Mineral Nutrition and Transport in Plants (Pages 198-217)
CHAPTER 10
FACTORS INVOLVED IN SOIL FORMATION

Weathering Process
Weathering is the gradual breakdown of rock in the
formation of soil
 Soils form from fragmented rock
 Weathering processes can be

 Biological

Growth of plant roots into cracks in the rock
 Chemical

Acid Rain
 Physical


Freezing and thawing of water in tiny cracks of the rock
Erosion (due to topography of land & gravity)
4 COMPONENTS OF SOIL
1.
Inorganic Mineral Particles
a)
b)
c)
d)
2.
Organic matter (Humus)
a)
b)
c)
3.
4.
Sand - .02mm – 2 mm
Silt - .002mm - .02 mm
Clay - particles smaller than .002 mm
Why isn’t gravel considered to be soil?
Litter (dead leaves and branches)
Dung (animal droppings)
Remains of dead plants, animals, and microorganisms
Water (Fills pore spaces)
Air (Fills pore spaces)
SOIL TYPES

Sandy Soils








Do not hold water and mineral ions well
Plants more susceptible to drought
More susceptible to mineral deficiencies
Provide support
Aeration
permeability
Silty Soils
Clay Soils




Low pH (attract cations, K+, Mg 2+)
Have poor drainage
Do not provide enough oxygen
Hold minerals and water well
LOAM SOIL

A loam
 is
an ideal agricultural soil
 Has optimal combination of different-sized soil
particles
 40% Sand
 40% Silt
 20% Clay
SOIL ORGANISMS

1 tsp of fertile
agricultural soil may
contain millions of
microorganism such as





Bacteria *most numerous
Fungi
Algae
Protozoa
Microscopic worms

Other soil organisms








Plant roots
Earthworms (make castings)
Insects
Ants (aerate soil, bury seeds)
Moles
Gophers
Snakes
Groundhogs
BENEFITS OF SOIL BACTERIA AND FUNGI
1.
2.
Decompose organic matter (Humus)
Release nutrients to be recycled to plant

3.
4.
Nutrient cycling – the process by which matter
cycles from the living world to the nonliving
physical environment and back again
Produce Ammonia (NH3-) Anions
Lower soil pH (makes it more acidic)
HYDROPONICS
A technique of growing plants in aerated water
– no soil!
 Minerals are dissolved into water solution
 Aerated by bubbles
 Soil-Free!
 Ideal for research of mineral usefulness

PLANTS REQUIRE 19 NUTRIENTS/ELEMENTS

Macronutrients (10)
 Element
that is required in large amounts for
normal plant growth

Micronutrients (9)
 Element
that is required in very small amounts for
normal plant growth
MACRONUTRIENTS (10)
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Carbon– (air) carbs, lipids, proteins, nucleic acid
Hydrogen– (water) carbs, lipids, proteins, nucleic acid
Oxygen– (water, air) carbs, lipids, proteins, nucleic acid
Nitrogen–* proteins, nucleic acids, chlorophyl
Potassium–* osmotic balance, stomata regulation
Calcium-* cell walls, membrane permeability
Magnesium-* Main component of chlorophyll
Phosphorus-* nucleic acids, phospholipids, ATP
Sulfur-* amino acids and vitamins
Silicon-*cell walls
* soil
MICRONUTRIENTS (9)
Chlorine
 Iron
 Boron
 Manganese
 Sodium
 Zinc
 Copper
 Nickel
 Molybdenum

TENSION-COHESION & ROOT PRESSURE

Tension-cohesion model
 Water
is pulled up the plant as result of a tension
produced at the top of the plant by the evaporative
pull of transpiration
 Transpiration is the loss of water vapor from the
aerial parts of plants
 Tension sucks water upward in xylem (like a straw)
from soil
See Figure 10-11 p. 212
TENSION-COHESION THEORY





The cohesion-tension theory describes how water moves
from the roots to the leaf.
Osmosis causes water to enter the xylem of roots from
the soil.
Due to the hydrogen bonding between the water
molecules, water forms a string of molecules as it moves
to the xylem.
Constant transpiration at the top of the leaf pull the
water molecules out of the plant.
The differences in water potentials and pressures cause
this fairly constant movement of water through the
plant.
Most water that plant
absorbs is transpired into
atmosphere.
Sugar molecules
manufactured in leaves
by photosynthesis are
transported in phloem
throughout plant,
including into roots.
Once inside roots, water
and minerals
are transported upward in
xylem to
stems, leaves, flowers,
fruits, and seeds.
Roots obtain
water and
dissolved
minerals from
soil.
Fig. 10-11, p. 212
PRESSURE-FLOW HYPOTHESIS

Sugar Translocation (the movement of sugar) in
phloem
 States
that dissolved sugar moves in phloem
because of a pressure gradient between the source
and the sink.
 Sugars move from source to sink
Source – an area of excess sugar supply (leaf)
 Sink – an area of storage (root, apical
meristem, fruit, seed)
