A. Transpiration

Transpiration: A process in plants in which wateris lost in the form of water vapourthrough evaporation from the surface of the leaves.

If too much water is evaporatedfrom the plant, the cells of the plants will lose their tungar pressure and wilt. If this conditon persists the plant will die.

Aim: to study transpiration in plants.Material: balsam plant, oil, dry cobalt chloride paperApparatus: 500ml beaker, bell jar.Steps:

Experiment 2.1: to study the transpiration in plants

Bell jarOil layerWater

Balsam plant

Procedure:1. Arrangement of apparatus was prepared.2. Set A and set B are left in the sunlight fro 30 minutes3. The inside wall of the bell jar was observed at the end of the activities. Liquid that was formed is tested with dry cobalt chloride paper.

Observation:1. Drops of liquid have formed on the inside wall of bell jar B.2. The dry cobalt chloride paper change colour from blue to red.

Analysis:1. Set A acts as a control experiment2. A layer of oil is added to the surface water to prevent water in the beaker from evaporating.3. Plants release water through the pores of the stomata on the leaves to environment through the transpiration.

Conclusion:Plants release water from leaves through transpiration.

Most water vapour is lost through stomata of leaves.

Stomata:Pores or opening on the surface of

leaves.

Stomata:a. A lot can be found under surface of leavesb. Have guard cells to control the loss of water from plants.c. The pore size of the stomata is control by guard cellsd. A lot of water will be lost if the pore size of the stomata is large

Guard cell

Pore of stomaNucleus

Stomata pore under a microscope

Aim: to observe leaf stomata under a microscope.Material: leaves, waterApparatus: small knife, forceps, slides, glass cover, microscope.

Procedure:1. A thin portion of undersurface of a leaf is cut out with a small knife2. The leaf is bent on the portion that is cut. A small part of the leaf surface is taken out with a pair of forceps.3. The layer of the leaf then placed on a drop of water on a slide is then covered with glass cover.4. The stomata of the leaf are observed under a microscope

Experiment 2.2

Stomata pore under a leaf

Observation :

Stomata

Conclusion:Leaf stomata are openings on the surface of a leaf

Factors affecting the rate of transpiration

i. Temperature:Temperature increase,transpiration rate increase.

ii. Light intensityHigh light intensity rises the rate of transpiration

iii. Humidity (air moisture)Dry air increase therate of transpiration

iv. Wind Moving air rises the rate of transpiration.

Aim: to study the factors affecting transpiration rate.Material: leaves shoot, cotton, vaseline, rubber tube thin wire.Apparatus: potometer, knife, stopwatch, basin rubber tube

Experiment 2.3

Hypothesis: the higher the temperature, the higher the rate of transpiration

Variables:a) Kept constant: light intensity/wind speed/air moistureb) manipulated: temperaturec) Responds: transpiration rate

Rubber tube

Water reservoir

Ruler

CapillarytubeMeniscus

Screw clip

1. A twig of suitable size is chosen to fit into a rubber tube2. A basin of water is prepared3. The twig is soaked in the basin of water and the plant shoot is cut at an angle 15-20cm in length4. The clip of the potometer is opened for it to be filled with water

Procedure:

5. The end of the plant shoot is quickly put into the rubber tube and the other end of the rubber tube is connected to the potometer6. The joint of the plant shoot to the rubber tube is coiled with thin wires and smeared with vaseline to make the joint airtight7. The screw clip is closed and the apparatus is left until the water, meniscus in the arm of the potometer moves steadily.8. The position of the water meniscus is recorded and the readings are taken every 2 minutes for 20 minutes.9. The result are recorded in a table and a graph is plotted.10. The screw clip is opened and the potometer is refill with water11. The experiment is prepared with the apparatus placed in a hot place.12. Result obtained are recorded in table and a graph is plotted

This experiment is repeated with the test on light intensity, wind and humidity.

Result:

Time Position of meniscusNormal Temperature Light intensity Wind

speedHumidity

0 0 0 0 0 02 10 14 16 12 64 20 28 32 24 126 30 43 48 36 188 40 58 64 48 2410 50 72 80 60 30

Graph of meniscus position against time

0102030405060708090

1 2 3 4 5 6Time

Men

sicu

s po

sitio

n

Light intensityHigh temperatureHigh wind speedNormal condition

High air humidity

Analysis:1. The rate of transpiration increase when: a. temperature higher b. light intensity is higher c. wind speed is higher

2. Transpiration will be decrease when air moisture increase

3. Factors like temperature, light intensity, wind and humidity can be get by using potometer

4. Plants lose water during transpiration through the stomata, cuticle and lenticel.

Conclusion:1. The transpiration rate increase when: a. temperature rises b. light intensity increases c. wind speed increases d. humidity decreases.

The importance of transpiration to a plant

a. Get rid of excess water from plantsb. Cool plants on hot daysc. Transport water and mineral salts from the roots to the whole plant

Transport system in plants consists of

Xylem Transport waterand mineral salts

PhloemTransport food

RootsStems

Leaves

Can be found in

xylem

Phloem

Phloem

Xylem

Phloem

Xylem Xylem

Phloem Leaf tissue

Dicotyledon plant Monocotyledon plant

Dicotyledon plant Monocotyledon plant

Stem tissue

Dicotyledon plant Monocotyledon plant

Root tissue

Phloem

Xylem

Xylem Phloem

Procedure:1. The roots of balsam tree was cleaned2. Few drops of red ink was added into the conical flask which filled of water3. The apparatus is placed in the lab for a day4. A layer of stems, roots and leave was cut5. This sample was placed on the slide and was observed under microscope

Experiment 2.4Aim: To study the transport of water from the roots to the leaves through xylemMaterial: balsam plant, red colored water, red colored pencilApparatus: microscope, slide, glass cover, 500 ml beaker, knife

Observation:

Xylem Phloem

Cross-section of roots

Phloem

Xylem

Cross-section of leaf

Cross-section of stem

LongitudinalCross-section

Phloem Xylem

Analysis:The xylem function to transport water and mineral salts

Conclusion:Water is transport to the leaves through the xylem

Procedure:1. A part of the bark of a stem from hibiscus was cut.2. A little paraffin oil is applied to the cut section part3. The plant is watered everyday4. The plant stem is observed after 2-3 days5. The observation was drawn

Experiment 2.5Aim: To study the transport of the product of photosynthesis (glucose) via the phloemMaterial: hibiscus plant, Apparatus: knife

Cut Upper part become swollen

Before experiment After experiment

lower part become wilted and shrivelled

Analysis:1. Phloem was a part of bark.2. A plant was exposed to the sunlight and watery everyday to enable plants carryout photosynthesis3. A paraffin oil is used to prevent the loss of water from stem tissue4. Swollen is caused by the food accumulates at the top portion near the leaves5. The plants still alive because xylem is not broken.

Conclusion:The product of photosynthesis (glucose) is transported through the phloem to the stem and root