Uploaded byMahdAli3
PPT, PDF337 views

9_ Transport in Plants.ppt

The document discusses transport in plants. There are two main transport tissues in flowering plants: xylem and phloem. Xylem transports water and mineral salts upwards from the roots through hollow tubes reinforced with lignin. Phloem transports sucrose and amino acids throughout the plant through sieve tubes and companion cells. Water is absorbed into the roots through osmosis and transported upwards through the plant via root pressure, capillary action, and transpiration pull. Transpiration is the loss of water vapor from leaves and creates a pulling force. Various environmental factors like temperature, humidity, light intensity, and wind affect the rate of transpiration.

Embed presentation

Download to read offline
Transport in Plants
Transport system of flowering plants • The vessels that transport materials in plants is known as the vascular tissue • There are two main transport tissues: • Xylem • Phloem
Xylem • Functions • Conduct water and mineral salts from roots to stems and leaves • Provide mechanical support • Structure • Xylem tissue consists mainly of xylem vessels • A xylem vessel is a long hollow tube made of many dead cells • Inner walls are strengthened by lignin – rings or spirals
Lignin Patterns Rings (annular) Spiral Scalariform Reticulate Pitted
Adaptations of the Xylem Feature Adaptation Empty lumen without protoplasm or cross walls Reduces resistance to water flow, allowing for rapid transport of water Walls thickened with lignin Lignin is hard and rigid. It prevents collapse of the vessel
Phloem • Functions: • Translocates sucrose and amino acids from the leaves to other parts of the plant. • Structure • Consists of two elements: sieve tube and companion cells
Phloem a) Sieve tube • Sieve tube cells or sieve tube elements • Elongated, thin walled LIVING cells • Cells separated by sieve plates • Cross walls that are perforated with pores = sieve • Sucrose is loaded into the sieve tube by active transport. Sieve tube cell Xylem Sieve plate
Sieve tube cells • Mature sieve-tubes has thin lining of cytoplasm. • Nucleus, central vacuole as well as most organelles are disintegrated. • Degenerated protoplasm • Sieve tube cells need help to sustain life • Companion cells ‘accompany’ them and ‘feed’ them
Companion cells • Each sieve tube cell has a companion cell beside it • This carries out the metabolic processes to keep both cells alive • Structure: • narrow, thin-walled, many mitochondria. Has cytoplasm and a nucleus • Function: • Provides nutrients and helps sieve tube cells transport food
Phloem Feature Adaptation Companion cells have many mitochondria Provides energy needed for companion cell to load sugars from mesophyll cells into sieve tubes by active transport Sieve plates have holes Allows rapid flow of manufactured food substances through sieve tubes
Differences between Xylem and Phloem Xylem Phloem Consists of dead cells Consists of living cells -Transports water and mineral salts -Provide mechanical support to the plant Transports sugar and amino acids Transport is unidirectional Transport –bi directional, upwards and downwards Substances are loaded by passive transport - osmosis, and transported by root pressure, capillary action, transpiration pull Substances are loaded by active transport, diffusion
Vascular tissues (Stems) • The xylem and phloem are grouped together to form a vascular bundle • The phloem lies outside the xylem • The two are separated by the CAMBIUM - The cambium divides and differentiates to form new xylem and phloem tissues
Vascular Bundle 2 pith 1 vascular bundles 3 4 cortex 5 epidermis xylem cambium phloem vascular bundle
Vascular bundles (Stems) • A stem will contain many vascular bundles arranged in a ring • This surrounds a central region called the pith • The region outside the pith and between the vascular bundles is called the cortex • Both cortex and pith store up food substances e.g. starch • The stem is covered by a layer of cells called the epidermis • The epidermis is protected by the cuticle • This is a waxy, waterproof layer • Reduces loss of water by evaporation
Phloem Cambium Xylem Vascular Bundle Pith Cortex Epidermis Cuticle Vascular bundles (Stems)
• The xylem and phloem alternate with each other • Pericycle surrounds the vascular tissues • Endodermis surrounds the pericycle • Cortex acts as storage tissue Pericycle Endodermis Cortex Vascular tissues (Roots) • Tubular outgrowth of an epidermal cell • Increases surface area to volume ratio • Increases efficiency of water/mineral salt absorption
• Piliferous layer: this is a epidermal layer that bears root hairs • Cuticle is absent in the piliferous layer 1 xylem and phloem alternate with each other. 2 cortex endodermis 3 piliferous layer 4 root hair Vascular tissues (Roots)
Regions of a root Root cap -Covers root tip -Protects young cells from injury Growing zone - Small young cells that actively divide Zone of elongation -Cells elongate -Causes increase in root length Zone of maturation -Bears numerous root hairs -Where most of the water and mineral salts are absorbed
Translocation • Translocation • The movement of food substances e.g. sugars and amino acids in a plant • Translocation studies • Aphid studies • Ringing experiment • Use of radioactive isotopes
Translocation Pathway • Sugars form in leaf cells, and are actively transported by companion cells (loaded) into phloem. • Bulk flow of water pushes sap to sinks. Sink cells actively remove sugars, and convert them to starches. Water is recycled through xylem.
1. Aphid studies • Aphids are insects that feed on plant juices • They have a long mouth piece called a proboscis • The aphid uses its proboscis to penetrate a leaf/stem and feed
1. Aphid studies • When the aphid is feeding, it is anesthetized with CO2 • The body is cut off, leaving the embedded proboscis • Liquid that exudes from the proboscis contains sucrose and amino acids • Sectioning the stem shows the proboscis is in the phloem sieve tube
2. Ringing Experiment • Cut off a ring of bark, including the phloem, but leaving the xylem • Immerse in water and observe • Swelling observed above the cut • Due to accumulation of organic solutes that came from higher up the tree and could no longer continue downward because of the disruption of the phloem. • Later, the bark below the girdle died because it no longer received sugars from the leaves. • Eventually the roots, and then the entire tree, died.
3. Use of radioactive isotopes • Carbon-14 (14C) is a radioactive isotope of carbon • If 14CO2 is supplied to the plant, it will be fixed in the glucose upon photosynthesis: • 14C6H12O6 • When the stem is cut and placed on a X-ray film, only the phloem contains radioactivity
Absorption of water 1.Into the roots • By osmosis 2. Up the stem • Root pressure • Capillary action • Transpiration pull 3. Out of the leaves • Transpiration
Entry of water into a plant cytoplasm vacuole nucleus cell wall cell surface membrane of root hair cell film of liquid (dilute solution of mineral salts) soil particles Each root hair is a fine tubular outgrowth of an epidermal cell. It grows between the soil particles, coming into close contact with the water surrounding them. 1 1 The thin film of liquid surrounding each soil particle is a dilute solution of mineral salts. 2 2
