ch 6,8

Carbon dioxide + water → glucose + oxygen (in the presence of light and chlorophyll).

What is the word equation for photosynthesis?

Light energy is not a substance; it is a form of energy required for the reaction.

Why is light energy not considered a raw material for photosynthesis?

Nitrogen is needed to make amino acids, which are used to synthesize proteins.

What is the role of nitrogen in plants?

Magnesium.

Which mineral is essential for chlorophyll synthesis?

They remain orange-brown because photosynthesis does not occur, and no starch is produced.

What happens to leaves without chlorophyll during a starch test?

To ensure any existing starch is used up, so results reflect starch produced during the experiment only.

Why are plants destarched before photosynthesis experiments?

As light intensity increases, the rate of photosynthesis increases, until another factor becomes limiting.

How does light intensity affect the rate of photosynthesis?

Light intensity, carbon dioxide concentration, and temperature.

What are the three main limiting factors of photosynthesis?

Plants need only a small amount for photosynthesis compared to the water lost through transpiration.

Why is water not considered a limiting factor in photosynthesis?

To regulate the opening and closing of stomata for gas exchange.

What is the primary function of guard cells?

To transport food materials (sucrose and amino acids) from photosynthetic regions to other parts of the plant.

What is the role of phloem in plants?

By osmosis, as the water potential in the soil is higher than that in the root hair cells.

How do root hair cells absorb water?

Lignin is a substance that thickens and strengthens xylem walls, helping them withstand water pressure.

What is lignin, and what is its role in the xylem?

The continuous movement of water through the xylem from roots to leaves.

What is the transpiration stream?

More water evaporates from leaves than is available for absorption by roots.

What is the primary cause of wilting in plants?

To allow the exchange of gases (intake of CO₂ and release of O₂) for photosynthesis.

What is the function of stomata during the day?

It absorbs carbon dioxide to test its necessity for photosynthesis.

What does sodium hydroxide do in photosynthesis experiments?

The rate increases until enzymes denature at high temperatures, reducing the rate.

How do increasing temperatures affect the rate of photosynthesis?

How do you investigate the need for carbon dioxide in photosynthesis?

• Destarch two plants – Place them in the dark for 24 hours.

• Place one plant near sodium hydroxide – This absorbs carbon dioxide.

• Place the other plant near water – This acts as a control, as water does not absorb CO₂.

• Expose both plants to sunlight – Allow photosynthesis to occur in the control plant.

• Test a leaf from each plant for starch –

  • The plant near sodium hydroxide will remain orange-brown (no CO₂, no photosynthesis).

  • The plant near water will turn blue-black (photosynthesis occurred).

Carbon dioxide is taken in, and oxygen is released.

What is the primary gas exchanged during photosynthesis?

Large surface area, thin structure, and presence of chloroplasts in palisade mesophyll cells.

What adaptations help the leaf maximize photosynthesis?

They allow the diffusion of gases (CO₂ and O₂) within the leaf.

What is the significance of air spaces in spongy mesophyll?

Through the phloem via translocation.

How is sucrose transported in plants?

Increased wind speed removes water vapor near the leaf, increasing the rate of transpiration.

How can wind speed influence transpiration?

To allow sunlight to pass through to the photosynthetic tissues below.

Why is the upper epidermis transparent?

Oxygen gas being released during photosynthesis.

What does the presence of bubbles in a pondweed experiment indicate?

It transports water, a raw material for photosynthesis, to the leaves.

Why is the xylem important for photosynthesis?

Blue-black.

What color does iodine turn in the presence of starch?

The rate of photosynthesis increases only as light intensity increases.

What happens when light is a limiting factor in photosynthesis?

It decreases transpiration because the air is already saturated with water vapor.

How does high humidity affect transpiration?

leaves.

Photosynthesis primarily occurs in the __________ of the plant.

C₆H₁₂O₆.

The chemical formula for glucose is __________.

chlorophyll.

Light energy is captured by __________ in chloroplasts.

transpiration.

The process by which plants lose water vapor is called __________.

water.

In photosynthesis, oxygen is produced as a by-product from the splitting of __________ molecules.

light-dependent.

The __________ stage of photosynthesis converts light energy into chemical energy.

cannot.

In the absence of light, photosynthesis __________ occurs.

stomata.

Carbon dioxide enters the leaf through small openings called __________.

• Boil the leaf in water – This kills the cells and breaks down the cell membranes.

• Soak the leaf in hot ethanol – Removes chlorophyll, making it easier to see the iodine color change.

• Rinse the leaf in warm water – Softens the leaf after ethanol treatment.

• Place the leaf on a white tile – Ensures a clear background for observing the test.

• Add iodine solution – Tests for starch. Areas with starch turn blue-black; areas without starch remain orange-brown.

What are the steps to test a leaf for starch in a photosynthesis investigation?

• Destarch the plant – Place it in the dark for 24 hours to remove existing starch.

• Cover part of a leaf with aluminum foil – Blocks light from reaching that area.

• Expose the plant to sunlight – Place it in sunlight for a few hours.

• Remove and test the leaf for starch – Follow the starch test procedure.

  • Observation: The covered area remains orange-brown, while the exposed area turns blue-black.

What are the steps to investigate the effect of light on photosynthesis?