Soil and Plant Nutrition

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The most common deficiencies are those of nitrogen, potassium, and phosphorus.

Slide 28

The most common mineral deficiencies, as seen in maize leaves

Healthy

Phosphate-deficient

Potassium-deficient

Nitrogen-deficient

Slide 29

Improving Plant Nutrition by Genetic Modification: Some Examples

Genetic engineering can improve plant nutrition and fertilizer usage:

Resistance to Aluminum Toxicity

Flood Tolerance

Smart Plants

Slide 30

Resistance to Aluminum Toxicity

Aluminum in acidic soils damages roots and greatly reduces crop yields.

The introduction of bacterial genes into plant genomes can cause plants to secrete acids that bind to and tie up aluminum.

Slide 31

Flood Tolerance

Waterlogged soils deprive roots of oxygen and cause buildup of ethanol and toxins.

The gene Submergence 1A-1 is responsible for submergence tolerance in flood-resistant rice.

Slide 32

Smart Plants

“Smart” plants inform the grower of a nutrient deficiency before damage has occurred.

A blue tinge indicates when these plants need phosphate-containing fertilizer.

Slide 33

Deficiency warnings from “smart” plants

No phosphorus

deficiency

Beginning

phosphorus

deficiency

Well-developed

phosphorus

deficiency

Slide 34

Plant nutrition often involves relationships with other organisms

Plants and soil microbes have a mutualistic relationship ++

Dead plants provide energy needed by soil-dwelling microorganisms.

Secretions from living roots support a wide variety of microbes in the near-root environment.

Slide 35

Soil Bacteria and Plant Nutrition

The layer of soil bound to the plant’s roots is the rhizosphere.

The rhizosphere has high microbial activity because of sugars, amino acids, and organic acids secreted by roots.

Slide 36

Rhizobacteria

Free-living rhizobacteria thrive in the rhizosphere, and some can enter roots.

Rhizobacteria can play several roles:

Produce hormones that stimulate plant growth

Produce antibiotics that protect roots from disease

Absorb toxic metals or make nutrients more available to roots.