Mineral Nutrition

1
Mineral Nutrition Botany 130 Lectures 19
2
Mineral nutrition

• What are the major nutrients needed by plants in
  addition to C, H, and O?
• What are the common symptoms of deficiency of N,
  P, K, and Fe?
• What symbioses are involved in plant nutrition?

3
What are the major nutrients needed by plants in
addition to C, H, and O?

• Nitrogen N (proteins and nucleic acids)
• Phosphorus P (respiration, photosynthesis and
  nucleic acids)
• Potassium K (used as a counterion)
• K comes from Kallium
• These are the three main ingredients of many
  fertilizers (NPK)

4
What are the major nutrients needed by plants in
addition to C, H, and O?

• There are three other nutrients that are present
  at 0.1 of dry weight or more
• Calcium, magnesium, and sulfur
• These six are the macronutrients
• N, P, K, Ca, Mg, S
• A number of other minerals are also essential but
  present at 0.01 or less

5
What are the major nutrients needed by plants in
addition to C, H, and O?

• In addition to dividing essential nutrients
  between macronutrients and micronutrients they
  can also be divided according to function
• N (CHONS, structural nutrients)
• P (PBSi, used as oxyanions)
• K (KNaMgCaMnCl, used as elemental ions)
• Fe (FeCuZnMo, used to carry electrons)

6
What are the symptoms of nutrient deficiency?

• Slower growth (for example phosphate)
• Yellow leaves (chlorosis) (nitrogen)
• Brown leaves (necrosis) (potassium)

7
Deficiency symptoms
Necrosis
Chlorosis
Interveinal necrosis
8
Nitrogen

• Most often limiting nutrient for land plants
• Deficiency chlorosis, especially lower leaves
• Excess delayed maturation
• High nitrogen fertilizer gives nice green lawns
  but delays ripening of tomatoes
• Sources, NO3- and NH4
• Nitrate reduction can consume a lot of energy

9
Nitrogen interactions
The most common form of N in the soil is nitrate.
As much as 25 of photosynthetic electron
transport can be used to reduce nitrate to
ammonia. Nitrogen fixation by Rhizobia is energy
intensive as is the Haber-Bosch process, the
method used to make commercial fertilizer.
Ammonia, NH3
Amino acids
Nitrite reductase
Nitrite, NO2-, (toxic)
Nitrate reductase
Nitrate, NO3-
10
Nitrogen

• N in plants functions in proteins and nucleic
  acids
• Bacteria can fix nitrogen
• Many plants have bacterial symbioses that provide
  ammonia to the plant
• Best-known symbiosis for N is legume/rhizobium
  symbiosis

11
(No Transcript)
12
Rhizobium (N)
13
Nitrogen interactions in plants
Nitrogen fixation
Ammonia, NH3
Amino acids
Nitrite reductase
N2 in the atmosphere
Nitrite, NO2-, (toxic)
Nitrate reductase
Nitrate, NO3-
14
Phosphorus

• Phosphate is unusual because it is taken up and
  used in the oxidized condition
• Most often likely to limit in lakes and streams
• Deficiency causes stunted, dark green plants,
  anthocyanin accumulation
• Phosphate absorption enhanced by symbiosis with a
  fungus - mycorrhizae

15
Vesicular-arbuscular mycorrhizae (P)
16
Nutrient cycles

• Biogeochemistry the study of the chemistry
  important in the interaction between the
  biosphere and the Earth
• Carbon cycle respiration ? photosynthesis
• Nitrogen cycle many complex interactions
  involving plants, animals, bacteria and chemical
  reactions

17
Nitrogen interactions
Nitrogen fixation
Ammonia, NH3
Nitrification by Nitrosomonas
Nitrite reductase
N2 in the atmosphere
Nitrite, NO2-, (toxic)
Nitrate reductase
Nitrobacter
Nitrate, NO3-
Denitrification (also makes lots of N2O, laughing
gas)