Nutrition and Transport

Nutrients

95% of plant’s dry weight is carbon, hydrogen, and oxygen (carbohydrates, CO2 and water)

Minerals – provide proteins and nucleic acids Essential nutrients – had role, no substitute, and a

deficiency results in death. Macro and micronutrients according to concentration

Beneficial – required or enhances growth

soil

Mixture of mineral particles, decaying organic material, living organisms, air and water

Humus – decaying organic matter Mineral particles –

Sand – largest sized particles, water drains Silt - intermediate Clay – fine particles, not good drainage, - charge,

can retain + charged minerals. Loam – equal portions of silt, clay and sand, good

Soil profile

Vertical section of ground Horizons, parallel layers

A – uppermost, litter and humus B – inorganic nutrients leached form A C – weathered and shattered rock

Soil erosion – water and/or wind carry soil away to new location Loss of topsoil

Water and mineral uptake

Casparian strip – suberin and lignin border sides of root endodermal cells, force water to enter cells

Root hairs – allow water in at epidermal cells Minerals enter plants in ionic forms via

electrochemical gradient with ATP pump Root nodules – fix atmospheric nitrogen to NH4. Epiphytes – air plants, roots can absorb water or

in pockets at base of leaves.

Transport mechanisms

Xylem Tracheids – contain pits at ends that allow fluid to

flow from cell to cell Vessel elements – long, tubular, form hollow

pipeline Phloem

Sieve tube members - Companion cells – provide proteins to sieve-tube

members

Water transport

Root pressure – formed when water enters the root, usually at night Guttation – drops of water are forced out of vein endings

along edges of leaves

Cohesion-tension model of xylem transport Tension is created from the loss of water out of the leaves

(transpiration), draws water up from roots in vessels Cohesion – water molecules cling together Adhesion – water molecules cling to walls of vessel

elements Continuous water column

Stomata

Bordered by guard cells Potassium ions accumulate within guard

cells, water follows, stomata open Turgor pressure is increased in guard cells

Hydrogen ions accumulate outside guard cells

Stoma close when turgor pressure decreases K+ decreased and water leaves guard cells

Organic Nutrient Transport

Girdling – removing a strip of bark from around a tree

Pressure Flow Model of Phloem Transport Source (photosynthesis production – leaves) to

Sink (growth areas) – usually leaves to roots Sucrose is actively transported from leaves to

area of need, water follows per osmosis Sugar is used for respiration, water exits via

osmosis to xylem