Transport In Plants

边玩边学

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课程笔记

Xylem & Phloem

Xylem vessels transport water and minerals from roots to stem and leaves, and provide support.
Phloem vessels transport food (mainly sucrose and amino acids) from leaves to other parts.
Xylem and phloem are arranged in vascular bundles throughout root, stem and leaves.
In cross-section, xylem is always on the inside and phloem on the outside.

Vascular tissues in a dicotyledonous plant

Root Hair Cells

Root hair cells are found in the epidermis of plant roots.
They have root hairs that grow between soil particles, increasing surface area.
This adaptation aids absorption of water and mineral ions from the soil.

Root hair cells: structure and location

Pathway Taken by Water

Water enters root hair cells by osmosis.
It then moves through root cortex cells into xylem vessels.
Water is carried up the xylem to leaf mesophyll cells.
Pathway: root hair cell → root cortex cells → xylem → leaf mesophyll cells.

Water pathway from soil to xylem

Transpiration

Transpiration is the loss of water vapour from leaves.
Water evaporates from spongy mesophyll cells into air spaces.
Water vapour then diffuses out through stomata.

Transpiration through a leaf

Investigating Temperature & Wind Speed

Use a potometer to measure transpiration rate.
Cut shoot underwater to prevent air entering xylem.
Seal apparatus with Vaseline to make it airtight.
Introduce a single air bubble in the capillary tube.
Measure distance bubble moves in a set time (e.g. 20 min).
Higher temperature or higher wind speed increases transpiration rate.
Keep all other factors constant for a fair test.

Using a bubble potometer

Explaining Effects of Temperature, Wind Speed & Humidity

High temperature increases evaporation and diffusion rate, so transpiration increases.
High wind speed removes water vapour near leaf, maintaining concentration gradient, so transpiration increases.
High humidity reduces concentration gradient, so transpiration decreases.
If water loss exceeds uptake, wilting occurs – cells lose turgor and plant collapses.

Wilting compared with a well-watered plant

Translocation

Translocation is the transport of sucrose and amino acids in phloem.
Glucose is converted to sucrose for transport.
Phloem cells are joined end-to-end with holes in end walls for easy flow.
Movement is from source (where produced) to sink (where used/stored).
Direction can change: e.g. in spring, storage organs are source; in summer, leaves are source.

Translocation in the phloem

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练习题

免费预览——53 题中的 8 题。注册即可查看全部。

1.Name the two types of transport vessels in plants.
Easy
2.Transpiration is the loss of water vapour from the leaves of plants.
Easy
True or false?
3.Complete the sentence about the pathway of water:
Easy
Water enters the root hair cells, passes through the root cortex, then enters the ____ vessels, and finally reaches the leaf mesophyll cells.
4.Match each plant structure with its correct function.
Medium
- Xylem
- Phloem
- Root hair cell
- Absorbs water and minerals
- Transports water and minerals
- Transports sucrose and amino acids
5.Which factor increases the rate of transpiration?
Easy
- ALow temperature
- BHigh humidity
- CHigh wind speed
- DLow light intensity
6.State two environmental factors that affect the rate of transpiration.
Easy
7.Translocation is the transport of sucrose and amino acids in the phloem from sources to sinks.
Easy
True or false?
8.In a potometer experiment, the air bubble moves 8 mm in 20 minutes at 20°C. What is the rate of transpiration in mm per minute?
Medium
- A1.4
- B-0.6
- C0.4
- D2.4

