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The process responsible for facilitating loss of water in liquid form from the tip of grass blades at night and in early morning is:
Water loss as vapor through stomata is Transpiration (pull). Water loss as liquid droplets through hydathodes at night/dawn is Guttation, driven entirely by positive hydrostatic ROOT PRESSURE. Mark Root pressure (Option 2) in 5 seconds!
The loss of water in liquid form (as droplets) through specialized unclosable pores called hydathodes situated at the margins and vein-endings of leaves is termed guttation.
Guttation typically occurs during the night and early morning when transpiration is virtually nil (high atmospheric humidity, closed stomata), but active mineral absorption by root cells continues unabated.
Active transport of mineral ions into the root vascular bundle lowers water potential, causing water to flow into xylem by osmosis. This builds up a positive hydrostatic pressure termed root pressure, which pushes water columns upwards and forces liquid droplets out of hydathodes.
Transpiration is loss of water vapor driven by negative suction pull; Imbibition is adsorption by dry colloids; Plasmolysis is cell shrinkage in hypertonic medium. Only root pressure facilitates guttation.
Diagnose every choice: Know exactly why the right option works and why distractors fail.
Incorrect; transpiration involves water loss in the form of water vapor through stomata driven by a negative tension pull, not liquid droplets.
Factually exact; positive root pressure pushes water out through hydathodes as liquid droplets when transpiration is absent.
Incorrect; imbibition is water adsorption by dry seed coats and cell walls without forming a solution.
Incorrect; plasmolysis is the shrinkage of protoplast from cell wall in hypertonic external solutions.
Transpiration = Vapor loss (negative pull). Dew = Condensation of atmospheric moisture. Guttation = Liquid water exudation from hydathodes driven by positive ROOT PRESSURE.
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