Entry of water into a plant The sap in the root hair cell is a relatively concentrated solution of sugars and various salts. Thus, the sap has a lower water potential than the soil solution. These two solutions are separated by the partially permeable cell surface membrane of the root hair cell. Water enters the root hair by osmosis. 3 The entry of water dilutes the sap. The sap of the root hair cell now has a higher water potential than that of the next cell (cell B). Hence, water passes by osmosis from the root hair cell into the inner cell. 4 Similarly, water passes from cell B into the next cell (cell C) of the cortex. This process continues until the water enters the xylem vessels and moves up the plant. 5 A B C xylem phloem cortex root hair piliferous layer water entering the root hair 3 4 5
1. Into the roots • Root hairs are fine tubular outgrowths • Surrounded by soil particles • Dilute solution of mineral salts surrounds soil particles
Absorption in roots Root hair cell sap is a concentrated solution of sugars and salts. The more dilute soil solution has a higher water potential than the cell sap Water enters the cell sap from the soil solution by osmosis, down the water potential gradient Water entry dilutes the sap and raises the water potential Root hair cell has higher water potential than neighbouring cell Water moves into neighbouring cell by osmosis, down the w.p.g Process repeats and water moves from cell to cell, through the root cortex until it enters the xylem
Ions and mineral salts 1. Diffusion –when the concentration of minerals salts in the soil solution is higher than that in the root hair cell. 2. Active transport –when the concentration of ions in the soil solution is lower than that in the root hair cell sap. 3. The energy comes from cellular respiration in the root hair cells
Adaptations of the root hair cell Feature Adaptation 1 Long and narrow Increases SA:V, thus increasing rate of absorption of water and mineral salts 2 Has cell surface membrane Partially permeable Maintains high conc. of sugars, amino acids and salts in cell sap. Results in lower water potential than soil solution so water can enter by osmosis 3 Is living Able to provide energy for active transport of ions into cell 4 Has protein transporters Able to transport specific mineral ions into the cell.
2. Up the stem a. Root pressure • Root cells actively pump inorganic ions into the xylem and the root endodermis holds the ions there. • As ions accumulate in the xylem, water enters by osmosis, pushing the xylem sap upward ahead of it. • This force, called root pressure, can push xylem sap up to a few metres. • Root pressure is not enough to bring water up all trees.
2. Up the stem b. Capillary action - If water is present in a narrow (capillary) tube, forces of attraction exist between: - Water molecules - Water molecules and surface of the tube - Causes water to move up the tubes - Effect is called capillary action - Cannot account for water rising up a tall tree
Up the stem c. Transpiration pull - Transpiration: Loss of water vapours from aerial parts of plant, especially through stomata of leaves - Transpiration pull: Suction force caused by transpiration - Main factor that causes water to move up the xylem - Transpiration stream: Stream of water moving up
Why is transpiration important? • Draws water and mineral salts from the roots to the stems and the leaves. • Evaporation of water from the cells in the leaves removes latent heat of vaporisation, so the plant is cooled. • Water transported to the leaves is used for photosynthesis and maintaining the turgidity of the leaf cells.
ENVIRONMENTAL FACTORS THAT AFFECT TRANSPIRATION 1. Temperature of air 2. Air humidity 3. Light intensity 4. Wind/air movement 5. Carbon dioxide concentration
1. Temperature of air • Higher temperatures increases the rate of evaporation • The higher the temperature, the greater the rate of transpiration 30 T degrees Stomata closed
2. Air Humidity • Air inside leaf is saturated with water vapour • Increasing the humidity of the air will decrease the water vapour concentration gradient between the leaf and the atmosphere, therefore decreasing the rate of transpiration • The lower the humidity, the faster the rate of transpiration T Humidity
3. Light Intensity • When light intensity is increases, guard cells become turgid. • The stomata opens, increasing the rate of transpiration. • When light intensity is reduced, the stomata closes. • In greater the light intensity, the greater the rate of transpiration Stomata closed T
4. Wind/air movement • Blows water vapour away at the surface of leaves • Increases concentration gradient between water vapour in the leaf and outside the leaf • This would increase transpiration • When the air is still, transpiration reduces or stops • The stronger the wind, the faster the rate of transpiration T Wind
5. Carbon dioxide concentration • When carbon dioxide concentration in the intercellular spaces of the leaf falls below a critical concentration, the stomata opens. This increases transpiration. • An increase in carbon dioxide concentration decreases the rate of transpiration. T Co2 concentration
Wilting • Turgor pressure of mesophyll cells supports the leaf and keep it firm and spread out widely to absorb sunlight for photosynthesis. • In strong sunlight, when the rate of transpiration exceeds the rate of absorption of water by the roots, the cells lose their turgor, become flaccid and the plant wilts. • Wilting also occurs in the soft stems of certain plants in which the stem mesophyll cells lose water. • If rate of transpiration > rate of water absorption, cells become flaccid and plant wilts • Advantages: Reduces rate of transpiration and thus, reduces water loss • Disadvantage: Stomata are closed, reducing entry of CO2. Rate of photosynthesis decreases
Plant adaptations • Xerophytes -- Plants that live in dry conditions • Adapted to preventing water loss and storing water • Hydrophytes – Water plants • Fully submerged plants adapted to receiving more sunlight • Partially submerged plants adapted to float • Floating plants adapted to float and compete for sunlight
Xerophytes Mechanism Adaptation Limit water loss Waxy stomata – Reduces water loss by transpiration Few stomata – Reduces transpiration rate Sunken stomata – hairs of grooves trap water vapour that diffuses out. Increases humidity around stomata, therefore reducing transpiration Reduced leaf size – Reduces exposed surface area Curled leaves – Reduces exposed surface area Water storage Succulent leaves Succulent stems Fleshy tubers
Hydrophytes Mechanism Adaptation - Thin/no cuticle. -Since cuticle is to prevent water loss, there is less need for cuticle Large intercellular air spaces – aids buoyancy Abundant stomata - No need to reduce water loss - Maximise gaseous exchange
Using a potometer 1. Insert plant into cork with hole 2. Smear opening with petroleum jelly – makes the apparatus airtight 3. Open tap to fill tube with water 4. As plant transpires, water moves to replace water lost in the plant. Bubble moves along capillary tube
The basic design of a potometer It consists of: *'''A length of capillary tube''‘ An air bubble is introduced to the capillary. As water is taken up by the plant, the bubble moves and its length of movement is measured by the scale attached with capillary tube . The distance the bubble travels in a given time is determined by the rate of transpiration by the plant. *''' A reservoir'''. By turning the tap on the reservoir, the position of the bubble can be set at the start of the experiment. Some designs of potometer use a syringe instead of a funnel with a tap. • '''A tube for holding the shoot'''. • In the diagram the shoot is held in place by inserting a rubber bung in the tube. The hole in the bung through which the shoot passes must be thoroughly greased with petroleum jelly to keep it airtight.
