Plant Nutrition: Photosynthesis Factors

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Questions and Answers

What is the purpose of using a paperclip in the experiment?

To attach the plant to the beaker

To measure the distance from the lamp

To hold the top of the plant down (correct)

To mark the water level in the beaker

How should the lamp be positioned during the experiment?

At a distance that varies randomly

Closer after every bubble count

As close as possible to the beaker (correct)

At a fixed distance from the plant

What measurement is recorded alongside bubble counts?

The temperature of the water

The type of plant used

The size of the beaker

The distance from the lamp (correct)

Why is it necessary to repeat the bubble count multiple times?

To obtain an average for accuracy Signup and view all the answers

What should be done after recording bubble counts at different distances?

Create a line graph with distance and mean bubbles Signup and view all the answers

What does the number of bubbles released indicate in this experiment?

The rate of photosynthesis Signup and view all the answers

What factor is being varied during the experiment?

Distance from the lamp to the plant Signup and view all the answers

What is the expected outcome as the distance from the lamp increases?

Decreased number of bubbles released Signup and view all the answers

What should be plotted on the x-axis of a line graph in this experiment?

Mass of sodium hydrogencarbonate added Signup and view all the answers

Which of the following is a key requirement when plotting points on a line graph?

Points must be plotted as neat crosses and lines should be drawn with a pencil Signup and view all the answers

What is the function of the hydrogencarbonate indicator in the investigation?

To indicate changes in carbon dioxide concentration Signup and view all the answers

Which action should be carried out first in the method provided?

Pour hydrogencarbonate indicator into the test tubes Signup and view all the answers

What is a potential difficulty one might encounter during the experiment?

Difficulty in observing color changes Signup and view all the answers

What is suggested for improving the experiment if more time were available?

Increasing the number of aquatic plants used Signup and view all the answers

Which of these factors is considered the dependent variable in this experiment?

Number of bubbles per minute Signup and view all the answers

What happens to the rate of photosynthesis when light intensity increases beyond point B?

The rate of photosynthesis stays the same. Signup and view all the answers

What are the expected color changes of the hydrogencarbonate indicator indicative of?

Increasing acidity level in the water Signup and view all the answers

Which factor becomes a limiting factor when carbon dioxide concentration is low?

Light intensity. Signup and view all the answers

How does temperature affect the rate of photosynthesis?

Higher temperatures generally increase the rate of photosynthesis. Signup and view all the answers

What role do stomata play in photosynthesis?

They allow carbon dioxide to enter the leaf. Signup and view all the answers

What occurs when the stomata are closed on a hot day?

Photosynthesis cannot take place. Signup and view all the answers

What is the purpose of destarching a plant in an experiment?

To ensures that any starch found is produced during the experiment Signup and view all the answers

At what point does carbon dioxide no longer increase the rate of photosynthesis?

When carbon dioxide concentration is at its maximum level. Signup and view all the answers

Which of these statements accurately describes the effect of light intensity on photosynthesis?

There is a maximum light intensity beyond which photosynthesis rate does not change. Signup and view all the answers

Why is it important for the leaf to remain attached to the plant for a day after applying black paper?

To give the plant time to photosynthesize and produce starch Signup and view all the answers

In an experiment investigating if light is necessary for photosynthesis, what serves as the control?

The part of the leaf that is exposed to light Signup and view all the answers

Which condition can slow down photosynthesis despite high light intensity and carbon dioxide levels?

Closed stomata. Signup and view all the answers

Which part of the leaf was compared in the experiment to test for chlorophyll's necessity for photosynthesis?

The white (non-chlorophyll) parts and the green parts Signup and view all the answers

What would happen if the entire leaf was covered in an experiment testing light's effect on photosynthesis?

It would not provide conclusive evidence whether the plant can photosynthesize Signup and view all the answers

What is a crucial step to ensure safe handling of alcohol in the experiment?

Turn off the burner before collecting the alcohol Signup and view all the answers

In an investigation about the necessity for carbon dioxide in photosynthesis, what is the primary method of comparison?

Comparing two leaves on the same plant, one with carbon dioxide and one without Signup and view all the answers

What must be ensured about the plant before starting any experiments related to starch production?

It should be destarched before the experiment begins Signup and view all the answers

What color indicates a high concentration of carbon dioxide in a tube with a plant in the dark?

yellow Signup and view all the answers

Which tube shows a low concentration of carbon dioxide when a plant is present and exposed to light?

