Lab 3 - Lab 26 Lab Report Title Transpiration Introduction\/Hypothesis The amount of water needed daily by plants for the growth and maintenance of

Lab 3 - Lab 26 Lab Report Title Transpiration...

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“Lab # 26, Lab Report”. “Title: - Transpiration”. Introduction/Hypothesis : - The amount of water needed daily by plants for the growth and maintenance of tissues is small in comparison to the amount that is lost through the process of transpiration the evaporation of water from the plant surface and guttation the lost of liquids from the ends of vascular tissues at the margins of leaves. If this water is not replaced, the plant will wilt and may die. The transport of water up from the roots in the xylem is governed by differences in water potential the potential energy of water molecules. These differences account for water movement from cell to cell and over long distances in the plant.Gravity, pressure, and solute concentration all contribute to water potential, and water always moves from an area of high water potential to an area of low water potential see Lab 4 – Diffusion and Osmosis for a review of w . The movement itself is facilitated by osmosis, root pressure, and adhesion and cohesion of water molecules see Lecture 24 – Regulation and Transport in Plants for a review of water flow through a plant’s vascular tissues. The Overall Process Minerals actively transported into the root accumulate in the xylem, increasing solute concentration and therefore decreasing water potential. Water moves in by osmosis. As water enters the xylem, it forces fluid up the xylem due to hydrostatic root pressure. But the pressure can only move fluid a short distance. The most significant force moving the water and dissolved minerals in the xylem is upward pull as a result of transpiration, which creates tension. The “pull” on the water from transpiration results from the cohesion and adhesion of water molecules Figure 1 . Figure 1: - Transpiration model.

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