**Historical Perspective and Nutrient Identification**:
– Justus von Liebig’s identification of nitrogen, potassium, and phosphorus importance in plant growth in 1840.
– Arnon and Stout’s demonstration of molybdenum’s essential role in tomato growth in 1939.
– Liebig’s law of the minimum stating plant growth limitation due to nutrient deficiency.
– Evolution of plant cultivation in non-soil media for research purposes.
**Nutrient Absorption and Uptake Processes**:
– Plants absorb essential elements from soil through roots and from air through leaves.
– Nutrient uptake facilitated by cation exchange through root hairs.
– Crucial role of the root structure in nutrient uptake rate.
– Casparian strip regulation of nutrient and water uptake in roots.
– Nutrient uptake mechanisms include simple diffusion, facilitated diffusion, and active transport.
**Nutrient Categories, Functions, and Sources**:
– Macronutrients like nitrogen, phosphorus, and potassium supplied in large amounts by soil.
– Macronutrients include calcium, magnesium, and sulfur.
– Micronutrients like iron, manganese, and boron sourced from soil.
– Importance of appropriate nutrient ratios for optimal plant growth.
– Soil and fertilizer as significant sources of essential nutrients for plants.
**Symbiotic Relationships and Nutrient Mobility**:
– Symbiotic relationships with microorganisms like rhizobia and mycorrhizal fungi.
– Roles of rhizobia in nitrogen fixation and mycorrhizal fungi in enhancing root surface area.
– Mobility of nutrients like nitrogen, phosphorus, potassium, calcium, and sulfur within plants.
– Differences in nutrient deficiency symptoms based on nutrient mobility.
**Nutrient Deficiency, Toxicity, and Interactions**:
– Symptoms and effects of macronutrient deficiencies like nitrogen, phosphorus, and potassium.
– Impact of micronutrient deficiencies like iron, zinc, and boron on plant growth.
– Effects of nutrient toxicity, particularly boron toxicity, on plant development.
– Interactions between nutrients like calcium, magnesium, copper, zinc, and iron.
– Influence of soil pH on nutrient availability and uptake by plants.
Plant nutrition is the study of the chemical elements and compounds necessary for plant growth and reproduction, plant metabolism and their external supply. In its absence the plant is unable to complete a normal life cycle, or that the element is part of some essential plant constituent or metabolite. This is in accordance with Justus von Liebig's law of the minimum. The total essential plant nutrients include seventeen different elements: carbon, oxygen and hydrogen which are absorbed from the air, whereas other nutrients including nitrogen are typically obtained from the soil (exceptions include some parasitic or carnivorous plants).
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Plants must obtain the following mineral nutrients from their growing medium:
- the macronutrients: nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), sulfur (S), magnesium (Mg), carbon (C), hydrogen (H), oxygen (O)
- the micronutrients (or trace minerals): iron (Fe), boron (B), chlorine (Cl), manganese (Mn), zinc (Zn), copper (Cu), molybdenum (Mo), nickel (Ni)
These elements stay beneath soil as salts, so plants absorb these elements as ions. The macronutrients are taken-up in larger quantities; hydrogen, oxygen, nitrogen and carbon contribute to over 95% of a plant's entire biomass on a dry matter weight basis. Micronutrients are present in plant tissue in quantities measured in parts per million, ranging from 0.1 to 200 ppm, or less than 0.02% dry weight.
Most soil conditions across the world can provide plants adapted to that climate and soil with sufficient nutrition for a complete life cycle, without the addition of nutrients as fertilizer. However, if the soil is cropped it is necessary to artificially modify soil fertility through the addition of fertilizer to promote vigorous growth and increase or sustain yield. This is done because, even with adequate water and light, nutrient deficiency can limit growth and crop yield.