Plant Nutrition

1
Plant Nutrition

• Chapter 37

2
Nutrient Uptake by Plants
3
17 Essential Elements

• required for a plant to complete its life cycle
• called mineral nutrients
• extracted from the soil in the form of inorganic
  ions
• 9 of the essential elements macronutrients
• needed in large amounts
• C, H, O, N, P, S, K, Ca, Mg
• 8 of the essential elements micronutrients
• needed in small amounts
• Cl, Fe, Mn, B, Zn, Cu, Ni, Mo
• function mainly as enzyme cofactors

4
Mineral Deficiency

• symptoms depend on
• role of nutrient
• mobility in plant
• ie if nutrients move freely, symptoms will show
  up 1st in older organs ( vice versa)
• deficiencies in N, P, K most common

5
Soil Quality

• important in determining plant distribution
  growth
• based on
• texture amounts of various sizes of soil
  particles
• composition organic inorganic chemical
  components

6
Topsoil

• most important for plant growth
• a mixture of particles derived from rock, living
  organisms, the remains of partially decayed
  organic material (humus)
• texture of topsoil depends on sizes of its
  particles
• composition topsoil has a high number variety
  of organisms
• bacteria, fungi, algae, protists, earthworms,
  nematodes, plant roots

7
Loams

• most fertile topsoils
• made up of roughly equal amounts of sand, silt,
  clay
• the fine particles help retain minerals water
• the coarse particles provide air spaces that
  contain oxygen needed by roots for cellular
  respiration

8
Humus

• important component of topsoil
• consists of decomposing organic material formed
  by the action of bacteria fungi on dead
  organisms, feces, fallen leaves, etc.
• prevents clay from packing tightly together
• builds a crumbly soil that retains water but is
  still porous enough to aerate roots
• reservoir of mineral nutrients

9
Soil Solution

• contains mineral ions released from the soil
  particles
• anions do not bind tightly to the negatively
  charged soil particles are easily released
• drawback easily leached in groundwater during
  heavy rain or irrigation
• cations become available after being displaced
  from the soil particles by H (cation exchange)
• less likely to be leached b/c bind tightly to
  soil particles

10
Agriculture Soil Conservation

• agriculture depletes mineral content of soil so
  fertilizers must be used to replace lost minerals
• crops use more water than natural vegetation so
  irrigation is needed
• prevention of topsoil erosion by water wind is
  also important methods include
• plant rows of trees as windbreaks
• terrace hillside crops
• cultivate in a contour pattern

11
Fertilizers

• commercial fertilizers are enriched in N, P, K
• minerals are available immediately but may not be
  retained by soil for long
• organic fertilizers include manure, fishmeal,
  compost
• release minerals gradually

12
Soil Reclamation Phytoremediation

• a biological, nondestructive technology that
  seeks to reclaim contaminated areas cheaply by
  using the ability of some plants to extract soil
  pollutants concentrate them in portions of the
  plant that can be easily removed for safe disposal

13
Nitrogen

• contributes most to plant growth
• required for proteins, nucleic acids,
  chlorophyll, etc.
• cannot be obtained from atmospheric nitrogen (N2)
• N2 must be converted to ammonium (NH4) or
  nitrate (NO3) for plants to absorb nitrogen
• The process of nitrogen fixation involves the
  conversion of N2 to NH3 (ammonia) by
  nitrogen-fixing bacteria
• NH3 can be converted to NH4 by picking up an H
  ion from the soil solution or to NO3 by
  nitrifying bacteria that oxidize NH3

14
Nutritional AdaptationsNitrogen Fixation

• involves a mutualistic relationship between roots
  the bacterium Rhizobium
• most commonly associated with legumes (ie peas,
  beans, peanuts, etc.)
• Roots contain swellings called nodules that are
  infected by Rhizobium
• Rhizobium are capable of fixing atmospheric
  nitrogen

15
Nutritional AdaptationsMycorrhizae

• mutualistic relationship between fungi plant
  roots
• plant provides fungus with sugars
• fungus provides plant with increased surface area
  for water absorption, selective absorption of P,
  growth factors that stimulate root growth,
  antibiotics that protect against pathogenic
  bacteria fungi
• This symbiosis may have been one of the
  evolutionary adaptations that made colonization
  of land possible
• 2 types ecto endomycorrhizae

16
Unusual Nutritional Adaptations

• epiphytes
• grow on other plants but nourish themselves
• absorb minerals water from rain thru leaves
• parasitic plants
• absorb sugars minerals from their living hosts
  via specialized roots
• carnivorous plants
• photosynthetic but obtain some N minerals by
  killing and digesting insects and other small
  animals