Tube with a plant in light Signup and view all the answers

What is the primary reason a plant in bright light produces more oxygen than it uses?

Photosynthesis occurs at a higher rate than respiration. Signup and view all the answers

Which condition would lead to the color orange-red in a tube with no plant?

Tube without a plant in the light Signup and view all the answers

What effect does wrapping a tube in black paper have on the gas exchange of the aquatic plant?

It blocks light, preventing photosynthesis. Signup and view all the answers

Which of the following statements is true regarding the gas exchange in the experiment?

Respiration occurs all the time in plants. Signup and view all the answers

What color does the indicator change to in a tube with a plant both in light and without carbon dioxide?

purple Signup and view all the answers

What should be done with the tubes after observing the color change of the indicator?

Remove the black paper from both covered tubes. Signup and view all the answers

What is indicated by curve B in the graph regarding carbon dioxide concentration during photosynthesis?

It demonstrates a faster rate of photosynthesis. Signup and view all the answers

What is NOT a benefit of using a glasshouse for plant growth?

Winter crops can be cultivated during summer. Signup and view all the answers

How can growers increase carbon dioxide concentration in a glasshouse?

By burning butane or natural gas. Signup and view all the answers

What does insufficient light intensity in a glasshouse require?

Adding artificial light with reflectors. Signup and view all the answers

Which of the following statements about light intensity and photosynthesis is true?

Carbon dioxide concentration can become a limiting factor at high light intensity. Signup and view all the answers

What characterizes a glasshouse?

It is designed to allow plant growth year-round. Signup and view all the answers

Which factor can specifically be adjusted in a glasshouse to optimize photosynthesis?

Light intensity and carbon dioxide levels. Signup and view all the answers

Which of the following scenarios can occur in a glasshouse?

Crops from warm climates can be grown in cooler locations. Signup and view all the answers

Study Notes

Plant Nutrition: Factors Affecting Photosynthesis

Controls & Experimental Groups:
- Control groups receive all necessary substances, the substance being tested is NOT included.
- Experimental groups receive everything except the substance being tested
- Experimental control is designed to test a certain variable.

Plant Nutrition: Testing Leaves for Starch

Destarching Plants: Plants are left in a dark cupboard for 24 hours. This causes them to use up their stored starch reserves as they cannot photosynthesize in the absence of light.
Importance of Destarching: Ensures any starch detected is generated during the experiment, not stored before.

Experimental Skills 6.1: Testing a Leaf for Starch

Purpose: To identify if a leaf has been photosynthesizing
Materials: 250 cm³ beaker, burner, tripod and gauze, boiling tube, some iodine solution, forceps, alcohol (methylated spirits), fresh green leaf, white tile.
Safety Precautions: Alcohol is flammable, do not collect the alcohol until you have turned out the burner, put a damp cloth over the alcohol if it burns.
Method:
1. Boil water in a beaker.
2. Place a leaf in boiling water to break down cell membranes and denature enzymes.
3. Turn out the flame.
4. Place leaf in alcohol to dissolve the chlorophyll.
5. Remove leaf from alcohol and place in hot water.
6. Place leaf on white tile and add iodine solution
7. Blue-black color indicates presence of starch.

Experimental skills 6.1/Questions and Answers

Chlorophyll Dissolving: Alcohol dissolves chlorophyll, a green pigment in leaves
Boiling Water: Boiling water breaks down cell membranes, allowing chlorophyll to leave.
Observation/Conclusion: Blue-black color indicates starch. This suggests photosynthesis occurred.

Experimental Skills 6.2: Investigating the Necessity for Chlorophyll for Photosynthesis

Variegated Leaves: Leaves with both green and white patches, green parts contain chlorophyll, while white parts do not.
Method:
1. Draw the variegated leaf, label green and white parts.
2. Test the leaf for starch, following the procedure described earlier.
3. Record observations by drawing and labeling the leaf after adding iodine solution.

Experimental Skills 6.2/Questions and answers

Starch Location: Green parts of the leaf contained starch, indicating chlorophyll presence.
Conclusion: Chlorophyll is essential for photosynthesis, as starch is only present in the parts of the leaf where chlorophyll was present.

