Essential NutrientsSoils

Nodules and Mycorrhizae

Plant Nutrition - Ch 37

Notes

• This is a short chapter - read it thoroughly.

• Pay attention (in all the chapters) to the “Concept Check” questions.

Essential Nutrients -

what do plants need?

One approach to“What are plants made of?” • Mostly water (except

woody parts)• Otherwise, mostly

carbohydrate, including cellulose

• But also phospolipids, nucleic acids, proteins, chlorophyll, other enzymes, coenzymes and cofactors

What is essential?

• Drying and burning plants only takes you so far.

• Plants incorporate minerals selectively, but the “filter” is imperfect.– This can be useful: “attack of

the metal-eating plants”

• How then to determine what’s essential?

Hydroponics

Hydroponics

• Essential Nutrient = plant cannot go from seed to seed without it.

Macronutrients

• Carbon• Oxygen• Hydrogen• Nitrogen• Sulfur• Phosphorus• Potassium• Calcium• Magnesium

..and Micronutrients

• Chlorine• Iron• Boron• Manganese• Zinc• Copper• Molybdenum• Nickel

• Often act as or with catalysts

• Cofactors - metal ions that enable enzymes

• Needed in very small quantities– Example - Mo

• Soil Origins• Soil Horizons• Soil Composition

– Sediment texture- clays vs. sands. Loam. – humus

SOILS

Cation Exchange

Nitrogen Fixation and Root Nodules

• Nitrogen is a limiting nutrient for much plant growth

• Atmospheric Nitrogen (N2) is unavailable to plants

• Plants rely on bacteria to fix Nitrogen into ammonia (NH4) and nitrate (NO3

-)• Some of these bacteria form symbiotic

relationships, living in nodules in plant roots (especially in legumes - peas, beans etc)

Nitrogen Cycle

N-fixing nodules on legume root

Mycorrhizae

• Symbiosis between plant roots and fungal myceliae

• Increases plant absorption of minerals greatly

• The fungus gets sugar, other nutrients• Occurs in 90% of plant species• Fungal species are specific to plant

species

Weirdos

Weirdos

Weirdos