Plant Transpiration Lab

Data Table

 

	Normal	With Fan	With Heater	With Lamp
Arrowhead	3.6	7.5	6.6	4.0
Coleus	0.9	6.0	3.9	3.0
Devil’s Ivy	2.9	4.6	4.1	3.0
Dieffenbachia	4.1	7.7	6.0	3.9
English Ivy	1.8	5.1	3.2	2.1
Geranium	1.2	4.7	5.8	2.4
Rubber plant	4.9	8.4	6.8	4.3
Weeping Fig	3.3	6.1	4.9	2.5
Zebra Plant	4.2	7.6	6.1	3.2

Calculations 


The numerical effect of the wind (fan) on each plant
 

Arrowhead: 7.5-3.6 = +3.9
Coleus: 6.0-0.9 = +5.1
Devil's Ivy: 4.6-2.9 = +1.7
Dieffenbachia: 7.7-4.1 = +3.6
English Ivy: 5.1-1.8 = +3.3
Geranium: 4.7-1.2 = +3.5
Rubber Plant: 8.4-4.9 = +3.5
Weeping Fig: 6.1-3.3 = +2.8
Zebra Plant: 7.6-4.2 = +3.4

Average: +3.42 (The wind had a positive effect, increasing the average transpiration rate of the plants by 3.42)



The numerical effect of the heat (heater)

Arrowhead: 6.6-3.6 = +3.0
Coleus: 3.9-0.9 = +3.0
Devil's Ivy: 4.1-2.9 = +1.2
Dieffenbachia: 6.0-4.1 = +1.9
English Ivy: 3.2-1.8 = +1.4
Geranium: 5.8-1.2 = +4.6
Rubber Plant: 6.8-4.9 = +1.9
Weeping Fig: 4.9-3.3 = +1.6
Zebra Plant: 6.1-4.2 = +1.9

Average: +2.28 (The wind had a positive effect, increasing the average transpiration rate of the plants by 2.28)


The numerical effect of light (lamp)

Arrowhead: 4.0-3.6 = +0.4
Coleus: 3.0-0.9 = +2.1
Devil's Ivy: 3.0-2.9 = +0.1
Dieffenbachia: 3.9-4.1= -0.2
English Ivy: 2.1-1.8 = +0.3
Geranium: 2.4-1.2 = +1.2
Rubber Plant: 4.3-4.9 = -0.6
Weeping Fig: 2.5-3.3 = -0.8
Zebra Plant: 3.2-4.2 = -1.0

Average: +0.17 (the light had a marginal positive effect, increasing the average transpiration rate of the plants by 0.17)


Therefore, the wind, followed by heat and light, had the biggest impact on the plants' transpiration rate.  

Journal analysis questions

1.     Describe the process of transpiration in vascular plants.

 

In vascular plants, water is absorbed through the roots and carried upward through the stem to the leaves. Some of the water absorbed by a plant's roots is used for photosynthesis, but much is lost to the environment by evaporation through stomata.  This process is called transpiration.

 

2.     Describe any experimental controls used in the Investigation.

 

In a laboratory, a plant's transpiration rate can be measured using a potometer.

To measure transpiration rate, a plant sprig is mounted on the potometer and the burette and pipette are filled with water. Over time the plant will transpire and absorb water through its stem. The potometer is constructed in such a way that the plant's water source is the pipette, therefore the amount of water transpired over time can be determined by reading the water level in the pipette after time has passed. The water supply in the pipette can be replenished from the water supply in the burette by releasing the pinch clamp.

 

3.     What environmental factors that you tested increased the rate of transpiration? Was the rate of transpiration increased for all plants tested?

 

Wind and heat increased the rate of transpiration for all plants tested.

Light, however, increased the transpiration rate for some plants, and decreased the rate for others.

 

4.     Did any of the environmental factors (heat, light, or wind) increase the transpiration rate more than the others? Why?

 

Wind increased the transpiration rate more than heat and light did.

