Transcript “nitro-gen fixing bacteria” which takes N 2 and

PLANT NUTRITION
Table 37.1 Essential Nutrients in Plants
Figure 37.3 Magnesium deficiency in a tomato plant
Figure 37.5 Soil horizons
Figure 37.6 The availability of soil water and minerals
Nitrogen is a key plant nutrient
1. Nitrogen gas can be fixed from the air by special “nitrogen fixing bacteria” which takes N2 and converts it to
NH3 using an enzyme called nitrogenase.
2. The ammonia picks up a H+ and forms ammonium
3. Organic material being decayed also be converted to
ammonium
4. Nitrifying bacteria convert the ammonium to nitrate
ions
5. Nitrate ions can then be absorbed by the plant
6. Nitrate is converted back to ammonium for use in
amino acids, proteins, etc.
Figure 37.9 The role of soil bacteria in the nitrogen nutrition of plants (Layer 3)
Figure 37.10x Nodules
Figure 37.11 Development of a soybean root nodule
Figure 37.13 Molecular biology of root nodule formation
Mycorrhizae also help with plant nutrition
Def:
FUNGUS and the root
So a mutualistic association and symbiotic
The fungus gets the sugar from the plant and
the root obtains increase surface area for
absorption of water and especially phosphate.
Fungi also secretes growth factors to stimulate
root growth and branching.
Fungi also produces antibiotics to help plant
avoid pathogenic bacteria and fungi in soil.
Evolutionary Adaptations
1. Mycorrhizae may have helped plant colonize land
a) early soil was poor so fungus helped to gain nutrients
and gain an advantage
b) nutrient poor soils, when planted, have lots of
mycorrhizae associated with these plants.
c) present on most plants.