Setting up: # Cut a ''leafy'' shoot from a plant (e.g. Pelargonium) and plunge its base into water (try not to get any water on the leaves). This prevents the xylem from taking up any air. #Back in the laboratory, put the stem into a large sink full of water and carefully trim the shoot again, by cutting off the bottom '''under water''' with a sharp razor blade. Keep the leaves out of the water. #Immerse the whole of the potometer into the sink. Move it about until all the air bubbles come out. #Put the shoot stem into the bung, grease the joint with plenty of petroleum jelly, then put the bung into the potometer. #Make sure the tap is closed, then lift the whole ensemble out of the water. #Leave the end of the capillary tube out of the water until an air bubble forms then put the end into a beaker of water.
Using a potometer= Allow the bubble time to go around the corner and start at the beginning of the millimeter scale. Then measure how far the bubble moves in a given period of time. Repeat under different conditions and compare. The usual conditions to try are placing the plant in a bright light, placing it by a fan, and placing it in a humid atmosphere. If the surface area (both sides) of the leaves are measured then it is possible to compare the transpiration rates of different species of plant.
'Limitations of a potometer' # Introducing the air bubble is not easy. # The leafy shoot may not remain fully alive for as long as wanted. # Any changes in the outside air temperature may affect the position of the air bubble in the capillary tube.
Experiment to demonstrate Transpiration by Four-Leaf Experiment: Requirements: Four leaves, Vaseline and a string. Experiment: To demonstrate the transpiration from the leaf surface, four banyan leaves are taken. Both the surfaces of the A leaf, lower surface (with stomata) of B leaf, upper surface (without stomata) of C leaf are vaselined. The Vaseline is not applied on the D leaf. Now, as shown in the figure the leaves are hanged so that they may transpire freely.
Observation and Explanation: When the observations are taken after a day or two, they are as follows — the A leaf, which is vaselined on its both the surfaces, looks fresh and green, as no surface transpires. The B leaf is vaselined on its lower surface (with stomata), and transpiration takes place only from the upper surface which is negligible. This leaf also remains turgid and green like the A leaf. If few stomata are present on the upper surface of the leaf, then it shrivels to some extent. The C leaf is vaselined on its upper surface, which contains less number of stomata or no stomata. The transpiration takes place from the lower stomatal surface, and the leaf shrivels to a large extent. The D leaf is not vaselined and both the surfaces transpire freely releasing much water. The leaf wilts completely in this case. This experiment proves that the rate of stomatal transpiration is fairly higher than the cuticular transpiration.
Observation and Explanation: When the observations are taken after a day or two, they are as follows — the A leaf, which is vaselined on its both the surfaces, looks fresh and green, as no surface transpires. The B leaf is vaselined on its lower surface (with stomata), and transpiration takes place only from the upper surface which is negligible. This leaf also remains turgid and green like the A leaf. If few stomata are present on the upper surface of the leaf, then it shrivels to some extent. The C leaf is vaselined on its upper surface, which contains less number of stomata or no stomata. The transpiration takes place from the lower stomatal surface, and the leaf shrivels to a large extent.
Experiment to demonstrate that there is a loss in the total weight of plant due to transpiration: Requirements: 1. Spring balance (2), two leaves of almost equal size, test tube (2), water, vaseline and stand. Method: 1. Take two test tubes filled with water and close their mouth with a cork having a hole. 2. Insert the petiole of both the leaves, one in each test tube, and note that it is dipped in water. 3. Apply vaseline on both the surfaces of leaf ‘B’. 4. Connect both the spring balances with the stand and hang both the tubes on the hook of spring balances (Fig. 27).
5. Make both the corks air-tight by applying vaseline. 6. Note the weight of both the tubes. 7. Put the whole apparatus in light and wait for a few hours. Note the weight of both the tubes again.
It is observed that there is a clear loss in weight of test tube having leaf ‘A’ and there is no change in weight in leaf ‘B’. Results: Loss in the weight of leaf ‘A’ indicates that this is due to the process of transpiration because the leaf is continuously transpiring the water vapours. But on both the surfaces of leaf ‘B’ vaseline has been applied and so the leaf is not transpiring and so there is no change in its weight. These results clearly indicate that during the transpiration there is a loss in the total weight of the plant.Rate of transpiration can be calculated as shown below Rate of transpiration= loss in mass/time taken g/h
Experiment to demonstrate the water- lifting power of transpiration process: Requirements: Beaker, water, mercury, stand, capillary tube, vaseline, cork, plant twig, oil cloth. Method: 1. Take some amount of mercury in the beaker and invert a wide-mouthed capillary tube over it. 2. Fill the capillary tube with water. 3. Insert the plant twig into the hole of the cork in such a way so that its cut end is dipped in the water. 4. Apply the vaseline on the cork and hole to make it air-tight (To make the cork region air-tight oil cloth may also be used instead of vaseline). 5. Keep the whole apparatus in sun. 6. Note the mercury level in the capillary tube and wait for some time.
Observations: Mercury level rises in the capillary tube(Fig.16).
Results: Mercury level rises in the capillary tube because of the pull or suction exerted by the transpiration process. Aerial parts of the plants are continuously evaporating water because of transpiration process. To compensate this loss the water is absorbed by the plant and lifted. So, the space in the capillary tube, which was first occupied by this absorbed water, is now occupied by the mercury. This demonstrates the water-lifting power of the transpiration process.
WILTING
WILTING Wilting is the loss of rigidity of non-woody parts of plants. This occurs when the turgor pressure in non-lignified plant cells falls towards zero, as a result of diminished water in the cells.The cells become flaccid. The rate of loss of water from the plant is greater than the absorption of water in the plant. Lower water availability may result from: • drought conditions, where the soil moisture drops below conditions most favorable for plant functioning; • the temperature falls to the point where the plant's vascular system cannot function; • high salinity, which causes water to diffuse from the plant cells and induce shrinkage; • saturated soil conditions, where roots are unable to obtain sufficient oxygen for cellular respiration, and so are unable to transport water into the plant; or • bacteria or fungi that clog the plant's vascular system.
Advantages and Disadvantages of wilting Advantage: with the guard cells not turgid, the stomata close and the rate of water loss is reduced. Rate of transpiration is reduced because the leaf folds up that is reducing the surface that is exposed to sunlight. Disadvantage: Rate of photosynthesis reduced because water becomes the limiting factor .Also as the stomata are closed,gas exchange in the leaves slows, and therefore so does photosynthesis.
9_ Transport in Plants.ppt

