Plant Nutrition

1
Plant Nutrition
2
Root and shoot systems of a pea seedling
3
The uptake of nutrients by a plant a review
4
Soils

• Soil quality is a major determinant of plant
  distribution and growth
• Topsoil is defined as a mixture of particles from
  rock, living organisms and humus (partially
  decayed organic material)
• Humus builds a crumbly soil that retains water.
  It is also a reservoir of mineral nutrients
• To be available to roots, minerals must be
  released from the soil particles into the soil
  solution.
• Anions not bound tightly to soil particles, are
  easily released.
• Cation exchange - roots add H to soil, which
  displaces cation minerals from soil particles
  into the soil solution

5
Nutrients (table p.721)

• Essential
• Macronutrients
• Micronutrients

6
The most common mineral deficiencies, as seen in
maize leaves
7
Nitrogen Cycle Reminder

• Nitrogen is often the mineral that has the
  greatest impact on plant growth
• In order for plants to absorb nitrogen, it must
  first be converted to NH4 (ammonium) or NO3-
  (nitrate)
• The main source of usable nitrogen for plants is
  the decomposition of humus by microbes.
  Nitrogen-fixing bacteria convert N2 to NH3 in the
  process of nitrogen fixation.
• Ammonifying bacteria convert NH3 (ammonia) to
  NH4. Nitrifying bacteria convert NH4 to NO3- in
  the process of nitrification.
• Nitrate can also be returned to the atmosphere
  (in the form of N2) by denitrifying bacteria in
  the process of denitrification

8
Soil bacteria and nitrogen nutrition of plants
Ammonifyingbacteria
9
Root nodules on legumes
10
Nutritional Adaptations

• Plant roots, especially on legumes, have
  swellings called nodules that are composed of
  cells containing nitrogen-fixing bacteria
  (mutualism)
• In mycorrhizae, the fungus benefits from a steady
  supply of sugar donated by the host plant. In
  return, the fungus increases the surface area for
  water uptake, selectively absorbs minerals that
  are taken up by the plant, and secretes
  substances that stimulate root growth and
  antibiotics that protect the plant from invading
  bacteria
• Mistletoe is a parasitic plant. It is able to
  photosynthesize, while some parasitic plants have
  minimal photosynthetic capability
• Epiphytes are not parasitic, they just grow on
  the surfaces of other plants rather than soil
• Carnivorous plants are photosynthetic, but they
  get some nitrogen and other minerals by digesting
  small animals (insects, etc.)

11
Nutritional Adaptations in Plants