更多题目

9.Complete the sentence:
Medium
During winter, when many plants have no leaves, the phloem may transport sucrose from storage organs (the ____) to other parts of the plant (the ____).
10.Which of the following is the function of xylem vessels?
Easy
- ATransport of water and minerals from roots to leaves
- BTransport of sucrose and amino acids from leaves to roots
- CTransport of carbon dioxide from leaves to roots
- DTransport of oxygen from roots to leaves
11.What is the primary function of root hair cells?
Easy
- ATo absorb water and mineral ions from the soil
- BTo transport sugars to the leaves
- CTo provide structural support to the root
- DTo carry out photosynthesis
12.Which of the following correctly describes the pathway of water from the soil into the xylem?
Medium
- ARoot hair cell → root cortex cells → xylem vessels
- BRoot cortex cells → root hair cell → xylem vessels
- CXylem vessels → root cortex cells → root hair cell
- DRoot hair cell → xylem vessels → root cortex cells
13.A student uses a potometer to investigate the effect of wind speed on transpiration rate. Which of the following should be kept constant during the investigation?
Medium
- ATemperature and humidity
- BWind speed only
- CLeaf surface area and humidity
- DWind speed and temperature
14.Which of the following environmental factors would increase the rate of transpiration?
Easy
- AHigh humidity
- BLow wind speed
- CHigh temperature
- DLow light intensity
15.Phloem vessels transport water and minerals from the roots to the leaves.
Easy
True or false?
16.Which of the following are transported in the phloem? (Select all that apply)
Medium
- ASucrose
- BWater
- CAmino acids
- DMineral ions
17.Match each plant transport vessel with its correct function.
Easy
- Xylem
- Phloem
- Transports water and minerals
- Transports sucrose and amino acids
18.Arrange the following structures in the correct order for the pathway of water from the soil (1) to the air (4).
Medium
- root cortex cells
- root hair cell
- xylem vessel
- leaf mesophyll cell
19.Which of the following environmental factors would decrease the rate of transpiration?
Easy
- AHigh humidity
- BHigh temperature
- CHigh wind speed
- DLow humidity
20.In a potometer experiment investigating the effect of wind speed, which variable should be kept constant?
Medium
- ATemperature
- BWind speed
- CDistance moved by bubble
- DTime taken
21.In a dicotyledonous stem, where is the xylem located relative to the phloem in a vascular bundle?
Medium
- AOn the inside (closer to centre)
- BOn the outside (closer to epidermis)
- CMixed randomly
- DXylem is absent in stems
22.Arrange the following steps in the correct order for using a potometer to investigate transpiration rate.
Medium
- Cut shoot underwater
- Dry the leaves
- Allow air bubble to form
- Record bubble movement over time
23.A student uses a potometer to investigate the effect of wind speed on transpiration rate. The student places a fan at different speeds and records the distance the air bubble moves in 20 minutes. Which of the following should be kept constant during this investigation?
Medium
- ATemperature of the room
- BSpeed of the fan
- CDistance the air bubble moves
- DTime of day
24.A plant is placed in a sealed transparent bag and left in bright sunlight. After a few hours, water droplets appear on the inside of the bag. Which process is primarily responsible for the appearance of these droplets?
Easy
- ATranspiration
- BCondensation
- CEvaporation
- DTranslocation
25.Which of the following environmental factors increase the rate of transpiration? (Select all that apply)
Medium
- AHigh temperature
- BLow humidity
- CHigh humidity
- DLow wind speed
- EHigh wind speed
26.Xylem vessels transport water and minerals from the roots to the leaves.
Easy
True or false?
27.In a potometer experiment, a student investigates the effect of temperature on transpiration rate. The results are shown in the table. | Temperature (°C) | Distance moved by air bubble in 20 min (mm) | |---|---| | 10 | 12 | | 20 | 24 | | 30 | 48 | What conclusion can be drawn from these results?
Medium
- ATranspiration rate doubles for every 10°C rise in temperature
- BTranspiration rate increases linearly with temperature
- CTranspiration rate is independent of temperature
- DTranspiration rate decreases as temperature increases
28.In a potometer experiment, a student investigates the effect of wind speed on transpiration rate. Which of the following should be kept constant?
Medium
- ATemperature and light intensity
- BWind speed and temperature
- CLeaf area and light intensity
- DWind speed and leaf area
29.In a potometer, the distance the air bubble moves is directly proportional to the rate of transpiration.
Easy
True or false?
30.Arrange the following steps in the correct order for using a potometer to measure transpiration rate.
Medium