More Related Content

PPT
heat-and-temperature-G9-final.ppt for students
bytrixianyllea
 
PPTX
Nutrition in animals
byPunya M
 
PPT
Chapter 11 transport_in_plants
byPunya M
 
PPTX
Class-6th Science chapter-12 Electricity and Circuits part-1
byAakankshaYaduvanshi
 
PPT
Grade 9, U1-L5 Physical and chemical changes
bygruszecki1
 
PPT
TRANSPORTATION IN PLANTS AND CIRCULATION IN ANIMALS.ppt
byAvi's Micro World
 
PPTX
The Fundamental Unit of Life (Prashant Kirad).pptx
bycanadaxyz32
 
PPTX
Class -7 Science Chapter-1 nutrition in plants,
byKaramBora
 
heat-and-temperature-G9-final.ppt for students
bytrixianyllea
 
Nutrition in animals
byPunya M
 
Chapter 11 transport_in_plants
byPunya M
 
Class-6th Science chapter-12 Electricity and Circuits part-1
byAakankshaYaduvanshi
 
Grade 9, U1-L5 Physical and chemical changes
bygruszecki1
 
TRANSPORTATION IN PLANTS AND CIRCULATION IN ANIMALS.ppt
byAvi's Micro World
 
The Fundamental Unit of Life (Prashant Kirad).pptx
bycanadaxyz32
 
Class -7 Science Chapter-1 nutrition in plants,
byKaramBora
 

What's hot

PPTX
Asexual reproduction
byMarthese Azzopardi
 
PPTX
RESPIRATION IN ORGANISMS-1 CLASS-VII CBSE
bySONU ACADEMY
 
PPT
VII-nutrition in plants
bySUSHREESWAYAMSMITA
 
PPTX
Transport in plants
bychenghong03
 
PDF
Class 9 biology chapter 1
byVinay Kumar Maurya
 
PDF
ICSE Class VIII Chemistry Matter Around Us - TopperLearning
byAlok Singh
 
PPT
Mass and Volume of Matter
byHannah D
 
PDF
Class 9 chemistry chapter 2
byVinay Kumar Maurya
 
PPT
Transport in plant slides
byAlex Chiam
 
PDF
Chapter - 1, Nutrition in Plants, Science, Class 7
byShivam Parmar
 
PPTX
Class 7th Chapter 6 PHYSICAL AND CHEMICAL CHANGES.pptx
byMVHerwadkarschool
 
PPT
motion class 9 physics
byshashankgarg57
 
PPTX
Transport in animals
bySian Ferguson
 
PPTX
CBSE Class 9 Science Chapter-1 Matter in our surroundings
byAarthiSam
 
PPTX
Fibre to fabric Class VII
byDeepa Unni
 
PPTX
Nutrition in plants
byBalkrishan Sharma
 
PPTX
Fun with magnets class 6
byManik Bhola
 
PPTX
Transport in plants
byMagdaléna Kubešová
 
PPTX
CLASS 7 ENERGY
bySouvikChatterjee53
 
PPTX
Cell structure and function for class 8
byAashuutoshh
 
Asexual reproduction
byMarthese Azzopardi
 
RESPIRATION IN ORGANISMS-1 CLASS-VII CBSE
bySONU ACADEMY
 
VII-nutrition in plants
bySUSHREESWAYAMSMITA
 
Transport in plants
bychenghong03
 
Class 9 biology chapter 1
byVinay Kumar Maurya
 
ICSE Class VIII Chemistry Matter Around Us - TopperLearning
byAlok Singh
 
Mass and Volume of Matter
byHannah D
 
Class 9 chemistry chapter 2
byVinay Kumar Maurya
 
Transport in plant slides
byAlex Chiam
 
Chapter - 1, Nutrition in Plants, Science, Class 7
byShivam Parmar
 
Class 7th Chapter 6 PHYSICAL AND CHEMICAL CHANGES.pptx
byMVHerwadkarschool
 
motion class 9 physics
byshashankgarg57
 
Transport in animals
bySian Ferguson
 
CBSE Class 9 Science Chapter-1 Matter in our surroundings
byAarthiSam
 
Fibre to fabric Class VII
byDeepa Unni
 
Nutrition in plants
byBalkrishan Sharma
 
Fun with magnets class 6
byManik Bhola
 
Transport in plants
byMagdaléna Kubešová
 
CLASS 7 ENERGY
bySouvikChatterjee53
 
Cell structure and function for class 8
byAashuutoshh
 

Similar to 9_ Transport in Plants.ppt

PPT
transport in plants
byKhadijaparekh93
 
PPTX
9. Transport in Plants.pptx
bysahibzadamohsinbaloc
 
PPT
Transport in plants
byHoang Phuong Linh
 
PPT
Chapter 9 transport in plants lecture
byXu Jia Xian
 
PPT
How plants survive grade 11
bymajoydrew
 
PPT
Cambridge AS Biology plant revision
byGuerillateacher
 
PPTX
Transportation In Plants
byRukhma Aijaz
 
PPT
Transport in plant slides
byAlex Chiam
 
PPT
Chapter 9 Transport in Plants Lesson 2 - Xylem and Phloem structure and function
byj3di79
 
PPT
Transport in Plants-Vascular System-Xylem and Phloem
bygaviolasarahjane7
 
PPTX
Transport in flowering plants
byShanice Smith
 
PPTX
Transport system in plants
byFaiz Abdullah
 
PPT
Transport in plants 2015
bySeval XD
 
PPTX
Biology Form 5 chapter 1.7 & 1.8 (Transport in Plants)
bymellina23
 
PPT
Transportation in plant
bySantosh Kumar Kar
 
PPTX
AS Level Biology - 7) Plant Transport
byArm Punyathorn
 
PPTX
BIO MODULE 1.pptx (hello pls see this lmfaoooo)
byaliviaislam49
 
PPTX
hgyg ujhgb ghvj gbb h plant transportio.pptx
byluiisennghiimbwasha
 
PPTX
独中高中生物Chapter 8 transport in plants
byYee Sing Ong
 
PPTX
Bio transport in flowering plants
byWali Arif
 
transport in plants
byKhadijaparekh93
 
9. Transport in Plants.pptx
bysahibzadamohsinbaloc
 
Transport in plants
byHoang Phuong Linh
 
Chapter 9 transport in plants lecture
byXu Jia Xian
 
How plants survive grade 11
bymajoydrew
 
Cambridge AS Biology plant revision
byGuerillateacher
 
Transportation In Plants
byRukhma Aijaz
 
Transport in plant slides
byAlex Chiam
 
Chapter 9 Transport in Plants Lesson 2 - Xylem and Phloem structure and function
byj3di79
 
