Chemistry Research

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Chemistry Research

CHAPTER 32
The tallest tree is the Redwood (Sequoia sempervirens) approx 110 m
The tallest Angiosperm is the Australian Eucalyptus regnans
Water Uptake and transport (Fig. 32.1)
= water is essential because: transport solute, cool the body, photosynthesis and Turgor pressure
Osmosis- movement of H2) through a semi-impermeable membrane
Osmotic potential ( o)-depend on dissolve solute: Hi concentration means more negative o.
Isoosmotic-two solution with same o; Hypoosmotic- solution that has a less negative o(more +)
Turgor Pressure -hydraulic pressure result from water up take, cell turgid; analog to air pressure in a tire
Water Potential ( )-Overall tendency of a solution or cell to take up water from pure water solution.
= o + P, P is positive and is measured in MegaPascal (MPa); loss in P means the plant will wilt.
MINERAL UPTAKE
= Mineral and ions transported across membranes by protein: Pumps and Ion channel & Symport
= Use both Facilitated (low K outside cell) and Active transport (depend on Respiration).
= Plant do not have a Na/K pump but a H pump (generate membrane potential/ gradient).
= Ion transport changes Electric potential of membrane (-120mV- can be measure by electrodes)
= The traffic of ions into/out of cell can be measure by Patch clamping technique.
Apoplast & Symplast
= Water moves into the Stele (more - ) from the cortex (less - ) from the soil (more less - )
= Mineral move by Mass flow or diffusion/Active transport (via Membrane Protein)
Apoplast-movement through cell wall and intercellular space; it is continuous
Symplast- movement through the cell and b/w cell via plasmodesmata; continuous but regulated
= H2O from the Apoplast stops at the Endodermis (Stele); have Casparian strips -made of suberin
= Strip separate Apoplast of the cortex from the Apoplast of the stele (periclcle)
= Membrane protein enable enables selective mineral uptake and uptake rate.
Transfer cells -in pericycle, transport minerals from cytoplasm back into the apoplast (MP/Mit, SA, rate)
TRANSPORT IN XYLEM
Model 1-pumping cells stem; ruled out by Eduard Strasburger exp-use poison pitric acid; Stop in the leaf
= Exp. demonstrate: (1) pumping cell not responsible for uptake (2) leaves important (3) root not involve
Model 2- Capillary action ruled out because capillary action cannot support 110 m tree (40 cm)
Model 3-  root pressure-based on more - in xylem & less neg in root; support by guttation
Guttation- the removal of H2O through the leave...

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