Transport in Plants

I. Overview

II. Absorption of water in Roots

III. Transport of xylem sap

IV.Control of transpiration

V. Transport of phloem sap

I. OverviewTransport of solutes into the root

Helps to create water movementSolutes= # of moleculesosmosis

Differences in water potential

Three components Total water potential (w) Pressure potential (positive/negative) p Solute potential (s)

w = p + sUnits are MPa

Water potential and movement

Osmotic movement of wateraquaporins

Absorption of water in Roots

Symplast = living tissueApoplast = cell wall space

Transport of xylem sapProperties of waterAdhesionCohesionTension

Root Pressure

Ascent of Sap

Transpiration-Cohesion-Tension Theory

Solar driven Water potential of air Relative humidity

Control of transpiration

Guard cells Photosynthesis-

transpiration compromise

Mechanism of guard cell opening

Environmental control and adaptations

Light (Blue light/Red light)

Water (drought)

Carbon dioxide (concentration in leaf/around leaf)

Adaptations

Xerophytes CAM plants Leaf hairs Sunken stomata

Xerophytic Adaptations

Transport of phloem sap

Source (photosynthetic tissue Sink (new leaves, seeds, roots Bidirectional flow Phloem Requires energy Transport of sugars (sucrose), amino

acids, potassium, and hormones

Munch Pressure Flow Hypothesis