Water Absorption in Plants
Plants absorb nutrients (in the form of salts or ions) and water from the soil with the help of roots.
- The procedure by which plants take up compounds from the soil is known as absorption.
- The root is an underground cylindrical part of a plant that grows vertically down in the soil and help in absorption.
- Active absorption describes the absorption of water by roots with the help of adenosine triphosphate, generated by root respiration: as the root cells actively participate in the procedure, it is called active absorption.
- Root pressure, guttation, and bleeding are the manifestations of active water absorption.
- The evidence suggests that passive absorption represents the majority of the water taken in by plants.
- Active absorption is very important only in gradually taking place plants growing in the soil near field capacity.
Factors affect the absorption of water by root
1. Availability of Soil Water
- (a) Plant takes in capillary water, which exists in the soil. Absorption of water depends upon the quantity of capillary water present in the soil. Absorption is boosted by the increasing amount of capillary water.
- (b) If water exists in a greater amount in the soil then such kind of soil is called “Water logged soil”. This soil is Physiologically dry and lacks oxygen. Because of this anaerobic respiration happens in roots, and alcohol is formed. Roots can degenerate due to the form action of alcohol.
2. Soil temperature
An increase in soil temperature level up to about 30 ° C favors water absorption. At greater temperature water absorption is decreased. At low-temperature levels likewise, water absorption is reduced so much so that at about 0 ° C, it is practically reduced. This is probably because at low-temperature levels:
- The viscosity of water and protoplasm is increased
- The permeability of cell membrane is decreased
- The metabolic activity of root cells is reduced
- Root development and elongation of roots are examined.
3. Soil air
Water absorption likewise requires energy. This energy is released in the process of respiration. Oxygen is needed for respiration. This oxygen is provided by soil air. Absorption of water is slowed down in badly aerated soils because in such soils shortage of O2 and as a result the build-up of CO2 will retard the metabolic activities of roots like respiration.
This also inhibits the fast development and elongation of the roots so that they are deprived of a fresh supply of water in the soil. Waterlogged soils are poorly aerated and for this reason, are physiologically dry. They are bad for the absorption of water.
4. Soil Concentration
(a) The rate of absorption is inversely proportional to the concentration of minerals present in the soil.
Water Absorption x 1/Concentration of soil minerals
(b) Water absorption only occurs in proper soil solution. The soil ought to be hypotonic and the plant needs to be hypertonic to perform the procedure of endosmosis. If the concentration of soil minerals is high, it decreases the rate of absorption, and plasmolysis and wilting occur.
5. Association of Mycorrhizae
Mycorrhizae is an association of fungi and roots of higher plants. Fungi increase the ability to absorb water through roots.
6. Transpiration
According to Kramer, the rate of water absorption is directly proportional to the rate of transpiration. The rate of transpiration increases the rate of absorption of water by the root. Transpiration produces transpiration pull in the xylem vessels. It pulls water up. Thus, negative pressure is produced in the xylem of the root. It absorbs water from the soil.
MCQs
- What is the primary function of roots in water absorption?
- A) Synthesizing nutrients
- B) Anchoring the plant
- C) Absorbing water and nutrients
- D) Providing support to stems
- Answer: C) Absorbing water and nutrients
- Which type of absorption involves the active participation of root cells and requires adenosine triphosphate (ATP)?
- A) Passive absorption
- B) Capillary absorption
- C) Active absorption
- D) Endosmotic absorption
- Answer: C) Active absorption
- What are manifestations of active water absorption?
- A) Capillary action and guttation
- B) Root pressure, guttation, and bleeding
- C) Endosmosis and exosmosis
- D) Osmosis and transpiration
- Answer: B) Root pressure, guttation, and bleeding
- In which type of soil does water absorption get hampered due to anaerobic respiration and alcohol formation?
- A) Sandy soil
- B) Loamy soil
- C) Waterlogged soil
- D) Clayey soil
- Answer: C) Waterlogged soil
- What effect does an increase in soil temperature up to about 30 °C have on water absorption?
- A) Increases water absorption
- B) Decreases water absorption
- C) No effect on water absorption
- D) Promotes endosmotic absorption
- Answer: A) Increases water absorption
- What factor is responsible for providing oxygen needed for root respiration during water absorption?
- A) Soil minerals
- B) Soil air
- C) Soil temperature
- D) Soil concentration
- Answer: B) Soil air
- Why is water absorption slowed down in poorly aerated soils?
- A) Excessive oxygen availability
- B) Rapid root metabolism
- C) Accumulation of CO2 and O2 deficiency
- D) Increased water viscosity
- Answer: C) Accumulation of CO2 and O2 deficiency
- What does the rate of absorption depend on, according to the concentration of minerals in the soil?