Transport in Plants-Vascular System-Xylem and Phloem
bygaviolasarahjane7
 
Transport in flowering plants
byShanice Smith
 
Transport system in plants
byFaiz Abdullah
 
Transport in plants 2015
bySeval XD
 
Biology Form 5 chapter 1.7 & 1.8 (Transport in Plants)
bymellina23
 
Transportation in plant
bySantosh Kumar Kar
 
AS Level Biology - 7) Plant Transport
byArm Punyathorn
 
BIO MODULE 1.pptx (hello pls see this lmfaoooo)
byaliviaislam49
 
hgyg ujhgb ghvj gbb h plant transportio.pptx
byluiisennghiimbwasha
 
独中高中生物Chapter 8 transport in plants
byYee Sing Ong
 
Bio transport in flowering plants
byWali Arif
 

Recently uploaded

PPTX
Cultivation Practice of Chilli and sweet Pepper.pptx
byUmeshTimilsina1
 
PPTX
Cultivation practice of Cucumber, Pumpkin and summer squash in Nepal.pptx
byUmeshTimilsina1
 
PDF
The Industrialisation of Deception: An Analysis of the 2024 Cybercrime Landscape
bykrutivyas2005
 
PPTX
1. Importance, scope and constraints of vegetable and spice crop production i...
byUmeshTimilsina1
 
PDF
Teaching and Learning (BD1TL) - B.Ed TNTEU
byDr Raja Mohammed T
 
PDF
Result Analysis of the Pre Board 2025 .pdf
byDirectorate of Education Delhi
 
PPTX
What is Epiphany? A Visual introduction to this amazing liturgical season
bySteve Thomason
 
PPTX
Cultivation Practice of Major Cole crops in Nepal.pptx
byUmeshTimilsina1
 
PPT
Blood Grouping.ppt - Hematology -Physiology
bykishorkumar396
 
PPTX
YSPH VMOC Special Report - Measles - The Americas 12-28 2025 .pptx
byYale School of Public Health - The Virtual Medical Operations Center (VMOC)
 
PDF
Gaming Quiz 2025- 27th October 2025, Quiz Club NITW
byQuiz Club NITW
 
PDF
Road Safety Calendar-2026 Courtesy - IYSO Team India - Safer Indian Roads
byIndian Youth Secured Organisation
 
PPTX
Cultivation Practice of Tomato in Nepal.pptx
byUmeshTimilsina1
 
PDF
India Cybercrime Threats & Response 2025: Digital Arrests, 1930 Helpline & Ze...
bySanjay Rathod
 
PPTX
OCCULTISM IN JEHOVAH'S WITNESSES' ARTWORK
byDaniel Barnea
 
PPTX
Non aqueous titration First Year B. Pharm.pptx
byMs. Ashatai Patil
 
PDF
Plant Respiration.pdf Remedial Biology Unit-5 B.Pharm 1st Year
bySaurabh Dubey
 
PPTX
L5 DRG Pulsed Radiofrequency ablation.pptx
bySandeep Margan
 
PDF
Renewable Energy Resources Unit 2 Easy notes (EduShine Classes).pdf
byaaquib913
 
PDF
GDGoC TAE Orientation presentation for WOW-Verse hackathon
bymayurpatiltae
 
Cultivation Practice of Chilli and sweet Pepper.pptx
byUmeshTimilsina1
 
Cultivation practice of Cucumber, Pumpkin and summer squash in Nepal.pptx
byUmeshTimilsina1
 
The Industrialisation of Deception: An Analysis of the 2024 Cybercrime Landscape
bykrutivyas2005
 
1. Importance, scope and constraints of vegetable and spice crop production i...
byUmeshTimilsina1
 
Teaching and Learning (BD1TL) - B.Ed TNTEU
byDr Raja Mohammed T
 
Result Analysis of the Pre Board 2025 .pdf
byDirectorate of Education Delhi
 
What is Epiphany? A Visual introduction to this amazing liturgical season
bySteve Thomason
 
Cultivation Practice of Major Cole crops in Nepal.pptx
byUmeshTimilsina1
 
Blood Grouping.ppt - Hematology -Physiology
bykishorkumar396
 
YSPH VMOC Special Report - Measles - The Americas 12-28 2025 .pptx
byYale School of Public Health - The Virtual Medical Operations Center (VMOC)
 
Gaming Quiz 2025- 27th October 2025, Quiz Club NITW
byQuiz Club NITW
 
Road Safety Calendar-2026 Courtesy - IYSO Team India - Safer Indian Roads
byIndian Youth Secured Organisation
 
Cultivation Practice of Tomato in Nepal.pptx
byUmeshTimilsina1
 
India Cybercrime Threats & Response 2025: Digital Arrests, 1930 Helpline & Ze...
bySanjay Rathod
 
