10 Questions
Hydrogen bonds provide a continuous intermolecular ______ between the water molecules from the leaf to the root.
attraction
The water column in the xylem lumen is driven out of a region with a higher ______ potential, i.e. from the root and the stem, to a region with a lower ______ potential.
water
The way in which water from soil enters roots, particularly to the root ______, is called "mechanism of water absorption".
xylem
Active absorption refers to the absorption of water by roots with the help of ______, generated by the root respiration.
ATP
Only ______% of total water absorption is carried out in active absorption process.
4
In active absorption, energy is ______.
required
In passive absorption, ______ energy is utilized.
metabolic
Most volume of water entering plants is by means of ______ absorption.
passive
The force for absorption of water is created at the ______ end.
leaf
As ______ proceeds, simultaneously water absorption also takes place to compensate the water loss from leaf end.
transpiration
Study Notes
Functions of Water in Plants
- Medium for biochemical reactions in cells, as many enzymes are dissolved in cell water
- Provides structural support through turgor pressure, giving many cells their shape
- Enables cell enlargement by providing the physical force needed to expand cells during growth
- Transports solutes between organs via xylem and phloem vessels
- Cools leaves during transpiration through evaporation
Diffusion
- Movement of molecules from a region of higher concentration to a region of lower concentration
- Occurs in gases, liquids, and solutes
- Factors influencing rate of diffusion:
- Temperature: increase in temperature leads to increase in rate of diffusion
- Pressure: rate of diffusion increases with increase in pressure
- Size and mass of diffusing substance: diffusion of solid is inversely proportional to size and mass of molecules and ions
- Density of diffusing substance: rate of diffusion is inversely proportional to density of the diffusion substance
- Density of the medium: rate of diffusion is slower if the medium is concentrated
Permeability
- Degree of diffusion of gases, liquids, and dissolved substances through a membrane
- Types of membranes based on permeability:
- Permeable membrane: allows free passage of solvent (water) and most dissolved substances
- Impermeable membrane: prevents entry of water, dissolved substances, and gases
- Semi-permeable membrane: permits movement of solvent molecules only
- Selectively or differentially permeable membrane: allows selective passage of solutes with solvent
Osmosis
- Special type of diffusion of a liquid through a semi-permeable membrane
- Solvent moves from a place of higher diffusion pressure to a place of lower diffusion pressure
- Importance in plants:
- Absorption of water by plants
- Cell-to-cell movement of water throughout the plant body
- Maintenance of rigidity of plant organs
- Growth of plant parts
- Resistance to drought and frost
- Movement of plants and plant parts
- Opening and closing of stomata
Plasmolysis
- Shrinkage of the protoplast of a living cell from its cell wall due to exosmosis under the influence of a hypertonic solution
Water Absorption in Plants
- Water is absorbed along with mineral solutes by root hairs
- Water moves deeper into root layers through two distinct pathways:
- Apoplast pathway: movement of water through intercellular spaces and cell walls
- Symplast pathway: movement of water through cytoplasmic strands and cell membranes
Ascension of Water Through Plant Vascular System
- Water flows from roots to shoot of the plant through xylem
- Cohesion-tension theory: hydrogen bonds provide continuous intermolecular attraction between water molecules from leaf to root
Mechanism of Water Absorption
- Active absorption: absorption of water by roots with the help of ATP, generated by root respiration
- Passive absorption: absorption of water without utilization of metabolic energy, occurs in rapidly transpiring plants during daytime
Learn about the functions of water in plants, including its role in biochemical reactions, structural support, and cell enlargement.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
