Nutrient Balance NRES 406/606 Spring 2013

The study of how plants absorb and assimilate inorganic compounds is called Mineral Nutrition and it is specially important in agriculture and environmental protection

Higher plants are autotrophic organisms odchain/fullchain.gif

Higher plants are autotrophic organisms – Synthesize organic components out of the inorganic elements found in their surroundings odchain/fullchain.gif

Most of the nutrients plants need are taken up by the roots directly from the soil solution

C H O ~85% of plant dry matter is made of – C (Atmosphere) – H – O e_for_image_content/co2_molecule_720x400.gif

What are those inorganic elements?

Are all these elements equally important for plants?

What are those inorganic elements?

Essential Elements

Essential elements Those that have a clear physiological role. If plants receive all of these plus water and sunlight they will synthesize all the compounds needed.

Based on the relative abundance in the plant… Macronutrients – >1% – N,K, Ca, P,S, Mg Micronutrients (Trace elements) – <1% content/uploads/2012/01/quality_vs_quantity.jpg

Nutrient concentration is not constant among different plant structures. Why leaves?

Nutrient concentrations in the soils ultimately determine the acquisition and concentration in plants. Some soils have high concentration of specific elements, like heavy metals. – Au, Ag, Ni, Al Hg Accumulator plant In some cases, plants growing in soils with high concentration of a particular element can accumulate large concentration of that element without apparent side effects. Equisetum

The atmosphere is the mayor source of N – Biotic dinitrogen fixation – Deposition Some cations may come from particulates traveling form other regions or from industrial pollution – Na (sea salt in coastal regions) – Fe & P from Africa Nature

Nutrient recycling is the major source of soluble nutrients ion.jpg

Nutrient recycling is the major source of soluble nutrients ion.jpg Microbial Activity

How the element is found in the soil3. How does it change from 2 to 4 4. For that plants take up the element5. How does the element exist w/in the 8. Within the plant plant

Most of N in soil is found organically bound Microbial activity is required to make it available fro plants Element that plants need the most N deficiency rapidly affects plant growth chlorosis

P Integral component of plant cell Used in energy metabolism Stunt growth and yellow foliage S S and N are constituents of many proteins. Deficiency symptoms are very similar to those of N. ius/c498d5.jpg

6E E /$file/%23601%20legume%20lcp%20k% 20def.jpg K Inorganic form Found as free cation in plants (Osmotic potential) Activates many enzymes involved in photosynthesis

Mg Enzyme activation Synthesis of DNA and RNA Deficiency causes intervein chlorosis Ca Synthesis of cell wall Cell Division (mitotic spindle) ons/thumb/5/57/Chlorophyll_c2.svg/220px- Chlorophyll_c2.svg.png /PicsWeil/MagnesiumPoinsetti aRRW.jpg m_end_rot.JPG/220px-Blossom_end_rot.JPG

011/03/ hartman-rhodo-fe- deficiency-kaiser-h17-73.jpg Fe Component of enzymes involved in e - transport Intervenous chlorosis Why a chelate?

All micronutrients are found as inorganic compounds in the soil

N, P. S, Fe and Mg are directly involved in metabolic activities Ca and K are inorganic ions but are biological active ( osmotic potential) Leaves are the most common place of nutrient accumulation within plants (vacuole) Except Cl, all other micronutrients are stored as organic forms

Nutrient Uptake 1.Dissolved nutrients are taking in with water due to the continuous movement of water driven by transpiration SPAC

2.Proton pump: H + excreted out of cells affect the absorptivity of ions in the soil and release them into the soil solution. By releasing H + and HCO3- from the roots, plants promote ion exchange at the surface of clay particles. (Root Exudates) Nutrient Uptake

3. Weathering of the soil: Roots can release compounds that lower the pH breaking down soil particulates. s/chelate.jpg

Nutrient Balance Episode II

Nutrient uptake – Passive Following a gradient – Active Against a gradient

Ion Uptake into the cell Passive transport – Transport proteins Channels – (Selective) pores – Size and Density Carriers * – Substance being transported binds to the carrier – Conformational change – Dissociation

Ion Uptake into the cell Active transport – Energy depends on photosynthesis and respiration – ATP-ases function as proton pumps Electrochemical gradient – Present in plasmalemma and the tonoplast

Proton Pump

H + Pump

Electrochemical gradient

Uniports Cotransporters

Uniports: Integral proteins Charge Specific In the tonoplast these could be ion- specific. Low affinity

Cotransporters: Integral proteins Active transport Require H + pump High affinity One way & Two ways

Cotransporters

Response to Nutrient Supply Michaelis-Menten Uptake increase in response to supply until a maximum value is achieved (Imax) Km: nutrient concentration at which Imax/2 is reached

Km as a measure of Affinity Km is a measure of the capacity of the root to use nutrient at low concentrations. Km Affinity

H.A.S L.A.S

H.A.SL.A.S