Experimental Skills 6.3: Investigating the Necessity for Light for Photosynthesis

Method: Cover part of a leaf with black paper to block light.
Method: 1. Create a shape or initials in black paper to attach to leaf on plant. 2. Attach to leaf on plant. 3. Place plant in a sunny area for 24 hours. 4. Remove leaf and paper. 5. Test leaf for starch following the procedure. 6. Record results by drawing and labeling the leaf after adding iodine solution

Experimental skills 6.3/Questions and answers

Importance of Destarching: Destarching ensures that any observed starch is a product of the experiment's new light exposure and not from previous, non-experimental, photosynthesis.
Duration of Experiment: The leaf must remain attached for at least 24 hours

Experimental Skills 6.4: Investigating the Necessity for Carbon Dioxide for Photosynthesis

Materials: Healthy potted plant, 2 transparent containers (e.g., conical flasks), 2 rubber stoppers with slits to fit, potassium hydroxide solution, distilled water, petroleum jelly,
Method: Design and set up apparatus, place plant in either one of two containers labeled one carbon dioxide and the other without.
1. Set up the apparatus as in Figure 6.20, taking note of precautions to prevent air entering.
2. Fill one flask with potassium hydroxide (to remove carbon dioxide) and other flask with distilled water.
3. Place the leaf stalk in one rubber bung carefully positioning into one of the flasks and securing with the bung.
4. Repeat the process with another leaf.
5. Place setup in a light place for 1 day.
6. Remove the apparatus from the light.
7. Test leaves for starch.

Experimental Skills 6.4/Questions and answers

Control: A leaf in distilled water serves as a control, allowing the researcher to observe any discrepancies due to carbon dioxide’s presence.
Purpose of Potassium Hydroxide: The potassium hydroxide absorbs carbon dioxide, creating a comparative testing space for the effect of carbon dioxide absorption.

Experimental Skills 6.5: Investigating the Effect of Varying Light Intensity on the Rate of Photosynthesis

Materials: Healthy aquatic plant (with stems), Beaker, Water, Lamp, Ruler, and timer
Method: Measure the distance between the lamp and the plant.
1. Collect a piece of aquatic plant. Cut off a piece about 7 to 9 cm long to be able to use in the experiment.
2. Set up the apparatus and attach the paper clip to the top of the plant. Ensure the end of the cut stem floats upwards.
3. Place lamp as close to beaker as possible and measure distance.
4. Record the number of bubbles produced by the cut stem of the aquatic plant for 1 minute of light intensity using a timer for time measurement.
5. Repeat steps 2-3 five different times (increasing the light intensity/ distance from the plant from the lamp) to get reliable data sets.
6. Create a line graph with distance on the x-axis and mean number of bubbles (over 3 trials) produced in 1 minute on the y-axis.

Plant Nutrition: Limiting Factors in Photosynthesis

Limiting Factors: These are factors that reduce the rate of photosynthesis. These include Light intensity, Carbon dioxide concentration, and Temperature.
Light Intensity: Photosynthesis increases with light intensity, until the maximum rate is reached and another limiting factor takes over.
Carbon Dioxide Concentration: Photosynthesis increases as carbon dioxide concentration increases, only up to a certain point where a different limiting factor takes over.
Temperature: Enzymtic reactions limit the rate of photosynthesis at lower temperatures. As the temperature increases, the reactions also increase until an optimal temperature is reached.

Two Limiting Factors at Once

When there is more than one limiting factors in an experiment, it is necessary to create different values/ conditions for the chosen limiting factor to observe the rate of photosynthesis and how different levels of the selected variable affect the rate.

Stomata

Stomata are openings in plant leaves; carbon dioxide enters through stomata, allowing for photosynthesis.
Stomata may close in hot or bright conditions, due tothe loss of water, reducing photosynthetic rates.

Glasshouses: Optimizing Conditions

Temperature: Glasshouses can regulate temperature, either heating or allowing for ventilation to maintain optimal conditions. This is essential for some plant types.
Water: Automatic watering systems are often used in glasshouses to ensure optimal water availability. Water needs can be altered according to plant type.
Light Intensity: For insufficient light, artificial light or reflectors help to increase the available light. If the light intensity is too high, blinds/shade can be used to reduce the intensity.
Carbon dioxide: Carbon dioxide can be increased via addition of carbon dioxide gas, which can increase photosynthesis rates .

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Description

Explore the essential factors impacting photosynthesis in plants through this quiz. Understand the roles of control and experimental groups, the process of destarching, and how to test leaves for starch presence. Test your knowledge and deepen your understanding of plant nutrition.