Photosynthesis and Plant Transport Systems

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Questions and Answers

What initiates the loading of sugar into the companion cell?

Pressure gradient from sink to source

Osmosis from the surrounding cells

Diffusion from sieve tube elements

Active transport at the source (correct)

How does sucrose move from companion cells into sieve tube elements?

By osmosis

By active transport

By diffusion (correct)

By facilitated diffusion

What happens to the water potential of the sieve tube element when sucrose enters?

It decreases. (correct)

It fluctuates rapidly.

It increases significantly.

It remains unchanged.

What drives the movement of water into the phloem?

Osmosis due to low water potential Signup and view all the answers

What is the end result of solutes moving to the sink cells?

Solutes increase the water potential at the sink. Signup and view all the answers

Which of the following is NOT an internal factor affecting translocation?

Temperature Signup and view all the answers

What is the main function of photosynthesis in green plants?

To produce organic molecules from sunlight Signup and view all the answers

What byproduct is produced during photosynthesis?

Oxygen Signup and view all the answers

What is produced during the Calvin Cycle?

Glucose Signup and view all the answers

Which of the following statements is true about the light-dependent reactions?

Water is used as a substrate. Signup and view all the answers

What happens to the rate of photosynthesis at CO2 concentrations above 1.0%?

It decreases due to stomata closure. Signup and view all the answers

Which process occurs during the Calvin Cycle?

Carbon dioxide fixation Signup and view all the answers

What are the external factors influencing the rate of photosynthesis?

Light, temperature, and CO2 concentration Signup and view all the answers

Where do the light-dependent reactions of photosynthesis occur?

In the thylakoid membrane Signup and view all the answers

What is the optimum temperature range for photosynthesis?

20 - 35°C Signup and view all the answers

What is the effect of high oxygen concentration on photosynthesis?

It lowers the rate of photosynthesis. Signup and view all the answers

What percentage of total water loss in plants is attributed to lenticular transpiration?

1 – 5% Signup and view all the answers

What role do guard cells play in stomatal transpiration?

They regulate the opening and closing of stomata. Signup and view all the answers

Which of the following correctly describes the effect of stomatal transpiration on plant cooling?

It provides a significant cooling effect. Signup and view all the answers

What is the primary process discussed that converts biochemical energy from nutrients into ATP?

Aerobic cellular respiration Signup and view all the answers

In what way does transpiration impact mineral transport in plants?

It facilitates the movement of minerals absorbed by the roots. Signup and view all the answers

Where does glycolysis occur within the cell?

Cytoplasm Signup and view all the answers

What is the overall chemical reaction that summarizes cellular respiration?

C6H12O6 + 6O2 → 6CO2 + 6H2O Signup and view all the answers

What are lenticels and where are they found?

Small openings in the woody stem and fruits. Signup and view all the answers

Which statement about turgidity and guard cells is correct?

Increased turgidity in guard cells causes the stomatal opening to widen. Signup and view all the answers

Which phase of glycolysis involves splitting glucose using ATP?

1st phase Signup and view all the answers

What occurs during the second phase of glycolysis?

Creation of ATP and NADH Signup and view all the answers

Lenticular transpiration and stomatal transpiration are similar in that they both involve:

The loss of water vapor. Signup and view all the answers

What structural change occurs in plants that becomes more robust against pests and disease?

Thickening of cell walls. Signup and view all the answers

Which form of respiration occurs in the presence of oxygen?

Aerobic respiration Signup and view all the answers

What challenge does O2 present during the process of carbon fixation?

O2 and CO2 compete for the active site of enzymes Signup and view all the answers

What condition leads to a yellowing of leaves, known as chlorosis?

Infection or lack of minerals Signup and view all the answers

What is produced during the Krebs Cycle in aerobic respiration?

NADH and FADH2 Signup and view all the answers

Which statement is true regarding anaerobic respiration?

End products include ethanol and CO2. Signup and view all the answers

Where does the electron transport chain occur in eukaryotic cells?

Mitochondrial membranes Signup and view all the answers

Which of the following is a byproduct of alcoholic fermentation?

Ethanol Signup and view all the answers

What is the main difference between lactic acid and alcoholic fermentation?

Alcoholic fermentation regenerates NAD+ through acetaldehyde. Signup and view all the answers

What is the overall equation for anaerobic fermentation?

Glucose → 2 Ethanol + 2 CO2 + 2 ATP Signup and view all the answers

Which process occurs during aerobic respiration but not during anaerobic respiration?

Krebs Cycle Signup and view all the answers

What molecule is regenerated during lactic acid fermentation?

NAD+ Signup and view all the answers

What effect does a high number of leaves have on transpiration rate?

It increases the transpiration rate. Signup and view all the answers

Which internal factor would reduce the rate of transpiration?

Presence of a thick cuticle Signup and view all the answers

What happens to the concentration of sugar solutions in fruits when transpiration is rapid?

It becomes more concentrated, increasing sweetness. Signup and view all the answers

Which external factor can increase the transpiration rate?

High wind movement Signup and view all the answers

How does the size of leaves affect transpiration rate?

