Plant Nutrition SWES 316 Section H

What Do Plants Need to Grow? Van Helmont early 1600s –Grew a tree in 200# of soil for 5 years, gave it only water. After 5 yrs, he accounted for all but 2 oz of soil. Conclusion: water is the only essential nutrient for plants. Boyle mid 1600s –Plants contain “salts, spirits, earth, and oil”, which he thought were derived from water. Agreed with van Helmont.

What Do Plants Need to Grow? John Woodward 1700 –Grew spearmint in water from different sources (e.g. fresh, sewage). –Concluded that “earth”, not water, was the principal nutrient of vegetation. Jethro Tull 1700 –Believed that roots “eat” soil. Justus von Liebig early 1800s –C in plants comes from atmosphere, H and O come from water, other elements from soil.

What are Plants Made of?

Elements Found in Plants At least 50 chemical elements have been found in plants. However, most are not needed for plant growth. There are 17 chemical elements that are apparently required for all plants, and some more that are required for some plants. Plants are about 90% water and only 10% solids. Of the solids, only about 5-10% actually comes from the soil.

Essential Nutrient Elements An element is essential if it functions in some way in plant metabolism. Specifically, essential elements are those for which: –1) it is impossible for the plant to complete its life cycle without that element, –2) a deficiency can only be solved by supplying that element, and –3) the element is directly involved in the nutrition of the plant (and not in solving an environmental circumstance).

Essential Elements The above definition includes 17 elements required by all plants: "Macronutrients": C, H, O, N, P, K, S, Ca, Mg "Micronutrients": Fe, Mn, Zn, Cu, Mo, B, Cl, Ni Additional: Na, Si, V, Co

Essential Elements Organized by position in the periodic table: –Nonmetals: C, H, O, N, P, Cl, S, B –Alkali and alkaline earth metals: K, Mg, Ca –Transition metals: Mn, Fe, Ni, Cu, Zn, Mo

Representative Element Concentrations in Plants ElementConcentration (ppm) C N K P 2000 Ca 5000 Mg 2000 Fe 100 Zn 20 Mo 0.1

Nutrient Uptake (kg/ha/yr)

Nutrient Functions in Plants C, H, O Main structural components of plants NAmino acids, nucleic acids, proteins, chlorophyll Pphospholipids, energy transfer (ATP) Kosmotic regulation Sproteins

Nutrient Functions in Plants Castrengthens cell walls Mgchlorophyll Fe, Mn, enzyme activation, electron Cu, Zntransport Bcell division Closmotic regulation Monitrate reductase enzyme

Nutrient Functions in Plants Coessential for N fixation Voxidation reduction reactions Naessential for halophytes, osmotic regulation Sirequired for some grasses, strengthens cell walls Niessential for legumes, urease enzyme

How do nutrients get into plants?

Root Morphology Zone of most rapid nutrient uptake Slower nutrient uptake Cross-section of maturation zone

Nutrient Uptake Apoplasmic Transport –transport in the root “free space”. Is a “dead-end” except in the youngest part of the root. Symplasmic Transport - involves uptake across the plasma membrane: –Passive transport –Active transport

The Plant Cell

Nutrient Uptake Movement through the root to the xylem –Apoplasmic vs. Symplasmic –Apoplasmic in the youngest part of the root –Symplasmic in young and old parts of root Uptake into the Symplasm –Nutrients must cross plasma membrane –Active vs. Passive –Active: energy input needed –Passive: no energy input needed

Nutrient Uptake

Cell Structure

The Plant Cell

Plasma Membrane Function: to control the passage of water and solutes into and out of the cell Structure: –Phospholipid bilayer--hydrophilic outside, hydrophobic inside. When intact is impermeable to water and solutes –Embedded proteins: “channels” and “carriers” for passage of water and solutes. Under metabolic control.

The Plasma Membrane

Nutrient Uptake Definition: passage of nutrient ions or molecules across the plasma membrane. Nutrients thus taken up are then transported to the xylem for redistribution to sinks throughout the plant Active transport (uptake):requires direct input of energy (ATP) Passive transport (uptake): does not require energy

Apoplasmic vs. Symplasmic Most nutrients can be transported apoplasmically and symplasmically, and therefore can be taken up along the root axis. However, in many plant species, Ca is not transported symplasmically. –Therefore, only the youngest part of the root system takes up Ca. –This explains why some plants are especially susceptible to Ca deficiency.

Remobilization Remobilization is the movement of nutrients from one part of the plant to another. Some nutrients are mobile and some are immobile within plants. Remobilization from mature leaves to areas of new growth is essential to the life of the plant under conditions of limited nutrient availability (e.g wildland soils, poorly fertilized agricultural soils). Nutrient mobility affects where nutrient deficiencies are manifested.

Nitrogen and Corn

Ca Deficiency

Nutrient Mobility Mobility of a nutrient is often related to the function(s) of that nutrient in plants. Mobile nutrients: N, P, K, Mg, Cl Immobile: Ca, S, B, Fe, Mn, Cu, Mo, Zn

Nutrient Deficiencies Nutrient deficiency symptoms are often related to the function of that nutrient in plants. An "educated guess" regarding what nutrient is responsible for a particular deficiency can be made by considering the following: –position of deficiency on plant (old, young) –pattern of deficiency –color of deficiency

Deficiency Symptom Corn Older leaves Interveinal chlorosis Magnesium

Deficiency Symptom Tomato Fruit “Blossom end rot” Calcium

Deficiency Symptom Cabbage Older leaves Chlorosis Nitrogen

Deficiency Symptom Cotton Younger leaves Interveinal chlorosis Iron

Deficiency Symptom Alfalfa Older leaves Spotting, necrosis Potassium

Deficiency Symptom? Grapes All leaves Marginal burning, necrosis Salt, sodium toxicity