This is somewhat related to the relative humidity of the air, in that as water transpires from a leaf, the water saturates the air surrounding the leaf. If there is no wind, the air around the leaf may not move very much, raising the humidity of the air around the leaf. Wind will move the air around, with the result that the more saturated air close to the leaf is replaced by drier air.

 

 

5.     Which species of plants that you tested had the highest transpiration rates? Why do you think different species of plants transpire at different rates?

 

Rubber plant showed the highest transpiration rate. This is primarily due to its leaves with a bigger surface area. Varying transpiration rates according to different species are the result of adaptation to climate. Some plants which grow in arid regions, such as cacti and succulents, conserve precious water by transpiring less water than other plants.

 

6.     Suppose you coated the leaves of a plant with petroleum jelly. How would the plant's rate of transpiration be affected?

 

As petroleum jelly tends to hinder water from evaporating, the transpiration rate will drop abruptly.

 

7.     Of what value to a plant is the ability to lose water through transpiration?

 

Transpiration cools plants, changes osmotic pressure of cells, and enables mass flow of mineral nutrients and water from roots to shoots.

 

 

 

 

 

Auxins, Abscisic Acid and Ethylene

Auxins derive their name from the Greek word αυξειν ("to grow/increase"). Auxin participates in phototropism, geotropism, hydrotropism and other developmental changes. The uneven distribution of auxin, due to environmental cues, such as unidirectional light or gravity force, results in uneven plant tissue growth. Auxin generally governs the form and shape of plant body, direction and strength of growth of all organs, and their mutual interaction.

 

 

<Native auxins>

 

 

Funtions of auxins:

• Stimulates cell elongation
• Stimulates cell division in the cambium and, in combination with cytokinins in tissue culture
• Stimulates differentiation of phloem and xylem
• Stimulates root initiation on stem cuttings and lateral root development in tissue culture
• Mediates the tropistic response of bending in response to gravity and light
• The auxin supply from the apical bud suppresses growth of lateral buds
• Delays leaf senescence
• Can inhibit or promote (via ethylene stimulation) leaf and fruit abscission
• Can induce fruit setting and growth in some plants
• Involved in assimilate movement toward auxin possibly by an effect on phloem transport
• Delays fruit ripening
• Promotes flowering in Bromeliads
• Stimulates growth of flower parts
• Promotes (via ethylene production) femaleness in dioecious flowers
• Stimulates the production of ethylene at high concentrations

 

 

 

 

 

 

Abscisic acid is a single compound unlike auxins. Abscisic acid owes its names to its role in the abscission of plant leaves. In preparation for winter, ABA is produced in terminal buds. This slows plant growth and directs leaf primordia to develop scales to protect the dormant buds during the cold season. ABA also inhibits the division of cells in the vascular cambium, adjusting to cold conditions in the winter by suspending primary and secondary growth.

 

 

Functions of Abscisic acid:

• Stimulates the closure of stomata (water stress brings about an increase in ABA synthesis).
• Inhibits shoot growth but will not have as much affect on roots or may even promote growth of roots.
• Induces seeds to synthesize storage proteins.
• Inhibits the affect of gibberellins on stimulating de novo synthesis of a-amylase.
• Has some effect on induction and maintanance of dormancy.
• Induces gene transcription especially for proteinase inhibitors in response to wounding which may explain an apparent role in pathogen defense.

 

Ethylene, unlike the rest of the plant hormone compounds, is a gaseous hormone. Like abscisic acid, it is the only member of its class. Of all the known plant growth substance, ethylene has the simplest structure. It is produced in all higher plants and is usually associated with fruit ripening and the tripple response.

 

H₂C=CH₂

FUNCTIONS OF ETHYLENE:

• Stimulates the release of dormancy.
• Stimulates shoot and root growth and differentiation (triple response)
• May have a role in adventitious root formation.
• Stimulates leaf and fruit abscission.
• Stimulates Bromiliad flower induction.
• Induction of femaleness in dioecious flowers.
• Stimulates flower opening.
• Stimulates flower and leaf senescence.
• Stimulates fruit ripening.