & in the surrounding atmosphere. • The lower the relative humidity of the surrounding atmosphere, the faster will the water vapour escape from the stomata. • High relative humidity reduces water loss.
- 28. ROOT PRESSURE • If a stem is cut just above ground level, a considerable amount of sap will exude from the cut stump, showing that there is a force pushing water up the stem from the roots. • Its ROOT PRESSURE The result of an active process in which energy from ATP is used.
- 29. ROOT PRESSURE • Root pressure alone is not strong enough to drive water to the tops of tall trees at the speeds achieved during a normal growing season.
- 30. COHESION & ADHESION OF WATER • COHESION = the force of attraction between the same molecules • The cohesive forces between water molecules hold the continuous columns of water together & when water transpires from the leaf, the whole of the water column moves up the xylem vessels.
- 31. • ADHESION = the force of attraction between different molecules • Water molecules tend to adhere to the walls of the xylem vessels. • The adhesive forces can support a considerable mass of water. • Cohesion + adhesion = capillarity (the rise of water in a capillary tube).
- 32. O P E N IN G & C L O S IN G O F • Dicotyledonous O Mon the lower surface S T leaves = A T A • Monocotyledonous leaves = both the upper & lower surfaces. • Each stoma consists of a pair of kidney-shaped guard cells surrounding a stomatal pore.
- 33. • A guard cell has a thinner elastic outer cell wall & a thicker, less elastic inner cell wall. It has a nucleus, cytoplasm & chloroplasts. • The opening & closing of the stomata in the leaf controls the diffusion of CO2 & O2 into & out of a leaf as well as the rate of transpiration.
- 34. S TOMA TA L OPE NING • DAY : photosynthesis occurs & CO2 level is low in the leaf. • Potassium ions (K+) diffuse from surrounding epidermal subsidiary cells into the guard cells. • In many plant species, starch stored in the guard cell is converted into malate. • The accumulation of K+ & malate ions increase the osmotic pressure in the guard cell.
- 35. • Water enters by osmosis from surrounding epidermal cells into the guard cells • Two guard cells become turgid & curve outward & the stoma opens.
- 36. S TO M A TA L • NIGHT : no photosynthesis &G level C L O S I N CO2 is high. Potassium ions move out of the guard cells into the epidermal cells. • Malate ions are converted to starch. The osmotic pressure in the guard cells decreases. • Water diffuses out to the surrounding epidermal cells by osmosis.
- 37. • Guard cells become flaccid & stoma closes. • The stomata also close, when there is insufficient water supply & the transpiration rate is high.
- 38. Rasulullah bersabda: Yang menjadikan orang mukmin itu pemurah adalah agamanya,yang menjadikan orang mukmin itu mempunyai kehormatan adalah akalnya dan yang menjadikan orang mukmin itu mulia adalah budi pekertinya