Plant Nutrition

Nutritional needs  Autotrophic does not mean autonomous…  plants need…  sun as an energy source  inorganic compounds as raw materials:  water (H2O)  CO 2  minerals

 Plants require these elements in relatively large amounts:  Think…. “C H O P S N K” Plus: Ca & Mg… We call these: Macronutrients

For what & from where?

Chlorophyll Why does magnesium deficiency cause the yellowing of leaves ?

Symptoms of Deficiencies  MOBILE- Some nutrients are more mobile than others… Symptoms show up in older parts first. Shunted to younger parts “preferentially”.  IMMOBILE- Symptoms show up in younger parts first. Get “stuck” in the older part…. Example: Mg Example: Fe

Water & mineral uptake  Water uptake  plants cannot extract all water from soil,only free water  osmosis  Cation uptake  cation uptake is aided by H+ secretion by root cells (proton pump) Campbell Animations

Fertilizers  “Organic” fertilizers  manure, compost, fishmeal  “Chemical” fertilizers  commercially manufactured  N-P-K (ex )  15% nitrogen  10% phosphorus  5% potassium

Nitrogen uptake  Nitrates  plants can only take up nitrate (NO 3 - )  Nitrogen cycle by bacteria  trace path of nitrogen fixation!

Nitrogen uptake continued… The rhizobium have an enzyme called “nitrogenase” N 2 + e H ATP  2NH 3 Very energy consuming: 32 ATP molecules just for 2 NH 3 !!! Contains “leghemoglobin” for high oxygen demands. Roots send out “flavinoids” which attract the rhizobium. Rhizobium, in turn, emit chemicals which stimulate root hair elongation with “infection threads for a portal of entry for the bacteria.

Another example of mutualistic symbiosis: Mycorrhizae Modified roots that are part fungus Fungi secrete growth factors & increase surface area for greater absorption for the plant…. Plant provides and stores food for the fungus.