BI111 Lecture Notes - Nutrient, Hydroponics, Nitrification

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Published on 20 Apr 2013
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Chapter 40 13-03-03 1:59 PM
Micronutrients: any mineral required by an organism in small trace
amounts
Macronutrients: minerals needed in large amounts.
Essential Nutrients: any of the essential amino acids, fatty acids, vitamins,
and minerals required in a plant.
Nitrification: a metabolic process in which certain soil bacteria convert
ammonia or ammonium ions into nitrites that are then converted by other
bacteria into nitrates, a form usable by plants.
40.1 Nutrition: Essential Materials
Hydroponics is Way to Study Plant Nutrition:
Hydroponics– an experimental method for identifying minerals absorbed into
plant tissues that were essential for growth
Scientist Sachs, measured various amounts of minerals and nutrients in
solutions, in which he grew plants.
By eliminating the elements on at a time, he determined the SIX essential
nutrients:
i. Nitrogen
ii. Calcium
iii. Magnesium
iv. Phosphorous
v. Sulfur
If you want to determine if a nutrient is essential, you include it in a
solution, and then transfer the plant to another solution that contains all
nutrients except the one you are testing… what happens?
Normal growth? The nutrient is not essential
You must remember to supply air bubbles to the roots because it is an
essential nutrient.
Carbon, hydrogen and oxygen are the only plant nutrients not considered
to be minerals
These nutrients are obtained from the air and water (the others are
obtained from the soil, or dissolved in water)
The amount of essential element adequate for one species may be toxic
for another
40.2 Soil
soil is a mixture od minerals, organic matter, air and water. Also contains
living organisms.
Soil is the source of water for most plants, and oxygen for cellular
respiration in the root cells.
The texture of the soil determines if the root systems have access to
sufficient water and dissolved oxygen… sand , silt and clay.
The relative proportions of the minerals determine the number and volume
of pores (air spaces). Also depends on the number of living organisms..
Humus holds a lot of water and provides a lot of vital nutrients.
Horizon A: Top Soil
Most biological activity occurs here and is the most fertile.
Most plant roots are concentrated in this layer
Horizon B: Sub Soil
Where the minerals are (including those needed by plants)… have
been washed down by rainfall
Mature tree roots extend to horizon B
Horizon C: Lowest layer
Is the parent material..
-regions where top soil is rich in humus are the most ideal for plants and
agriculture.
Uptake of water:
The soil solution contains water and dissolved substances
o Ionic interactions…
o Humus and clay are negatively charge and attract polar water
molecules (contain more water)
The proportion of water in the soil is proportional to the size of
particles and the ionic bond strength.
Sand has water move through it quickly (lots of air spaces)
Clay and humus contain more water, and adding more water is not
necessarily beneficial b/c you fill the air pockets and drown the
plant.
Cation Exchange:
Is passive– through transport proteins (facilitative diffusion)
Cations and anions (not equal in ratio)
Mg+, Ca+, K+ cannot easily enter the roots because the soil is
negatively charge (attraction between the soil and cations is called
adsorption)
Hydrogen ions in the soil, over-power the ion-soil bonds and replace
the cations (forming soil-hydrogen bonds) and freeing the cations.
o H+ come from carbonic acid (made by roots)
The free cations can now move freely into the roots
Anions are weakly bound to the soil and therefore move freely into
the root hairs
But they are also so weakly bound that they are susceptible to
leaching… water running through the soil, and bringing all the
anions down and away from the top soil.
40.3 Obtaining and Absorbing Nutrients
A. Acquisition of Nutrients
Roots continue to grow as long as the plant is living
o They grow more extensively when the soil is more abundant in
nutrients and water, etc
Root hairs are absorption structures that are associated with the uptake
of mineral ions and water.
Plant cell membranes have specific ion transport proteins that selectively
absorb ions from the soil.
Mycorrhizas: symbiotic associations between a fungus and the roots of a
plant… the fungi fixes nitrogen/ produces nitrogen… the roots can directly
uptake the nitrogen and nutrients from the fungus.

Document Summary

Micronutrients: any mineral required by an organism in small trace amounts. Essential nutrients: any of the essential amino acids, fatty acids, vitamins, and minerals required in a plant. Nitrification: a metabolic process in which certain soil bacteria convert ammonia or ammonium ions into nitrites that are then converted by other bacteria into nitrates, a form usable by plants. Hydroponics an experimental method for identifying minerals absorbed into plant tissues that were essential for growth. Scientist sachs, measured various amounts of minerals and nutrients in solutions, in which he grew plants. By eliminating the elements on at a time, he determined the six essential nutrients: nitrogen, calcium, magnesium, phosphorous, sulfur. You must remember to supply air bubbles to the roots because it is an essential nutrient. Carbon, hydrogen and oxygen are the only plant nutrients not considered to be minerals: these nutrients are obtained from the air and water (the others are obtained from the soil, or dissolved in water)