Unit 3 Environmental Adaptations for Plants

What do stomata allow for?

Entrance of carbon dioxide into the cell, exit of oxygen from the cell, and evaporation of water out of the leaves 

How will plants conserve water on hot, dry days or in hot, dry climates?

By closing their stomata

What does the closing of plants’ stomata cause a decrease in?

CO₂ concentration

What continues to happen when plants’ stomata are closed?

Light-dependent reactions

What builds up when plants’ stomata are closed?

Oxygen

What occurs in C3 plants?

Photorespiration

What are C3 plants?

Platns who use CO₂ to make a 3-C compound as the first step of the Calvin Cycle

What will happen as oxygen builds up from the closing of stomata?

Rubisco will add oxygen to RuBP instead of carbon dioxide 

What happens after the product of RuBP and oxygen splits?

2-carbon piece will be exported out of the chloroplast

What breaks down the two carbon compound into carbon dioxide after it’s exported out of the chloroplast?

Mitochondria and peroxisomes

Why is photorespiration bad for plants?

Lots of energy is used and no sugar and oxygen is produced

Why is photorespiration thought to be an evolutionary throwback?

Counterproductive for the plant as it drains carbon away from the Calvin cycle

When did rubisco likely evolve?

When there was little oxygen in the atmosphere

What is alternative pathway to making sugars?

C4 pathways 

Why do plants in hot, arid climates use C4 pathways?

To maximize photorespiration

What are C4 pathways important in?

Agriculture including corn, sugarcane, and grasses

What must C4 plants have?

Unique leaf anatomy

What are the two types of photosynthetic cells C4 plants must have?

Bundle sheath and mesophyll cells

What are bundle sheath cells tightly packed around?

Veins

What are mesophyll cells tightly packed and organized around?

Bundle sheath cells

What are the only cells C4 plants have that are capable of photosynthesis?

Mesophyll cells

What do the two different photosynthetic cells of C4 pathways allow for?

Separation of the light-dependent and light-independent reactions of photosynthesis

What occurs in the mesophyll cells of C4 photosynthesis?

Light-dependent reactions

What occurs in the bundle sheath cells of C4 photosynthesis?

Light-independent reactions

What does the separation of light-dependent and light-independent reactions in C4 photosynthesis hide?

Oxygen in the mesophyll cells from rubisco in the bundle sheath cells 

What is CO₂ fixed into mesophyll cells?

PEP

What enzyme helps fix CO₂ in mesophyll cells into PEP?

PEP carboxylase

What is made when CO₂ is fixed into PEP?

4-C compound called oxaloacetate

What does PEP carboxylase have for CO₂?

A higher affinity

PEP carboxylase will not cheat even though O₂ levels are higher than CO₂ levels.

True

What is oxaloacetate shuttled through?

Plasmodesmata

What is oxaloacetate broken down into?

3-C pyruvate and CO₂

What is CO₂ given off to in C4 pathways?

Rubisco

What is the leftover 3-C pyruvate recycled into in C4 pathways?

PEP by the use of ATP

What is the difference between all other light-independent reactions and the light-independent reactions of C4 photosynthesis?

Location in which sugar is made

What is another alternate adaptation to arid conditions?

CAM pathways

What are three examples of CAM plants?

Succulents, cacti, and pineapples

When is the only time CAM plants open their stomata?

At night

What do CAM plants take up at night?

CO₂

What do CAM plants use PEP carboxylase to fix CO₂ into?

Organic acid molecules 

What do CAM plants store excess organic acids in?

Vacuoles in mesophyll cells

What will the organic acids of CAM plants do during the day?

Release CO₂ to be used in a normal Calvin cycle

When will the organic acids of CAM plants release CO₂ to be used in a normal Calvin cycle?

During the day when light-dependent reactions make ATP and NADPH to power the Calvin cycle

What is the difference between all other light-independent reactions and the light-independent reactions of CAM photosynthesis?

Sugars are made at night

What percent of the organic material made in photosynthesis is used for cell respiration?

50%

What does the rest of the plant depend on?

Products made by the “green cells”

What will the leaves transport to other areas via veins?

Carbohydrates

Where is excess sugar stored in within plants?

Roots, tubers, seeds, and fruits

How many tons of carbohydrates does photosynthesis account for on a global scale?

160 billion metric tons