Plant Nutrition

Nutritional needsAutotrophic does not mean autonomous…

plants need…

sun as an energy source

inorganic compounds as raw materials:

water (H2O)

CO2

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 waterosmosis

Cation uptakecation 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. 15-10-5)

15% nitrogen

10% phosphorus

5% potassium

Nitrogen uptakeNitrates

plants can only take up nitrate (NO3-)

Nitrogen cycle by bacteria

trace path of nitrogen fixation!

Nitrogen uptake continued…

The rhizobium have an enzyme called “nitrogenase”

N2 + e- + 6 H+ + 32 ATP 2NH3

Very energy consuming: 32 ATP molecules just for 2 NH3 !!!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:

MycorrhizaeModified 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.