- A) It is directly proportional
- B) It is inversely proportional
- C) It is not affected by soil concentration
- D) It follows endosmotic absorption
- Answer: B) It is inversely proportional
- What type of soil solution is necessary for water absorption through endosmosis?
- A) Hypertonic soil with hypertonic plant
- B) Hypotonic soil with hypotonic plant
- C) Hypertonic soil with hypotonic plant
- D) Hypotonic soil with hypertonic plant
- Answer: B) Hypotonic soil with hypotonic plant
- How does the association of mycorrhizae contribute to water absorption by roots?
- A) It inhibits water absorption
- B) It decreases root development
- C) It reduces root metabolism
- D) It increases the ability of water absorption
- Answer: D) It increases the ability of water absorption
- According to Kramer, what is the relationship between the rate of water absorption and transpiration?
- A) Inversely proportional
- B) Directly proportional
- C) No correlation
- D) Transpiration inhibits water absorption
- Answer: B) Directly proportional
- What is the primary function of roots in water absorption?
- A) Synthesizing nutrients
- B) Anchoring the plant
- C) Absorbing water and nutrients
- D) Providing support to stems
- Answer: C) Absorbing water and nutrients
- Which type of absorption involves the active participation of root cells and requires adenosine triphosphate (ATP)?
- A) Passive absorption
- B) Capillary absorption
- C) Active absorption
- D) Endosmotic absorption
- Answer: C) Active absorption
- What are manifestations of active water absorption?
- A) Capillary action and guttation
- B) Root pressure, guttation, and bleeding
- C) Endosmosis and exosmosis
- D) Osmosis and transpiration
- Answer: B) Root pressure, guttation, and bleeding
- In which type of soil does water absorption get hampered due to anaerobic respiration and alcohol formation?
- A) Sandy soil
- B) Loamy soil
- C) Waterlogged soil
- D) Clayey soil
- Answer: C) Waterlogged soil
- What effect does an increase in soil temperature up to about 30 °C have on water absorption?
- A) Increases water absorption
- B) Decreases water absorption
- C) No effect on water absorption
- D) Promotes endosmotic absorption
- Answer: A) Increases water absorption
- What factor is responsible for providing oxygen needed for root respiration during water absorption?
- A) Soil minerals
- B) Soil air
- C) Soil temperature
- D) Soil concentration
- Answer: B) Soil air
- Why is water absorption slowed down in poorly aerated soils?
- A) Excessive oxygen availability
- B) Rapid root metabolism
- C) Accumulation of CO2 and O2 deficiency
- D) Increased water viscosity
- Answer: C) Accumulation of CO2 and O2 deficiency
- What does the rate of absorption depend on, according to the concentration of minerals in the soil?
- A) It is directly proportional
- B) It is inversely proportional
- C) It is not affected by soil concentration
- D) It follows endosmotic absorption
- Answer: B) It is inversely proportional
- What type of soil solution is necessary for water absorption through endosmosis?
- A) Hypertonic soil with hypertonic plant
- B) Hypotonic soil with hypotonic plant
- C) Hypertonic soil with hypotonic plant
- D) Hypotonic soil with hypertonic plant
- Answer: B) Hypotonic soil with hypotonic plant
- How does the association of mycorrhizae contribute to water absorption by roots?
- A) It inhibits water absorption
- B) It decreases root development
- C) It reduces root metabolism
- D) It increases the ability of water absorption
- Answer: D) It increases the ability of water absorption
- According to Kramer, what is the relationship between the rate of water absorption and transpiration?
- A) Inversely proportional
- B) Directly proportional
- C) No correlation
- D) Transpiration inhibits water absorption
- Answer: B) Directly proportional
- What physiological process is associated with the term “guttation”?
- A) Active absorption
- B) Root pressure
- C) Transpiration
- D) Endosmosis
- Answer: B) Root pressure
- What is the term for the process of water absorption occurring against the concentration gradient, requiring energy?
- A) Passive absorption
- B) Capillary absorption
- C) Active absorption
- D) Osmotic absorption
- Answer: C) Active absorption
- How does low soil temperature affect water absorption by roots?
- A) Increases water absorption
- B) Decreases water absorption
- C) No effect on water absorption
- D) Promotes endosmotic absorption
- Answer: B) Decreases water absorption
- What is the role of soil air in the absorption of water by roots?
- A) Provides nutrients
- B) Releases energy
- C) Supplies oxygen for respiration
- D) Enhances root metabolism
- Answer: C) Supplies oxygen for respiration
- What does the term “endosmosis” refer to in the context of water absorption by roots?
