Plant NutritionBy Bridget Floyd, Neeloo Rahbari, and Amber Gallant

First of all….

NUTRITION!

Chemical Elements Original Propositions

• Aristotle: thought soil provided all of the necessary nutrients

• Jan Baptista van Helmont: after conducting an experiment he came to the conclusion that water provided the necessary nutrients

• Stephan Hales: postulated that plants are nourished by air

The correct answer…

Chemical Elements THEY WERE ALL CORRECT!!!

• The air, water and soil all have one thing in common…all are composed of chemical elements

Air: carbon dioxide, nitrogen and oxygen Water: hydrogen and oxygen Soil: nitrogen, oxygen, hydrogen,

magnesium, calcium, potassium,

Chemical Elements Key Terms

• Essential Elements: chemical elements that are required for a plant to sustain itself and therefore live and procreate Hydroponic culture: put plants in mineral

solutions in order to determine if a chemical is essential or not

• Able to identify 17 essential elements• Macronutrients: elements that a plant

requires in relatively large amounts Carbon, oxygen, hydrogen, nitrogen,

phosphorus and sulfur

Chemical Elements Key Terms Continued…• Micronutrients: elements that are

needed by plants in very small amounts

Chlorine, iron, manganese, boron, zinc, copper, nickel, molybdenum

Co-factors: non-protein helpers in enzymatic reactions

Chemical Elements Mineral Deficiencies depend on soil content/environment Depend on mobility of plant• nutrient moves freely, older plants

affected more• nutrient immobile, young plants

affected more common for nitrogen, phosphorus and

potassium

Chemical Elements Mineral Deficiencies continued… Treatment• Deficiency distinct enough for farmer

recognize • Add a bit of missing element• Moderate element so it doesn’t become

toxic to plant

Soil Components and Quality The texture and composition of soil

determine if particular plants can grow well in a certain locations

Texture is the soils general structure Porous vs. Compact Composition is its components Deficient vs. Toxic

Plants and Soil The interaction between plants and soil is very

crucial to the chemical cycles in ecosystems Topsoil is the richest soil that provides a strong

environment for plants to flourish in Humus is an important component of topsoil and is

formed by organic refuse. It builds a porous soil that allows for the aeration of the roots

Soil composition includes organic compounds as well as minerals

Plant roots can release organic acids, reinforcing the soil against erosion, and affecting soil composition and texture pH

Soil Particles and Ion Uptake Negatively charged ions (nitrate,

sulfate, phosphate) are bound tightly to negatively charged soil particles and are easily available for uptake by roots

Heavy rain causes the ions to drain away and become less available for uptake

Cation exchange is where mineral cations are available for absorption after being displaced by H+

Impact of soil on Agriculture Agriculture depletes the mineral content of

the soil Each year the soil fertility diminishes unless

fertilizer replaces the lost minerals (nitrogen, phosphorus and potassium)

The three goals of soil conservation are: prudent fertilization, irrigation, and prevention of erosion

Soil reclamation returns agricultural productivity to exhausted or damaged soil

Irrigation

Water is the limiting factor in plant growth.

Irrigation in an arid area makes the soil salty and unfertile

Topsoil Sustainable agriculture, a goal of soil

management is a commitment embracing a variety of conservation-minded environmentally safe and profitable farming methods.

Soil Reclamation A technique of soil reclamation is

phytoremediation, a biological technology that reclaims contaminated areas by using the ability of some plants to extract soil pollutants and concentrate them in portions of the plants that can be removed easily for safe disposal

Plant Nutritional Adaptations Nitrogen fixation: Swellings called nodules along a plant’s roots are

“infected” by nitrogen-fixing Rhizobium bacteria when a plant releases flavonoid molecules detected by the bacteria.

A specific strain of bacteria is able to absorb them, and activate nodulin genes, releasing Nod factors to signal the plant to begin the infection process.

The plant’s response involves activation of a set of early nodulin genes involving Calcium ions as second messengers.

The bacteria then assumes a bacteroid form within vesicles formed by the root.

Nitrogen Fixation…. continued

A protein called leghemoglobin acts as an oxygen buffer in this process, binding reversibly to oxygen and keeping the concentration of free O2 low.

Rhizobium can fix gaseous nitrogen and supply it as ammonium, a form that can be readily used by the plant.

The location of bacteroids inside living, nonphotosynthetic cells provides an anaerobic environment, favoring nitrogen fixation.

While the bacteria supplies nitrogen in a usable form, the plant supplies carbohydrates and other organic compounds to the bacteria.

Crop rotation!

Mycorrhizae Mycorrhizae are modified roots consisting

of mutualistic associations of fungi and roots.

The fungus benefits from sugar supplied by the plant and in return the fungus increases the surface area for water uptake and selectively absorbs minerals such as phosphate for the plant and secrete growth factors stimulating the roots.

Ectomycorrhizae In ectomycorrhizae, the mycelium

forms a dense mantle over the surface of the root, the fungae extending from the mantle into the soil and forming an extracellular space in the cortex of the root, facilitating nutrient exchange.

The hyphae of ectomycorrhizae are generally thicker and more branched.

Endomycorrhizae In endomycorrhizae, fine fungal hyphae

extend into the soil; they also extend into the root by digesting small patches of root membrane, forming tubes by invagination of the plasma membrane.

They form into densely branched structures called arbuscules, important sites of nutrient transfer between the cells and the fungi.

Hyphae may also form oval vesicles, which store food for the fungus.

This type of mycorrhizae is much more common than ectomycorrhizae; it occurs in about 85% of plant species.

Nonmutualistic Relationships An epiphyte, such as an orchid, may nourish

itself but grows on another plant, usually branches or trunks of trees. They absorb water and minerals from the rain.

Parasitic plants, such as mistletoe, absorb sugars and minerals from their hosts. Many have roots that can enter the host plant to obtain these nutrients.

Carnivorous plants are photosynthetic but obtain some nitrogen and minerals by killing and digesting insects. Traps are often modified leaves equipped with glands that secrete digestive juices.

Carnivorous Plants!• media.pearsoncmg.com%2Fbc%2Fbc_campbell_biology_7%2Fmedia%2

Fvideos%2FSunDewTrapPrey-V.html&h=4AQF5VjuI• http://www.youtube.com%2Fwatch%3Fv%3DVUWQFF0RJN4&h=4AQ

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humerus soil reclamation topsoil

micronutrients hydroponic culture texture

macronutrients humus hummus

nitrate oxygen potassium

calcium phosphate water (good old H2O!)

gaseous nitrogen

magnesium iron

cation exchange arbuscule ectomycorrhizae

endomycorrhizae Nod factors nodule

ectoplasmycorrhizae Rhizobium mineral deficiency