Plant Form and Function Study Guide

Environmental Energy Mismatch Case-study

• Caribou migration triggered by day-length• ↑ temp. has sped up plant sprouting in the spring• Now plant nutrition and digestibility have peaked

before the arrival of caribou• There is a mismatch in timing between new plant

growth and caribou birthing• Without adequate nutrition for nursing, production

of offspring has declined 75% since 1993

Simplified Carbon-Cycle 1. Which arrow (I or II) is photosynthesis? Which is respiration?

2. When a plant grows and gains mass, where does that mass come from?

3. What would happen to a plant’s mass if it was kept in the dark for two days? What chemical reaction is responsible? Where would the mass go?

Simplified Carbon-Cycle 1. I is photosynthesis and II is cellular respiration

2. When a plant grows, mass is added as CO2 is assimilated during photosynthesis

3. If a plant was kept in the dark, it would continue to perform cellular respiration (to maintain homeostasis), which would breakdown stored starch/sugar and release CO2

gas, the plant would lose mass (and photosynthesis could not be performed)

Predict how the following treatments would affect the rate of germination? Justify each prediction:

1. Temperature: cold, warm, boiling2. Environment with/without oxygen3. Environment with/without light

During germination, cellular respiration recycles ATP that is required for cell-division (growth), no photosynthesis occurs until the first leaves (and chlorophyll) are produced.

1. Increasing temperature should increase the rate of the chemical reaction of cellular respiration, and thus increase the rate of germination; however, boiling will result in enzymes denaturing and will thus kill the embryo.

2. Cellular respiration requires oxygen, and thus it can not occur, and germination would thus cease in an environment without oxygen.

3. Germination involves cellular respiration, not photosynthesis, and thus does not require light.

1. What is the effect of the plant hormone ethylene on fruit ripening?

2. How does fruit change as it ripens?

3. What is the mechanism behind ripening?

4. Why does fruit ripen faster if placed in a paper bag?

1. What is the effect of the plant hormone ethylene on fruit ripening? Ethylene appears to stimulate fruit ripening

2. How does fruit change as it ripens? Acids neutralized, starch turned to sugars, chlorophyll breaks down, fruit becomes soft and more fragrant

3. What is the mechanism behind ripening? Ethylene appears to act as a signal (hormone) molecule that activates a series of enzymes

4. Why does fruit ripen faster if placed in a paper bag? A paper bag likely traps the ethylene, allowing it to build up to a larger concentration

1. When is the embryo only performing cellular respiration?

2. Why does it need to do this?

3. Why does the stem need to elongate?

4. What is needed for chlorophyll production and why?

5. When does photosynthesis start?

Stem elongation to get plant above ground

When exposed to light, chlorophyll is produced and photosynthesis can start (respiration continues)

Cellular respiration for growth (↑ cell #) using starch/oils stored in seed.

Predict the effect of the loss of decomposers (bacteria and fungi) on the chemical cycling of matter in ecosystems.

Without decomposers (bacteria and fungi) dead organic material (detritus) would not be broken down and the nutrients locked away in this material would not be released into the environment for new plant growth – plant growth would likely decrease.

Data on date of emergence of butterflies from the chrysalis:

1. What has been the trend in when butterflies emerge from 1840 to 2010?2. What has been the trend in mean April – October temperatures from 1940

to 210?3. Suggest how these two data sets are connected:

Data on date of emergence of butterflies from the chrysalis:

1. Now, butterflies emerge earlier than they did historically (circa 1940).2. The mean temperature has increased from 1940 to 2010.3. An increase in temperature likely speeds up the process of metamorphosis,

allowing butterflies to emerge earlier than they did historically.

As ground-cover (shading vegetation) is reduced, soil temperature would be expected to increase during warm, sunny days because more sunlight would reach the soil’s surface.

Fire would be expected to clear away vegetation and thus result in warmer soil surfaces.

Predict the effect of ground-cover (shading by vegetation) on soil temperature. Describe what a graph of these two variables would look like. Explain how fire in an environment could affect soil temperature.

Soil

Tem

per

atu

re (

⁰C)

Ground-cover (vegetation)

Describe & explain the relationship between

the variables from 0 – 60% open stomata.

Do the same for >60% open stomata.

For which type of plant would you expect to find:

• Stomata on both top and bottom leaf surfaces

• No stomata

• Stomata only on the top Justify your selection:

For which type of plant would you expect to find:

• Stomata on both top and bottom leaf surfaces

Emergent plant such as the cattails because both

surfaces are exposed to air and the stomata are

necessary for gas-exchange but also help to limit

water-loss due to transpiration.

• No stomata The aquatic plant will do gas

exchange via diffusion of gases from water

through the entire leaf surface area. Water is also

not limiting because the plant is submerged.

• Stomata only on the top The water lily only has its

upper surface exposed to air. Here it will want to

control water-loss via stomata regulation. The

bottom surface is exposed to water, plant does

not have to control for water loss here.

Why do many terrestrial plants have

stomata only on the bottom of their

leaves (or more on the bottom than top)?

Why do many terrestrial plants have stomata

only on the bottom of their leaves (or more

on the bottom than top)? The top of the

leaves are exposed to more sunlight, which

would speed evaporation from stomata.

Concentrating stomata on the leaf bottoms

helps to slow water loss via transpiration.

1. Show a graph of the relationship

between temperature and the rate

of transpiration (make sure you

label your axes)

2. Discuss the mechanism by which

temperature effects the rate of

transpiration:

As temp. ↑, kinetic

energy of molecules ↑,

thus the speed of

diffusion (evaporation of

water from stomata

openings) will increase.

At a certain temp. the

rate will level off

because other factors

now limit the rate of

transpiration.

1. Show a graph of the relationship

between relative humidity and the

rate of transpiration (make sure

you label your axes and note that

relative humidity runs on a scale

from 0 to 100%)

2. Discuss the mechanism by which

humidity effects the rate of

transpiration:

As relative humidity ↑, transpiration rate ↓,

because as humidity ↑, the gradient in Ψ

between the leaf and the air ↓, thus water loss ↓.

As % open stomata ↑ from 0 to 60, so does the

rate of transpiration because with more stomata

open there is ↑ diffusion between the leaf and the

environment. Above 60%, there is no change in

the rate of transpiration because another factor

becomes limiting (i.e. rate of water movement,

humidity, etc.).

1. Show a graph of the relationship

between light intensity and the rate

of transpiration (make sure you

label your axes)

2. Discuss the mechanism by which

light intensity effects the rate of

transpiration:

The effect of light on the rate of transpiration

Light is needed to drive the process of photosynthesis. As light intensity increases, so does the rate of photosynthesis until light is no longer limiting to the reaction.

As the rate of photosynthesis increases, the demand for CO2 also increases, and more stomata must open to meet the demand.

1. What is the effect of wind on the

rate of transpiration?

2. Discuss the mechanism by which

wind effects the rate of

transpiration:

Boundary layer of high humidity,

difference in Ψ inside and

outside the leaf is ↓, so

transpiration rate ↓

Wind blows away

boundary layer

Difference in Ψ (or osmotic

potential) inside and outside the leaf ↑, so transpiration rate ↑