Review from earlier lecture:

Chemical Composition of Specific Seeds of Economic Importance   -  Chart -

Species                       Family               Nature of                                   Percent Content
                                                     Reserve tissue        Carbohydrate     Protein      Lipid
________________________________________________________________________
Maize                    Gramineae          Endosperm                51 - 74                10               5
(Zea mays)

Wheat                   Gramineae         Endosperm                 60-75                  13               2
 (Triticum vulgare)
Pea                         Legum                Cotyledon                  34-46                   20              2
 (Pisum sativum)
Peanut                                              Cotyledon                  12-23               20-30      40-50
 (Arachis hypogaea)
Soybean                                            Cotyledon                      14                   37             17
 (Glycine sp)
 

 Difference in Composition of Soluble Nitrogen - Chart -
            Aspartic Acid, Glutamic Acid, Glutamine, Asparagine

                          See Chart Handed Out in Class

 Parts of Seed - endosperm, scutellum, cotyledon,
                Changes in seeds during germination - Charts -
                Movement of various macromolecules

    Proteins converted to  Amines that move from storage organ to growing axis
    Carbohydrates converted to  glucose or sucrose that move from storage organ to growing axis
    Lipids converted to  Organic Acids that move from storage organ to growing axis
 
 
 

    Roots (radicle) will begin the uptake of inorganic nutrients (elements) from soil.
 

    Root structure - longitudinal section  REVIEW

    Mycorrhizal fungus

                                        "See handout from lecture"

   Inorganic elements present  - chart

  "See handout from lecture"

      How do you determine which inorganic nutrients are essential?

        Hydroponics          -      Water Culture or Sand

                            Macroelements - greater than 10 ug/g dry weight

                            Microelements - less than 10 ug/g dry weight
 

   Essential elements required for growth   -  chart

                                           "See handout from lecture"
 

                                    1.  Organic Molecules  Structure

                                    2. Energy storage

                                    3. Ionic form

                                    4. Redox reactions

Hoagland’s solution

Chelating Agents – form soluble complexes with insoluble ions - EDTA or DTPA

Influence of pH on uptake of minerals

                                             "See handout from lecture"

Relationship between growth and nutrient content

                 Chart: Deficiency zone, Adequate zone, Toxic zone, Critical concentration
 

                                            "See handout from lecture"

Mobile elements can move from older plant parts to new growth in plants that are deficient for that element.

Immobile elements can not move from older plant parts to new growth in plants that are deficient for that element.
 

Mobile                                 Immobile elements

N, K, Mg,                             Ca, S, Fe, B, Cu
P, Cl, Na,
Z, Mo
 
 
 
 

Nitrogen Metabolism –
Sources of nitrogne on Earth – NH₄,  NO₃,  NO₂

N₂ present in atmosphere but not available because it is inert.

Nitrogen Cycle – Five Parts:
 

                                    "See handout of nitrogen cycle from lecture"

Nitrogen fixation Converts  N₂ into NH₄

Abiotic – by lightning

Biotic – by living organisms -  nitrogenase is enzyme utilized

Free Living – Azotobacter and Clostridium, Cyanobacteria  - Anabeana, Nostoc
Symbiotically – legumes (beans, alfalfa)  contain nodules – rhizobium bacteria
 
 

Nitrification - Conversion of NH₃    to   NO₃ to NO₂
         (soil bacteria)  Plants may take up the ammonia.
      If  nitrates or  nitrites are taken up by plant, they can be  converted to ammonia
      by enzyme systems in plant cells, nitrate and nitrite reductase
 

Assimilation - Conversion of ammonia into amino acids and proteins
         (occurs in living cells)
 
 

Denitrification - Wasteful,  Conversion of nitrates and  nitrites back to  N₂

                   (soil bacteria carries out this process to acquire energy)
 

Ammonification -  Decomposition of organic nitrogen to ammonia
                               (bacteria and fungi)
 
 

What do  humans get from plants?

                         Energy Rich Molecules (food)
                         Oxygen
                         Biological Nitrogen