- Dry the leaves of the shoot
- Cut the shoot underwater
- Allow a single air bubble to form in the capillary tube
- Record the starting position of the air bubble
- Place the shoot in the potometer and seal with Vaseline
31.Which of the following are correct procedures when using a potometer? (Select all that apply)
Medium
- ACut the shoot underwater
- BDry the leaves before starting
- CUse Vaseline to seal any gaps
- DPlace the potometer in direct sunlight to speed up the experiment
- EAllow the plant to adapt for 5 minutes before recording
32.A student investigates the effect of temperature on transpiration rate using a potometer. They place the potometer in a cold room (5°C) and measure the bubble movement. They then place it in a warm room (25°C) and measure again. Which variable is the dependent variable?
Medium
- ATemperature
- BDistance moved by the air bubble
- CTime
- DWind speed
33.Match each environmental factor to its effect on transpiration rate when the factor is high.
Medium
- Temperature
- Wind speed
- Humidity
- Increases transpiration rate
- Increases transpiration rate
- Decreases transpiration rate
34.In a potometer experiment, a student uses a fan to increase wind speed. The air bubble moves 15 mm in 10 minutes with the fan off, and 30 mm in 10 minutes with the fan on. What is the percentage increase in transpiration rate?
Medium
- A50%
- B100%
- C200%
- D15%
35.What is the definition of transpiration?
Easy
- AThe uptake of water by roots
- BThe loss of water vapour from the leaves of plants
- CThe transport of water in the xylem
- DThe movement of sucrose in the phloem
36.Root hair cells are found in the epidermis of plant roots.
Easy
True or false?
37.A potometer is set up with a leafy shoot. The air bubble moves 25 mm in 10 minutes at 25°C. The experiment is repeated at 15°C with all other conditions the same. Which of the following is the most likely distance moved by the air bubble in 10 minutes at 15°C?
Medium
- A12 mm
- B25 mm
- C38 mm
- D50 mm
38.Which of the following are correct procedures when using a potometer to investigate the effect of wind speed on transpiration rate? (Select all that apply)
Hard
- ACut the plant shoot underwater to prevent air from entering the xylem.
- BDry the leaves of the shoot so that water does not block the stomata.
- CUse Vaseline to seal any gaps in the apparatus to ensure it is airtight.
- DAllow the plant to adapt to the new environment for 5 minutes before recording.
- EChange both temperature and wind speed simultaneously to test multiple factors.
39.In a potometer experiment, a student dries the leaves of the shoot before starting. What is the reason for this step?
Medium
- ATo prevent the leaves from transpiring too quickly
- BTo ensure that water does not block the stomata
- CTo increase the rate of transpiration
- DTo prevent air from entering the xylem
40.In a potometer experiment, the air bubble moves 12 mm in 30 minutes at 25°C. Calculate the rate of transpiration in mm per minute.
Medium
41.Complete the sentence about root hair cell adaptation.
Medium
Root hair cells have ____ which increase the ____ for absorption of water and minerals.
42.In a potometer experiment, the air bubble moves 15 mm in 30 minutes at 25°C. Calculate the rate of transpiration in mm per hour.
Medium
43.Complete the sentence.
Easy
The transport of sucrose and amino acids in the phloem, from regions of production to regions of storage or use, is called ____.
44.State the function of root hair cells.
Easy
45.Complete the sentence about the pathway of water in a plant.
Medium
Water enters the root through r____ h____ cells, then moves through the root cortex and into the x____ vessels, and finally reaches the leaf m____ cells.
46.In a potometer experiment, the air bubble moves 18 mm in 30 minutes at 25°C. Calculate the rate of transpiration in mm per hour.
Easy
47.State one adaptation of root hair cells that helps them absorb water from the soil.
Easy
48.Explain why wilting occurs when a plant loses water faster than it can absorb it from the soil.
Medium
49.Explain how high wind speed increases the rate of transpiration.
Medium
50.Describe how you would investigate the effect of humidity on the rate of transpiration using a potometer.
Hard
51.In a potometer experiment, the air bubble moves 12 mm in 30 minutes at 25°C. Calculate the rate of transpiration in mm per minute.
Easy
- A0.4 mm/min
- B-0.6 mm/min
- C2.4 mm/min
- D1.4 mm/min
52.In a potometer experiment, the air bubble moves 15 mm in 30 minutes at 25°C. Calculate the rate of transpiration in mm per hour.
Easy
- A30 mm/h
- B33 mm/h
- C36 mm/h
- D27 mm/h
53.In a potometer experiment, the air bubble moves 18 mm in 30 minutes at 25°C. Calculate the rate of transpiration in mm per hour.
Easy
- A32 mm/h
- B40 mm/h
- C44 mm/h
- D36 mm/h

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