OCCULTISM IN JEHOVAH'S WITNESSES' ARTWORK
byDaniel Barnea
 
Non aqueous titration First Year B. Pharm.pptx
byMs. Ashatai Patil
 
Plant Respiration.pdf Remedial Biology Unit-5 B.Pharm 1st Year
bySaurabh Dubey
 
L5 DRG Pulsed Radiofrequency ablation.pptx
bySandeep Margan
 
Renewable Energy Resources Unit 2 Easy notes (EduShine Classes).pdf
byaaquib913
 
GDGoC TAE Orientation presentation for WOW-Verse hackathon
bymayurpatiltae
 

9_ Transport in Plants.ppt

  • 1.
  • 2.
    Transport system of floweringplants • The vessels that transport materials in plants is known as the vascular tissue • There are two main transport tissues: • Xylem • Phloem
  • 3.
    Xylem • Functions • Conductwater and mineral salts from roots to stems and leaves • Provide mechanical support • Structure • Xylem tissue consists mainly of xylem vessels • A xylem vessel is a long hollow tube made of many dead cells • Inner walls are strengthened by lignin – rings or spirals
  • 4.
  • 5.
    Adaptations of theXylem Feature Adaptation Empty lumen without protoplasm or cross walls Reduces resistance to water flow, allowing for rapid transport of water Walls thickened with lignin Lignin is hard and rigid. It prevents collapse of the vessel
  • 6.
    Phloem • Functions: • Translocatessucrose and amino acids from the leaves to other parts of the plant. • Structure • Consists of two elements: sieve tube and companion cells
  • 7.
    Phloem a) Sieve tube •Sieve tube cells or sieve tube elements • Elongated, thin walled LIVING cells • Cells separated by sieve plates • Cross walls that are perforated with pores = sieve • Sucrose is loaded into the sieve tube by active transport. Sieve tube cell Xylem Sieve plate
  • 8.
    Sieve tube cells •Mature sieve-tubes has thin lining of cytoplasm. • Nucleus, central vacuole as well as most organelles are disintegrated. • Degenerated protoplasm • Sieve tube cells need help to sustain life • Companion cells ‘accompany’ them and ‘feed’ them
  • 9.
    Companion cells • Eachsieve tube cell has a companion cell beside it • This carries out the metabolic processes to keep both cells alive • Structure: • narrow, thin-walled, many mitochondria. Has cytoplasm and a nucleus • Function: • Provides nutrients and helps sieve tube cells transport food
  • 10.
    Phloem Feature Adaptation Companion cellshave many mitochondria Provides energy needed for companion cell to load sugars from mesophyll cells into sieve tubes by active transport Sieve plates have holes Allows rapid flow of manufactured food substances through sieve tubes
  • 11.
    Differences between Xylem andPhloem Xylem Phloem Consists of dead cells Consists of living cells -Transports water and mineral salts -Provide mechanical support to the plant Transports sugar and amino acids Transport is unidirectional Transport –bi directional, upwards and downwards Substances are loaded by passive transport - osmosis, and transported by root pressure, capillary action, transpiration pull Substances are loaded by active transport, diffusion
  • 12.
    Vascular tissues (Stems) •The xylem and phloem are grouped together to form a vascular bundle • The phloem lies outside the xylem • The two are separated by the CAMBIUM - The cambium divides and differentiates to form new xylem and phloem tissues
  • 13.
    Vascular Bundle 2 pith 1vascular bundles 3 4 cortex 5 epidermis xylem cambium phloem vascular bundle
  • 16.
    Vascular bundles (Stems) •A stem will contain many vascular bundles arranged in a ring • This surrounds a central region called the pith • The region outside the pith and between the vascular bundles is called the cortex • Both cortex and pith store up food substances e.g. starch • The stem is covered by a layer of cells called the epidermis • The epidermis is protected by the cuticle • This is a waxy, waterproof layer • Reduces loss of water by evaporation
  • 17.
  • 18.
    • The xylemand phloem alternate with each other • Pericycle surrounds the vascular tissues • Endodermis surrounds the pericycle • Cortex acts as storage tissue Pericycle Endodermis Cortex Vascular tissues (Roots) • Tubular outgrowth of an epidermal cell • Increases surface area to volume ratio • Increases efficiency of water/mineral salt absorption
  • 19.
    • Piliferous layer:this is a epidermal layer that bears root hairs • Cuticle is absent in the piliferous layer 1 xylem and phloem alternate with each other. 2 cortex endodermis 3 piliferous layer 4 root hair Vascular tissues (Roots)
  • 20.
    Regions of aroot Root cap -Covers root tip -Protects young cells from injury Growing zone - Small young cells that actively divide Zone of elongation -Cells elongate -Causes increase in root length Zone of maturation -Bears numerous root hairs -Where most of the water and mineral salts are absorbed
  • 22.
    Translocation • Translocation • Themovement of food substances e.g. sugars and amino acids in a plant • Translocation studies • Aphid studies • Ringing experiment • Use of radioactive isotopes
  • 23.
    Translocation Pathway • Sugarsform in leaf cells, and are actively transported by companion cells (loaded) into phloem. • Bulk flow of water pushes sap to sinks. Sink cells actively remove sugars, and convert them to starches. Water is recycled through xylem.
  • 24.
    1. Aphid studies •Aphids are insects that feed on plant juices • They have a long mouth piece called a proboscis • The aphid uses its proboscis to penetrate a leaf/stem and feed
  • 25.
    1. Aphid studies •When the aphid is feeding, it is anesthetized with CO2 • The body is cut off, leaving the embedded proboscis • Liquid that exudes from the proboscis contains sucrose and amino acids • Sectioning the stem shows the proboscis is in the phloem sieve tube
  • 33.
    2. Ringing Experiment •Cut off a ring of bark, including the phloem, but leaving the xylem • Immerse in water and observe • Swelling observed above the cut • Due to accumulation of organic solutes that came from higher up the tree and could no longer continue downward because of the disruption of the phloem. • Later, the bark below the girdle died because it no longer received sugars from the leaves. • Eventually the roots, and then the entire tree, died.
  • 34.
    3. Use ofradioactive isotopes • Carbon-14 (14C) is a radioactive isotope of carbon • If 14CO2 is supplied to the plant, it will be fixed in the glucose upon photosynthesis: • 14C6H12O6 • When the stem is cut and placed on a X-ray film, only the phloem contains radioactivity
  • 37.
    Absorption of water 1.Intothe roots • By osmosis 2. Up the stem • Root pressure • Capillary action • Transpiration pull 3. Out of the leaves • Transpiration
  • 38.
    Entry of waterinto a plant cytoplasm vacuole nucleus cell wall cell surface membrane of root hair cell film of liquid (dilute solution of mineral salts) soil particles Each root hair is a fine tubular outgrowth of an epidermal cell. It grows between the soil particles, coming into close contact with the water surrounding them. 1 1 The thin film of liquid surrounding each soil particle is a dilute solution of mineral salts. 2 2
  • 39.
    Entry of waterinto a plant The sap in the root hair cell is a relatively concentrated solution of sugars and various salts. Thus, the sap has a lower water potential than the soil solution. These two solutions are separated by the partially permeable cell surface membrane of the root hair cell. Water enters the root hair by osmosis. 3 The entry of water dilutes the sap. The sap of the root hair cell now has a higher water potential than that of the next cell (cell B). Hence, water passes by osmosis from the root hair cell into the inner cell. 4 Similarly, water passes from cell B into the next cell (cell C) of the cortex. This process continues until the water enters the xylem vessels and moves up the plant. 5 A B C xylem phloem cortex root hair piliferous layer water entering the root hair 3 4 5
