1
Plant Nutrition
(Chapter 38)
Plant nutrients
The process of photosynthesis results in the production of materials (oxygen and
sugars) that can be used by the plant for respiration, maintenance, growth, and
reproduction.
However, photosynthesis doesn’t provide all of the molecular building blocks that a
plant needs to sustain itself and grow.
In addition to CO2, water, and the products of photosynthesis (sugars), a typical
plant requires a number of inorganic nutrients that are often (but not always)
gathered from the soil.
These nutrients are typically dissolved in soil water and absorbed via specialized
root membrane proteins (membrane channels).
The inorganic nutrients that are important to plants are categorized as either
macronutrients (i.e., nutrients needed in relatively large amounts; Figure 2) or
micronutrients (i.e., nutrients needed in relatively small or even “trace” amounts;
Figure 3).
Most plants require 9 macronutrients (note that not all of these are primarily
acquired from the soil by a typical plant) ( Figure 2):
Carbon, oxygen, hydrogen— (principally acquired from atmosphere or from air
pockets in the soil) these 3 elements are found in all organic compounds.
Together they account for about 96% of a typical plant’s dry weight.
Nitrogen— (principally acquired from the soil) needed to produce amino acids,
proteins, nucleic acids, enzymes, etc.
, 2
Potassium— (principally acquired from the soil) needed for protein synthesis,
stomata functioning
Calcium— (principally acquired from the soil) needed as a component of cell
walls, enzyme catalyst, etc.
Magnesium— (principally acquired from the soil) forms the center of a
chlorophyll molecule
Phosphorus— (principally acquired from the soil) a component of ADP and ATP,
nucleic acids, etc.
Sulfur— (principally acquired from the soil) a component of amino acids and
proteins
Each of these 9 macronutrients can comprise from just below 1% to far more than
1% of the dry weight of a healthy plant.
For example, carbon and oxygen each account for about 45% of a typical plant’s dry
weight.
In addition to the foregoing 9 macronutrients, there are 8 micronutrients ( Figure
3).
iron, chlorine, copper, manganese, zinc, molybdenum, boron, and nickel.
Each micro- or “trace” nutrient constitutes several hundred parts per million or
less of the dry weight of a typical plant and typically these nutrients are acquired
from the soil.
Different plants can variously use macronutrients and micronutrients to carry out
their life processes and, plants that do not get the proper nutrients (be they
macro- or micro-nutrients) may not survive or they may become diseased.
Soil as a source of plant nutrients
The soil represents more to most plants than just an anchoring substrate.
And because most plants get macro- and micro-nutrients from the soil, soil
characteristics can affect plant survival and growth.
Plant Nutrition
(Chapter 38)
Plant nutrients
The process of photosynthesis results in the production of materials (oxygen and
sugars) that can be used by the plant for respiration, maintenance, growth, and
reproduction.
However, photosynthesis doesn’t provide all of the molecular building blocks that a
plant needs to sustain itself and grow.
In addition to CO2, water, and the products of photosynthesis (sugars), a typical
plant requires a number of inorganic nutrients that are often (but not always)
gathered from the soil.
These nutrients are typically dissolved in soil water and absorbed via specialized
root membrane proteins (membrane channels).
The inorganic nutrients that are important to plants are categorized as either
macronutrients (i.e., nutrients needed in relatively large amounts; Figure 2) or
micronutrients (i.e., nutrients needed in relatively small or even “trace” amounts;
Figure 3).
Most plants require 9 macronutrients (note that not all of these are primarily
acquired from the soil by a typical plant) ( Figure 2):
Carbon, oxygen, hydrogen— (principally acquired from atmosphere or from air
pockets in the soil) these 3 elements are found in all organic compounds.
Together they account for about 96% of a typical plant’s dry weight.
Nitrogen— (principally acquired from the soil) needed to produce amino acids,
proteins, nucleic acids, enzymes, etc.
, 2
Potassium— (principally acquired from the soil) needed for protein synthesis,
stomata functioning
Calcium— (principally acquired from the soil) needed as a component of cell
walls, enzyme catalyst, etc.
Magnesium— (principally acquired from the soil) forms the center of a
chlorophyll molecule
Phosphorus— (principally acquired from the soil) a component of ADP and ATP,
nucleic acids, etc.
Sulfur— (principally acquired from the soil) a component of amino acids and
proteins
Each of these 9 macronutrients can comprise from just below 1% to far more than
1% of the dry weight of a healthy plant.
For example, carbon and oxygen each account for about 45% of a typical plant’s dry
weight.
In addition to the foregoing 9 macronutrients, there are 8 micronutrients ( Figure
3).
iron, chlorine, copper, manganese, zinc, molybdenum, boron, and nickel.
Each micro- or “trace” nutrient constitutes several hundred parts per million or
less of the dry weight of a typical plant and typically these nutrients are acquired
from the soil.
Different plants can variously use macronutrients and micronutrients to carry out
their life processes and, plants that do not get the proper nutrients (be they
macro- or micro-nutrients) may not survive or they may become diseased.
Soil as a source of plant nutrients
The soil represents more to most plants than just an anchoring substrate.
And because most plants get macro- and micro-nutrients from the soil, soil
characteristics can affect plant survival and growth.
