Chapter 37-Soil & Plant Nutrients

Explain how the presence of clay in soil helps prevent the leaching of mineral cations.

-Many minerals in soil (Ca2+, K+, Mg2+) adhere by electrical attraction to the negatively charged surfaces of clay particles. -This clay prevents the draining away of mineral nutrients during heavy rain or irrigation because finely divided particles provide so much surface area for binding materials. -Nitrates, phosphates, and sulfates (negatively charged) do not bind and tend to drain away. They are dissolved in the water, and absorbed by plants. One exception is phosphate, which binds to soil -Anions: leach out -Cations: resist leaching

Explain why plants cannot extract all of the water in soil.

-Some water adheres so tightly to hydrophilic soil particles that it cannot be extracted by plants. -This happens because the soil has electrically charged particles

The nine macronutrients required by plants include:

1) Carbon 2) Oxygen 3) Hydrogen 4) Nitrogen 5) Potassium 6) Calcium 7) Magnesium 8)Phosphorous 9) Sulfur

The eight micronutrients required by plants include:

1) Chlorine 2) Iron 3) Manganese 4) Boron 5) Zinc 6) Copper 7) Nickel 8) Molybdenum

Define the term essential element. Define the term limiting nutrient.

DEFINITIONS: •Essential Element: Element required by a plant to complete its life cycle. •Limiting Nutrient: Relatively availability in environment is less than plants need for it.

Explain why a symbiosis between a plant and a mycorrhizal fungus is considered to be mutualistic.

• Because the fungus gets a steady supply of sugar from the plant inversely, the fungus provides additional water and nutrients for the host plant.

Concept 37.1- Soil contains a living, complex ecosystem (a finite resource)

• In addition to climate, texture, and composition of soil are major factors in determining the distribution of plants.

o Parasitic plants

• Lives on other PLANTS and draws resources from that host. -Example: Mistletoe, Dodder, Indian pipe

o Carnivorous plants

• Obtains essential nutrients by eating animals, especially nitrogen from proteins. -Example: Pitcher plant, Venus flytraps

o Epiphytes

• Plants that grow on OTHER plants or hard surfaces: not rooted in soil -Example: Staghorn fern

Define soil texture and composition

• Soil Texture: relative amounts of various sizes of soils particles. The texture depends on the SIZE of the particles • Soil Composition: relative amounts of inorganic & organic components.

Explain how soil is formed.

• Soil is made up of particles derived from the breakdown of rocks (minerals) along with organic materials (humus). • As previously stated, soil's texture depends on the SIZE of the particles. Having different sized particles ultimately arises from the weathering the rocks. Water freezing in the crevices of rocks causes mechanical fractures, and weak acids in the soil break down chemically. When organisms penetrate the rock, the accelerate breakdown by chemical and mechanical means.

Name the components of topsoil (a.k.a "A" horizon).

• The remains of dead organisms and other organic material. -Definition of topsoil: A mixture of particles derived from rock, living organisms, and decaying organic material (humus).

Soil Horizons (layers)

• Visible in a vertical profile • "A" horizon is a mix of humus and minerals. -Humus consist of decomposing organic material -Prevents packing of smaller mineral particles and allows retention of water.

Name one modification for nutrition in each of the following groups of plants:

•Absorb water, minerals, and sometimes products of photosynthesis from their living hosts.

•Summarize the ecological role of each of the following groups of bacteria: o Ammonifying bacteria o Denitrifying bacteria o Nitrogen-fixing bacteria o Nitrifying bacteria

•Ammonifying bacteria: Bacteria convert N-containing organic material to NH4+ •Denitrifying bacteria: Bacteria convert NO3- to N2 •Nitrogen-fixing bacteria: Nitrogen fixation is the conversion of N2 to NH3. •Nitrifying bacteria: Bacteria convert NH4+ to NO3-

Define cation exchange, explain why it is necessary for plant nutrition, and describe how plants stimulate the process.

•Cation Exchange is a process that contributes to their uptake

Distinguish between ectomycorrhizae and arbuscular mycorrhizae.

•Ectomycorrhizae: A symbiotic fungus that form sheaths of hyphae over the surface of plant roots and also grows into extracellular spaces of the root cortex •Endomycorrhizae (Arbuscular mycorrhizae): A symbiotic fungus in which the fungus causes the invagination of the host cells plasma membrane

Distinguish between macronutrient and micronutrient.

•Macronutrient: required by plants in relatively LARGE amounts. •Micronutrient: required by plants in relatively SMALL amounts.

Define nitrogen fixation and write an overall equation representing the conversion of gaseous nitrogen to ammonia.

•Nitrogen fixation can be defined as bacteria converted into N2 from the atmosphere to NH3. • N2 + 8e- + 8H+ 16ATP 2NH3 + H2 + 16ADP + 16Pi

Concept 37.2: Plants require essential elements to complete their life cycle

•Plants derive most of their organic mass (biomass) from the CO2 in the air. •Also need soil nutrients like water and minerals

Explain how a legume protects its nitrogen-fixing bacteria from free oxygen and explain why this protection is necessary.

•The external layers of the roots are lignified, which limits gas exchange. Some root nodules appear reddish because of a molecule called leghemoglobin, which is an iron containing protein that binds reversibly to oxygen. This protein is an oxygen buffer, which reduces the concentration of free oxygen and thereby providing an anaerobic environment for nitrogen fixation while regulating the oxygen supply for the intense cellular respiration required to produce ATP for nitrogen fixation.

Describe the development of a root nodule in a legume.

•To understand this, one must define what a root nodule is. A root nodule is swellings along the root that have been "infected" by Rhizobium bacteria. •The development occurs in FOUR steps: 1) Chemical signals sent b/w roots and bacteria 2) Bacteria move into the coretx, form bacteroids: stimulate growth of cortex and pericycle cells. 3) TWO cell masses fuse forming a nodule. 4) Nodule develops vascular tissue.