1. What does a plant need to ‘eat?’
CO2 (PS) + H2O (PS + hydraulic structure + TS)
and
essential elements
To synthesize all that it is:
cellulose and wall polymers
cytoplasm (including proteins)
membranes (lipids, fatty acids)
vitamins, co factors, ions and solutes
regulators
The source of all plants’ food is from
soil solution and atmosphere, where
required compounds are present in
VERY dilute quantities ---
plants have to scavenge, and concentrate
nutrients before building their bodies
Figure 38.1
An Early Experiment on the Role of Soil in Plant Nutrition.

2. Essential elements are required for
a plant to complete its life cycle.
They were discovered by
hydroponic culture and experiments
leaving proposed essential elements
out of the nutrient solution
Deficiency symptoms can be
categorized by showing up:
1) in lower (older) tissues first,
if so, the element is a mobile ion such as
K+, NO3-, and Mg+ and is transported
from older to younger tissue when the soil
does not provide enough for plant growth;
2) in upper (younger) tissues first,
if so, the element is an immobile ion such
as Ca++ and other divalent cations, once
incorporated into tissue, not easily extracted.
Figure 38.3
Hydroponics Is Used to Study Nutrient Deficiencies.

3. C HOPKNS CaFe Mg
a mnemonic for
remembering the
essential macronutrients
Fe is an exception

4. Table 38.1a
Essential Nutrients

5. Table 38.1b
Essential Nutrients

6. Table 38.1c
Essential Nutrients

7. cations are present in soil bound ionically to soil surface
= “cation bank”
pH of soil
determines
cation availability
acid soils are
cation-depleted
liming + fertilizer
restores nutrient
content of soil
anions do not
bind and thus are
easily lost from
the soil solution
during too much
rain/flooding
Cations often interact with negative
charges on the surface of clay
Organic
matter
Organic matter
Clay particle
Sand grain
Root hair
Clay particle
Figure 38.7
Cations Tend to Bind to Soil Particles; Anions Stay in Solution.
Clay particle
Sand grain
Anions usually dissolve in soil water;
they are readily available for
absorption by root hairs

8. Most nutrients are taken up by root hairs
Most nutrients are taken up by root hairs. Ions are dissolved in solution – the solution travels apoplastically through the cell walls to the endodermis (Casparian Strip) where it has to enter the symplast.

9. ATP H+ H+ ADP H+ H+ H+ H+ H+ H+ K+ H+ A-
The Nernst equation helps us know whether ion/solute distribution
is passive or active:
(Nernst potential) EN = RT X log Co [2.3RT ~ 59]
z F Ci
The Nernst equation states that at equilibrium, the difference
in concentration of an ion between two compartments
is balanced by the voltage difference
between the two compartments.
EN (Nernst potential) is the
membrane potential that would
allow passive distribution at a
give concentration gradient
EN predicts the concentration gradient
that would allow the membrane potential
to equal ENwith passive flux of that ion/solute
ATP H+ H+
ADP H+ H+ H+ H+ H+ H+ K+ H+ A-

10. Most plants are associated with fungi;
together fungal hyphae and roots make
up mycorrhizae. These structures:
increase the surface area of the nutrient gathering membranes;
assist in digesting organic materials in the soil for uptake into the plant;
increase water uptake
possibly ‘fertilize’ soil with CH2O from their host plant

11. Uptake of N is a special case, and in the case of legumes, is accomplished by
symbiosis with Rhizobium

12. Trapped
insect
Many plants obtain nutrition from digesting animals, and some plants parasitize others
Figure 38.18
Sundews Have Modified Leaves with Sticky Surfaces That Catch Insects.