Plant Water Relations: Absorption, Transport and Control
Plant water relations describe how plants absorb, transport, and retain water to sustain physiological balance. Water maintains turgor pressure, photosynthesis, and nutrient transport, ensuring growth and drought tolerance. It’s a key NEET and Class 11 Biology topic under Transport in Plants.
This Story also Contains
- What are Plant Water Relations?
- Basic Concepts In Plant Water Relations
- Importance of Plant Water Relations
- Applications in Agriculture
- Plant Water Relations NEET MCQs (With Answers & Explanations)
What are Plant Water Relations?
Plant water relations entail investigating how plants regulate the intake, use, and loss of water to maintain physiological homeostasis. Water in plants is not only the medium of nutrition but also, among other things, the agent of photosynthesis and cellular turgor pressure. Plants must control their water status, from leaf hydration to root development, to be healthy and grow.
Role of Water in Plant Physiology
Understanding how plants manage water relations is very useful for optimizing agricultural practices aimed at managing and improving crop production and health. These relations are studied to practically apply this knowledge toward efficient use of water, alleviation from drought stress, and sustainable agriculture and botanical applications.
Basic Concepts In Plant Water Relations
Terms related to water relations are described below.
Water Potential
It is defined as the potential energy of water in any system. The driving energy for the movement of water is gained from the water potential. This again gets divided into three main components. They are:
Osmotic potential is the potential of water to enter a solution that arises due to the solutes dissolved in it. Sometimes it is also referred to as solute potential.
Pressure potential is the real pressure which the fluid exerts and contributes to the turgor pressure of the plant cells.
Matric potential refers to the cohesion of water molecules to surfaces present in a plant's tissues and, as such, it influences the movement of water throughout the plant and in the soil.
Osmosis
Osmosis is the passive transport of water across a semipermeable membrane from low to high solute concentrations, equalizing the concentration of solutes.
Imbibition
Imbibition is the first absorption of water either by dry seed or any plant tissues that causes them to swell and triggers off activation of physiological activity.
Plasmolysis
When a plant cell loses water to a hypertonic solution, the cell membrane pulls away from the cell wall, reducing turgor pressure and possibly causing damage to the cell.
Importance of Plant Water Relations
The importance of plant water relations include:
Maintenance of Turgor Pressure
Water helps to maintain turgor pressure which provides mechanical support. It is essential for cell growth and upright posture of plants.
Photosynthesis and Nutrient Transport
Water also ensures photosynthesis and acts as a medium for transporting minerals and nutrients from roots to leaves through the xylem.
Drought Resistance and Growth
Water relations help plants develop drought resistance by regulating stomatal closure. This ensures continued growth and survival during limited water.
Role in Transpiration and Water Balance
Water relations control transpiration, which helps in cooling the plant. By balancing water uptake and loss, plants regulate their water balance.
Applications in Agriculture
The plant water relations helps in agriculture by:
Irrigation and Water Management
Understanding plant water relations helps to design effective irrigation and maintain soil moisture. This ensures maximum crop yield and prevents waterlogging or drought stress.
Drought Mitigation Strategies
Knowledge of water relations also helps in developing drought resistant crop varieties and selecting proper irrigation methods.
Seed Germination and Growth Control
Water relations are very important for seed imbibition i.e., the first step of germination. Adequate water ensures proper growth and better productivity.
Plant Water Relations NEET MCQs (With Answers & Explanations)
The key concepts to be covered under this topic for different exams are:
Basic concepts of Plant water relations
Importance of Plant water relations
Practice Questions for NEET
Q1. Diffusion is the result of concentration gradient which refers to
Change of concentration with respect to time
Change of concentration with respect to space
Change of concentration with respect to temperature
Change of concentration with respect to gravity
Correct answer: 2) Change of concentration with respect to space
Explanation:
Movement of all substances from the area of their higher free energy to the area of their lower free energy along the concentration gradient. Neutral solutes move across the membranes by diffusion. The net direction of diffusion of particles depends on their concentration in a particular region or space.
Hence, the correct answer is option 2) Change of concentration with respect to space.
Q2. Why does an increase in temperature increase the rate of diffusion?
The increased thermal energy of the medium reduces the kinetic energy of particles
The decreased thermal energy of the medium increases the kinetic energy of particles
The increased thermal energy of the medium does not change the kinetic energy of particles
The increased thermal energy of the medium increases the kinetic energy of particles
Correct answer: 4) The increased thermal energy of the medium increases the kinetic energy of particles
Explanation:
Higher the thermal energy in a medium: this raises the kinetic energy of its particles resulting in faster diffusion. The more heat there is, the more violent motion the particles perform the more collisions they experience, and the better the diffusion becomes as particles spread out and mix with others. Such a process plays a very significant role in biological and chemical systems, for example, in the transport of molecules, gases, and ions that determine the rate of chemical reactions and dynamics of systems.
Hence the correct answer is option 4) The increased thermal energy of the medium increases the kinetic energy of particles.
Q3. Which of the following has the maximum diffusion pressure?
Cell sap
Rainwater
Ice caps
All of these
Correct answer: 2) Rainwater
Explanation:
Pure water has a maximum diffusion pressure of 1236 atm, meaning it has the highest tendency to diffuse and move freely. When solutes are added, the diffusion pressure decreases, leading to a reduction in water potential. This works on the principle that during osmosis, the water moves from a region of higher diffusion pressure (pure water) to a region of lower diffusion pressure (solution).
Hence, the answer is option 2) Rainwater
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Frequently Asked Questions (FAQs)
The water potential of the plants refers to the measure of the potential energy of water, which would in turn affect its movement through the tissues of the plant. This becomes very important in understanding how water is taken up, moved, and lost on the basis that it has effects on net plant hydration and nutrient transport.
Transpiration is the loss of water vapour through the leaf from the stomata of the plant, cooling it, driving water uptake from roots, and facilitating the movement of nutrients and minerals in a plant.
Plants cope with water stress by shutting their stomata, thus preventing the loss of water, through developing deep or extensive roots, and by reducing water loss with the anatomical changes in their leaves.
These are drip irrigation, which efficiently saves a lot of water from wastage; sprinkler irrigation, suitable for large areas and undulating grounds; and flood irrigation, simple and of less cost on flat fields. Each has its advantages, depending on the availability of the water, type of crop, and condition of the field.