Plant water relations

• Water potential ranges from low to high (tension pressure)
• Drought triggers the production of ABA in roots, which moves to the shoot and leads to the closure of stomata
• Polarity of water is due to covalent bonds and opposite charges on molecules attracting each other, forming hydrogen bonds
• Water acts as a solvent, dissolving solutes to form solutions
• Latent heat is absorbed or released during a change in physical state without changing temperature
• Water potential (Ψw) is the sum of solute potential (Ψs), pressure potential (Ψp), and gravitational potential (Ψg)
• Water moves from a less negative to a more negative water potential, and from high water concentration to low water concentration
• Cell wall creates turgor pressure, influencing cell enlargement, gas exchange, transport, and rigidity
• Diffusion is the spontaneous movement of substances from higher to lower concentration, dominant in cell transport
• Osmosis is the diffusion of water across a selectively permeable membrane
• SPAC (Soil-Plant-Atmosphere Continuum) is the pathway for water movement from soil through plants to the atmosphere
• Transpiration, driven by the cohesion-tension theory, is the main driver of water movement in the xylem
• Cohesion of water molecules and tension create negative pressure, pulling water up the plant
• Air seeding and cavitation occur in xylem when tension is high, leading to embolism and vessel blockage
• Hydraulic conductance is facilitated through xylem, with tracheary elements like tracheids and vessel elements
• Surface tension, adhesion, and cohesion play roles in capillarity and water movement in plants
• Water flow through roots, stems, and leaves varies in resistance, with higher resistance in twigs and petioles
• Stomata regulate water loss through transpiration, influenced by factors like CO2 concentration, light, and temperature
• Transpiration rate is controlled by stomata conductance and water vapor pressure in intercellular airspaces
• Drought triggers the closure of stomata through the production of ABA in roots