  • 40.
    1. Into theroots • Root hairs are fine tubular outgrowths • Surrounded by soil particles • Dilute solution of mineral salts surrounds soil particles
  • 41.
    Absorption in roots Roothair cell sap is a concentrated solution of sugars and salts. The more dilute soil solution has a higher water potential than the cell sap Water enters the cell sap from the soil solution by osmosis, down the water potential gradient Water entry dilutes the sap and raises the water potential Root hair cell has higher water potential than neighbouring cell Water moves into neighbouring cell by osmosis, down the w.p.g Process repeats and water moves from cell to cell, through the root cortex until it enters the xylem
  • 42.
    Ions and mineralsalts 1. Diffusion –when the concentration of minerals salts in the soil solution is higher than that in the root hair cell. 2. Active transport –when the concentration of ions in the soil solution is lower than that in the root hair cell sap. 3. The energy comes from cellular respiration in the root hair cells
  • 43.
    Adaptations of theroot hair cell Feature Adaptation 1 Long and narrow Increases SA:V, thus increasing rate of absorption of water and mineral salts 2 Has cell surface membrane Partially permeable Maintains high conc. of sugars, amino acids and salts in cell sap. Results in lower water potential than soil solution so water can enter by osmosis 3 Is living Able to provide energy for active transport of ions into cell 4 Has protein transporters Able to transport specific mineral ions into the cell.
  • 44.
    2. Up thestem a. Root pressure • Root cells actively pump inorganic ions into the xylem and the root endodermis holds the ions there. • As ions accumulate in the xylem, water enters by osmosis, pushing the xylem sap upward ahead of it. • This force, called root pressure, can push xylem sap up to a few metres. • Root pressure is not enough to bring water up all trees.
  • 45.
    2. Up thestem b. Capillary action - If water is present in a narrow (capillary) tube, forces of attraction exist between: - Water molecules - Water molecules and surface of the tube - Causes water to move up the tubes - Effect is called capillary action - Cannot account for water rising up a tall tree
  • 46.
    Up the stem c.Transpiration pull - Transpiration: Loss of water vapours from aerial parts of plant, especially through stomata of leaves - Transpiration pull: Suction force caused by transpiration - Main factor that causes water to move up the xylem - Transpiration stream: Stream of water moving up
  • 53.
    Why is transpiration important? •Draws water and mineral salts from the roots to the stems and the leaves. • Evaporation of water from the cells in the leaves removes latent heat of vaporisation, so the plant is cooled. • Water transported to the leaves is used for photosynthesis and maintaining the turgidity of the leaf cells.
  • 54.
    ENVIRONMENTAL FACTORS THAT AFFECTTRANSPIRATION 1. Temperature of air 2. Air humidity 3. Light intensity 4. Wind/air movement 5. Carbon dioxide concentration
  • 55.
    1. Temperature ofair • Higher temperatures increases the rate of evaporation • The higher the temperature, the greater the rate of transpiration 30 T degrees Stomata closed
  • 56.
    2. Air Humidity •Air inside leaf is saturated with water vapour • Increasing the humidity of the air will decrease the water vapour concentration gradient between the leaf and the atmosphere, therefore decreasing the rate of transpiration • The lower the humidity, the faster the rate of transpiration T Humidity
  • 57.
    3. Light Intensity •When light intensity is increases, guard cells become turgid. • The stomata opens, increasing the rate of transpiration. • When light intensity is reduced, the stomata closes. • In greater the light intensity, the greater the rate of transpiration Stomata closed T
  • 58.
    4. Wind/air movement •Blows water vapour away at the surface of leaves • Increases concentration gradient between water vapour in the leaf and outside the leaf • This would increase transpiration • When the air is still, transpiration reduces or stops • The stronger the wind, the faster the rate of transpiration T Wind
  • 59.
    5. Carbon dioxide concentration •When carbon dioxide concentration in the intercellular spaces of the leaf falls below a critical concentration, the stomata opens. This increases transpiration. • An increase in carbon dioxide concentration decreases the rate of transpiration. T Co2 concentration
  • 60.
    Wilting • Turgor pressureof mesophyll cells supports the leaf and keep it firm and spread out widely to absorb sunlight for photosynthesis. • In strong sunlight, when the rate of transpiration exceeds the rate of absorption of water by the roots, the cells lose their turgor, become flaccid and the plant wilts. • Wilting also occurs in the soft stems of certain plants in which the stem mesophyll cells lose water. • If rate of transpiration > rate of water absorption, cells become flaccid and plant wilts • Advantages: Reduces rate of transpiration and thus, reduces water loss • Disadvantage: Stomata are closed, reducing entry of CO2. Rate of photosynthesis decreases
  • 61.
    Plant adaptations • Xerophytes-- Plants that live in dry conditions • Adapted to preventing water loss and storing water • Hydrophytes – Water plants • Fully submerged plants adapted to receiving more sunlight • Partially submerged plants adapted to float • Floating plants adapted to float and compete for sunlight
  • 62.
    Xerophytes Mechanism Adaptation Limit waterloss Waxy stomata – Reduces water loss by transpiration Few stomata – Reduces transpiration rate Sunken stomata – hairs of grooves trap water vapour that diffuses out. Increases humidity around stomata, therefore reducing transpiration Reduced leaf size – Reduces exposed surface area Curled leaves – Reduces exposed surface area Water storage Succulent leaves Succulent stems Fleshy tubers
  • 63.
    Hydrophytes Mechanism Adaptation - Thin/nocuticle. -Since cuticle is to prevent water loss, there is less need for cuticle Large intercellular air spaces – aids buoyancy Abundant stomata - No need to reduce water loss - Maximise gaseous exchange
  • 64.
    Using a potometer 1.Insert plant into cork with hole 2. Smear opening with petroleum jelly – makes the apparatus airtight 3. Open tap to fill tube with water 4. As plant transpires, water moves to replace water lost in the plant. Bubble moves along capillary tube
  • 65.
    The basic designof a potometer It consists of: *'''A length of capillary tube''‘ An air bubble is introduced to the capillary. As water is taken up by the plant, the bubble moves and its length of movement is measured by the scale attached with capillary tube . The distance the bubble travels in a given time is determined by the rate of transpiration by the plant. *''' A reservoir'''. By turning the tap on the reservoir, the position of the bubble can be set at the start of the experiment. Some designs of potometer use a syringe instead of a funnel with a tap. • '''A tube for holding the shoot'''. • In the diagram the shoot is held in place by inserting a rubber bung in the tube. The hole in the bung through which the shoot passes must be thoroughly greased with petroleum jelly to keep it airtight.
  • 66.