Bigger leaves result in a higher transpiration rate. Signup and view all the answers

What is the role of stomata in transpiration?

They increase water loss by providing pores. Signup and view all the answers

Which factor does NOT affect the rate of transpiration?

Leaf age Signup and view all the answers

What happens if there is a low concentration of CO2 around a plant?

It decreases transpiration rate. Signup and view all the answers

What is the relationship between temperature and stomata during transpiration?

Higher temperature causes stomata to open. Signup and view all the answers

Which condition is likely to lower the transpiration rate of a plant?

High relative humidity Signup and view all the answers

Study Notes

Plant Physiology

Plants have two transportation systems
Substances move via two types of transport tissues
Xylem transports water and solutes from roots to leaves via transpiration
Phloem transports food (sugars and amino acids) from leaves to other plant parts via translocation
Xylem tissues carry water and minerals; one-way flow
Phloem tissues carry food down from the leaves; two-way flow

Transportation in Plant

Xylem
- One-way flow
- No end walls between cells
- Thick walls stiffened with lignin; supports the plant tissue
Phloem
- Two-way flow
- End walls with perforations (sieve plates)
- Cells have end walls with perforations

The Vascular Bundle Structure

Stem and root structures
Vascular bundles composed of phloem, cambium and xylem
Cambium cells make new xylem and phloem
Epidermis of stem and root protects and reduces water loss
Root hairs absorb water and mineral salts

Transpiration

Transpiration is the loss of water vapor through the stomata; it results in the upward movement of water through the plant from roots to leaves
- Water evaporates from leaves
- Veins carry water into leaves
- Water is drawn up the stem to the leaves
- Roots take up water from the soil
90% of water absorbed by roots is lost through transpiration
3 types of transpiration
- Cuticular
- Lenticular
- Stomatal

Types of Transpiration

Cuticular
- Loss of water vapor through the cuticle (layer of wax)
- Minimizes water loss from leaf surface
- Thicker cuticle, the lesser transpiration rate
Lenticular
- Loss of water vapor through lenticels (small openings) in woody stems and fruits.
- Water evaporates from cell surfaces
- Accounts for 1-5% of total water loss
Stomatal
- Loss of water vapor through stomata on leaves; the main form of transpiration.
- Stomata open when guard cells are turgid; closes when flaccid
- Regulates water loss and gas exchange
- Accounts for 85-90% of total water loss
Internal and external factors affect transpiration rate

Translocation

Translocation is the movement of materials from leaves to other plant parts
Food (sugars, amino acids) is transported from sources (leaves) to sinks (growth regions) through phloem tissues.
Phloem tissues are vascular bundles that run throughout the plant in strands, extending from roots into leaves
The mass flow hypothesis describes the movement of sugars through the phloem
Sucrose is loaded into companion cells, then into sieve-tube elements, creating a concentration gradient and thus driving water flow through the phloem
Factors influencing translocation include proximity of sources and sinks, growth hormones, and external factors (water/mineral stress, light/temperature, effects of carbon dioxide)

Photosynthesis

Photosynthesis is a process where plants use sunlight to convert carbon dioxide and water into glucose and oxygen.
Chlorophyll traps sunlight energy, driving chemical reactions
Occurs in chloroplasts, mainly in mesophyll cells of leaves.

Stages of Photosynthesis

Light-dependent reactions
- Occurs in thylakoid membranes of chloroplasts
- Uses light energy to split water, producing oxygen, ATP, and NADPH.
Light-independent reactions (Calvin cycle)
- Occurs in stroma of chloroplasts
- Uses ATP and NADPH from light-dependent reactions to convert carbon dioxide into glucose.

Factors Affecting Photosynthesis

Internal: Number of leaves, number stomata, size of leaves, leaf structure
External: Light intensity, temperature, CO2 concentration, water availability, O₂ concentration, chlorophyll concentration

Cellular Respiration

Cellular respiration is a process that converts chemical energy in food (glucose) into chemical energy in the form of ATP
ATP powers essential life processes
Overall reaction: glucose + oxygen → carbon dioxide + water + ATP

Stages of Cellular Respiration

Glycolysis
- Occurs in cytoplasm
- Glucose is broken down into pyruvate, producing a small amount of ATP and NADH.
Krebs cycle (Citric acid cycle)
- Occurs in mitochondrial matrix
- Pyruvate is further broken down, producing CO2, ATP, NADH, and FADH2.
Electron transport chain
- Occurs in inner mitochondrial membrane
- NADH and FADH2 release electrons, generating a proton gradient used to produce a large amount of ATP.

Types of Cellular Respiration

Anaerobic respiration (fermentation)
- Occurs without oxygen
- Products are lactic acid (muscle cells) or ethanol and CO2(plant, yeast).
Aerobic respiration
- Occurs with oxygen
- Produces much more ATP, essential for most organisms

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Description

This quiz explores the mechanisms of photosynthesis and the transport of sugars within plants, particularly focusing on the role of companion cells and sieve tubes. It covers key concepts including the Calvin Cycle, light-dependent reactions, and factors affecting photosynthesis. Test your understanding of these vital plant processes!