HORT2060 midterm

Jan van Helmont

Learned that plants gain constituents from water

Jon Woodward

Plants obtain constituents from soil to support growth

De Saussure

Proposed that plants are composed of chemical elements obtained from water, soil, and air

German Sachs and Knops

First to grow plants without medium

W.F Gericke

Took laboratory experiments to commercial scale

Top Hydroponic Crops

tomatoes, cucumbers, lettuce, peppers

4 hubs of Greenhouses

Westland, Spain, Canada, Mexico

Soil factions

total, labile, and available

Three Rules for Essentiality

Elements must be needed by the plant to complete its life cycle, No other element can substitute for the element in question, The element must exert its effect directly on growth or metabolism and not by some indirect effect

Von Liebig’s Law of the Minimum

Plant yield will be limited by the most limiting growth or development factor, Increasing any other growth or development factor will not improve yield

Free Macronutrients

Carbon, Oxygen, Hydrogen

Big 3 Macronutrients

Nitrogen, Hydrogen, Potassium

Secondary Macronutrients

Calcium, Magnesium, Sulfur

Nutrient Solution

Essential elements must be dissolved in water and in proper form to be plant-available

Cation Exchange

Negative binding sites on soil colloids attract and bind positively charged cations

Cation Exchange Process

Root exudation and acidification of soil solution,Soil is negatively charged and attracts cations and bind to surface of soil, Protons are used by the plant

Cation Exchange Capacity

Soil acts as buffer for nutrients before it reaches plant

Mass Flow

Driven by transportation, Movement of water with nutrients through plant

Water potential(osmosis)

Moves from place of high potential to low

Xylem

Dead, Straw where water is transported up from roots, One way, Transports immobile nutrients

Phloem

living, sugars flow down from, leaves to roots/plant organs/fruits, Transports mobile nutrients

Symplastic route

Goes through living cells (in root cells)

Apoplastic route

Outside of living cells

Casparian strip

Where nutrients first goes into plant

Stomata

Where water diffuses from leaves

Passive Transport

Movement of solutes down their electrochemical gradient without direct energy input, Occurs through channels or simple diffusion, cations

Active Transport

Uses ATP hydrolysis to directly move ions against their electrochemical gradient, anions

Nutrient Uptake

Movement of solute through cell membrane

Mobile Elements

Nitrogen, Phosphorous, Potassium, Magnesium, Chlorine, Sodium

Immobile Nutrients

Calcium, Sulfur, Iron,

Immobile vs Mobile

Whether or not it can be moved in phloem

Nutrient Deficiencies

Soil solution or nutrient solution cannot provide enough essential elements for growth, pH is problematic, Other elements antagonize nutrient uptake, Environmental conditions antagonize uptake/translocation

Diagnosing Nutrient Deficiencies

What fertilizers are being used, What are pH and electrical conductivity (EC) values, Where did symptoms start

Localized

One part of leaf

Generalized

Entire part of leaf tissue

Necrotic

Dead leaf (dried out)

Marginal

Edge of leaf

Chlorosis

Yellowing

Interveinal

Between leaf veins

Mottling

Splotchy (not uniform discoloration)

Spots

spotting

Cupping

Margins are rolling over

Checked

More uniform discoloration

Brittle

Tissue breaks when touched

Soft

Leaf becomes soft

Dieback

Death happens on farthest margin and works inward

Stunted

Bad growth

Spindly

Etiolated (pale and drawn out)

New Leaf Affected

immobile nutrient

Old Leaf Affected

mobile nutrient

pH

Measure of acidity or basicity of a solution

as pH decrease

Hydrogen ion concentration increases

as pH increases

Hydrogen ion concentration decreases

Electrical conductivity (EC)

Measure of the strength of the nutrient solution (how salty), Does not tell what salts are in solution

Salt-based fertilizers

Are dissolved in water to provide macro- and micronutrients

Acids

Neutralize alkalinity, Proton donors

4 Acids

Citric Acid, Nitric Acid, Phosphoric Acid, and Sulfuric Acid

Citric Acid

Organic, expensive, Unlikely to use, Does not supply nutrient

Nitric Acid

Strong, Supplies nitrate

Phosphoric Acid

Weak, Supplies phosphorus

Sulfuric Acid

Strong, cheap, commonly used, supplies sulfate

Alkalinity

Measure of waters capability to neutralize acids, Buffering capacity of water, Concentration of soluble alkalides in solution

Alkalis

Dissolved bicarbonates

When hydrogen ion(acid) is added to water with alkalis(bicarbonates)

co2 and water is created

Buffers

stabilize solution pH

H2PO4

more present in water with lower pH

HPO42

more present in water with higher pH

H2PO4 + HPO42

perfect balance, 7.2 pH