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