    Setting up: # Cuta ''leafy'' shoot from a plant (e.g. Pelargonium) and plunge its base into water (try not to get any water on the leaves). This prevents the xylem from taking up any air. #Back in the laboratory, put the stem into a large sink full of water and carefully trim the shoot again, by cutting off the bottom '''under water''' with a sharp razor blade. Keep the leaves out of the water. #Immerse the whole of the potometer into the sink. Move it about until all the air bubbles come out. #Put the shoot stem into the bung, grease the joint with plenty of petroleum jelly, then put the bung into the potometer. #Make sure the tap is closed, then lift the whole ensemble out of the water. #Leave the end of the capillary tube out of the water until an air bubble forms then put the end into a beaker of water.
  • 67.
    Using a potometer= Allowthe bubble time to go around the corner and start at the beginning of the millimeter scale. Then measure how far the bubble moves in a given period of time. Repeat under different conditions and compare. The usual conditions to try are placing the plant in a bright light, placing it by a fan, and placing it in a humid atmosphere. If the surface area (both sides) of the leaves are measured then it is possible to compare the transpiration rates of different species of plant.
  • 68.
    'Limitations of a potometer' #Introducing the air bubble is not easy. # The leafy shoot may not remain fully alive for as long as wanted. # Any changes in the outside air temperature may affect the position of the air bubble in the capillary tube.
  • 76.
    Experiment to demonstrateTranspiration by Four-Leaf Experiment: Requirements: Four leaves, Vaseline and a string. Experiment: To demonstrate the transpiration from the leaf surface, four banyan leaves are taken. Both the surfaces of the A leaf, lower surface (with stomata) of B leaf, upper surface (without stomata) of C leaf are vaselined. The Vaseline is not applied on the D leaf. Now, as shown in the figure the leaves are hanged so that they may transpire freely.
  • 77.
    Observation and Explanation: Whenthe observations are taken after a day or two, they are as follows — the A leaf, which is vaselined on its both the surfaces, looks fresh and green, as no surface transpires. The B leaf is vaselined on its lower surface (with stomata), and transpiration takes place only from the upper surface which is negligible. This leaf also remains turgid and green like the A leaf. If few stomata are present on the upper surface of the leaf, then it shrivels to some extent. The C leaf is vaselined on its upper surface, which contains less number of stomata or no stomata. The transpiration takes place from the lower stomatal surface, and the leaf shrivels to a large extent. The D leaf is not vaselined and both the surfaces transpire freely releasing much water. The leaf wilts completely in this case. This experiment proves that the rate of stomatal transpiration is fairly higher than the cuticular transpiration.
  • 78.
    Observation and Explanation: Whenthe observations are taken after a day or two, they are as follows — the A leaf, which is vaselined on its both the surfaces, looks fresh and green, as no surface transpires. The B leaf is vaselined on its lower surface (with stomata), and transpiration takes place only from the upper surface which is negligible. This leaf also remains turgid and green like the A leaf. If few stomata are present on the upper surface of the leaf, then it shrivels to some extent. The C leaf is vaselined on its upper surface, which contains less number of stomata or no stomata. The transpiration takes place from the lower stomatal surface, and the leaf shrivels to a large extent.
  • 79.
    Experiment to demonstratethat there is a loss in the total weight of plant due to transpiration: Requirements: 1. Spring balance (2), two leaves of almost equal size, test tube (2), water, vaseline and stand. Method: 1. Take two test tubes filled with water and close their mouth with a cork having a hole. 2. Insert the petiole of both the leaves, one in each test tube, and note that it is dipped in water. 3. Apply vaseline on both the surfaces of leaf ‘B’. 4. Connect both the spring balances with the stand and hang both the tubes on the hook of spring balances (Fig. 27).
  • 80.
    5. Make boththe corks air-tight by applying vaseline. 6. Note the weight of both the tubes. 7. Put the whole apparatus in light and wait for a few hours. Note the weight of both the tubes again.
  • 81.
    It is observedthat there is a clear loss in weight of test tube having leaf ‘A’ and there is no change in weight in leaf ‘B’. Results: Loss in the weight of leaf ‘A’ indicates that this is due to the process of transpiration because the leaf is continuously transpiring the water vapours. But on both the surfaces of leaf ‘B’ vaseline has been applied and so the leaf is not transpiring and so there is no change in its weight. These results clearly indicate that during the transpiration there is a loss in the total weight of the plant.Rate of transpiration can be calculated as shown below Rate of transpiration= loss in mass/time taken g/h
  • 82.
    Experiment to demonstratethe water- lifting power of transpiration process: Requirements: Beaker, water, mercury, stand, capillary tube, vaseline, cork, plant twig, oil cloth. Method: 1. Take some amount of mercury in the beaker and invert a wide-mouthed capillary tube over it. 2. Fill the capillary tube with water. 3. Insert the plant twig into the hole of the cork in such a way so that its cut end is dipped in the water. 4. Apply the vaseline on the cork and hole to make it air-tight (To make the cork region air-tight oil cloth may also be used instead of vaseline). 5. Keep the whole apparatus in sun. 6. Note the mercury level in the capillary tube and wait for some time.
  • 83.
    Observations: Mercury level risesin the capillary tube(Fig.16).
  • 84.
    Results: Mercury level risesin the capillary tube because of the pull or suction exerted by the transpiration process. Aerial parts of the plants are continuously evaporating water because of transpiration process. To compensate this loss the water is absorbed by the plant and lifted. So, the space in the capillary tube, which was first occupied by this absorbed water, is now occupied by the mercury. This demonstrates the water-lifting power of the transpiration process.
  • 85.
  • 86.
    WILTING Wilting is theloss of rigidity of non-woody parts of plants. This occurs when the turgor pressure in non-lignified plant cells falls towards zero, as a result of diminished water in the cells.The cells become flaccid. The rate of loss of water from the plant is greater than the absorption of water in the plant. Lower water availability may result from: • drought conditions, where the soil moisture drops below conditions most favorable for plant functioning; • the temperature falls to the point where the plant's vascular system cannot function; • high salinity, which causes water to diffuse from the plant cells and induce shrinkage; • saturated soil conditions, where roots are unable to obtain sufficient oxygen for cellular respiration, and so are unable to transport water into the plant; or • bacteria or fungi that clog the plant's vascular system.
  • 87.
    Advantages and Disadvantagesof wilting Advantage: with the guard cells not turgid, the stomata close and the rate of water loss is reduced. Rate of transpiration is reduced because the leaf folds up that is reducing the surface that is exposed to sunlight. Disadvantage: Rate of photosynthesis reduced because water becomes the limiting factor .Also as the stomata are closed,gas exchange in the leaves slows, and therefore so does photosynthesis.

Editor's Notes

  • #10 plasmodesmata
  • #21 How are the cells different?