- A) Movement of water out of the root
- B) Movement of water into the root
- C) Movement of water along the root surface
- D) Movement of water towards the soil
- Answer: B) Movement of water into the root
- What happens in waterlogged soils that makes them unfavorable for water absorption?
- A) Excessive root elongation
- B) High oxygen availability
- C) Poor aeration and anaerobic respiration
- D) Increased metabolic activity
- Answer: C) Poor aeration and anaerobic respiration
- How does the association of mycorrhizae contribute to water absorption?
- A) Inhibits water absorption
- B) Reduces root metabolism
- C) Increases root development
- D) Increases the ability of water absorption
- Answer: D) Increases the ability of water absorption
- What is the relationship between the rate of water absorption and the concentration of minerals in the soil?
- A) Directly proportional
- B) Inversely proportional
- C) No correlation
- D) Promotes endosmotic absorption
- Answer: B) Inversely proportional
FAQs – Factors Affecting Water Absorption in Plants
1. What is the primary role of roots in water absorption in plants?
- Roots play a crucial role in absorbing water and nutrients from the soil.
2. What is active absorption, and how is it related to root respiration?
- Active absorption is the process of water absorption by roots with the help of adenosine triphosphate (ATP) generated through root respiration. Root pressure, guttation, and bleeding are manifestations of active water absorption.
3. Which type of water absorption predominates in plants, and in what conditions is active absorption significant?
- Passive absorption is the predominant mode of water absorption. Active absorption is significant in slowly occurring plants growing in soil near field capacity.
4. How does the availability of soil water impact water absorption?
- Water absorption depends on the quantity of capillary water present in the soil. An increase in capillary water enhances absorption.
5. What are the consequences of excessive water in soil, leading to waterlogged conditions?
- Waterlogged soil, with an abundance of water, results in physiologically dry conditions, leading to anaerobic respiration in roots and alcohol formation, potentially causing root degeneration.
6. How does soil temperature influence water absorption in plants?
- An increase in soil temperature up to about 30 °C favors water absorption. Higher or lower temperatures can decrease water absorption due to changes in viscosity, permeability, and metabolic activity.
7. What role does soil air play in the absorption of water by roots?
- Soil air supplies oxygen for respiration, a process essential for water absorption. Poorly aerated soils slow down absorption due to oxygen deficiency and the accumulation of CO2, impacting root metabolism.
8. How does soil concentration affect the rate of water absorption?
- The rate of water absorption is inversely proportional to the concentration of minerals in the soil. Higher soil mineral concentration reduces the absorption rate, leading to plasmolysis and wilting.
9. What is the significance of the association of mycorrhizae in water absorption?
- Mycorrhizae, an association of fungi and plant roots, enhance the ability of roots to absorb water.
10. What is the relationship between the rate of water absorption and transpiration, according to Kramer?
- Kramer suggests that the rate of water absorption is directly proportional to the rate of transpiration. Transpiration creates a pull in the xylem vessels, facilitating water absorption by the roots.
Summary – Factors Affecting Water Absorption in Plants
In this tutorial on factors influencing water absorption in plants, we explored the intricate process by which plants absorb nutrients and water through their roots from the soil. The absorption, a crucial function performed by roots, involves active absorption, relying on adenosine triphosphate (ATP) generated through root respiration, as well as passive absorption, which is predominant in most plants.
The tutorial highlighted key factors affecting water absorption:
- Availability of Soil Water:
- The amount of capillary water in the soil significantly influences water absorption. Excessive water, as seen in waterlogged soils, can lead to physiologically dry conditions due to anaerobic respiration.
- Soil Temperature:
- Optimal soil temperature around 30°C enhances water absorption, while extremes (high or low) can reduce absorption. Factors such as increased viscosity, decreased permeability, and reduced metabolic activity in roots contribute to temperature-related variations.
- Soil Air:
- Energy for water absorption is derived from respiration, requiring oxygen supplied by soil air. Poorly aerated soils limit oxygen availability, slowing down water absorption and hindering root development.
- Soil Concentration:
- The rate of water absorption is inversely proportional to the concentration of minerals in the soil. Higher mineral concentration hampers absorption, leading to plasmolysis and wilting.
- Association of Mycorrhizae:
- Mycorrhizae, a symbiotic association of fungi and plant roots, plays a vital role in enhancing the water absorption capability of roots.
- Transpiration:
- Kramer’s theory suggests a direct proportionality between the rate of water absorption and transpiration. Transpiration pull in xylem vessels, driven by negative pressure, facilitates the uptake of water from the soil.
Throughout the tutorial, we delved into the intricate processes and interactions that influence the plant’s ability to absorb water, providing valuable insights into the dynamic relationship between plants and their environment.