Plant Plant NutritionNutrition

The uptake of nutrients occurs at both the roots and the leaves.

• Roots, through mycorrhizae and root hairs, absorb water and minerals from the soil.

• Carbon dioxide diffuses into leaves from the surrounding air through stomata.

• About About 80 - 85%80 - 85% of a herbaceous plant is water of a herbaceous plant is water

• Of the Of the 15-20%15-20% of a herbaceous plant that is of a herbaceous plant that is not water, about not water, about 95%95% of the dry weight is of the dry weight is organic substance and the remaining organic substance and the remaining 5%5% is is inorganic substance.inorganic substance.

• Most of the dry weight of a plant is the result Most of the dry weight of a plant is the result of uptake of COof uptake of CO22 through stomata in leaves. through stomata in leaves.

•Carbon, hydrogen, and oxygenCarbon, hydrogen, and oxygen are the most are the most abundant (an important) elements in the dry abundant (an important) elements in the dry weight of a plantweight of a plant

• Hydroponic cultures can be used to determine essential nutrients

• Air is bubbled into the solute to provide oxygen to root cells

Plants require 9 Plants require 9 macronutrients and at least macronutrients and at least 8 micronutrients8 micronutrients

•A particular chemical element is considered an essential nutrient if it is required for a plant to grow from a seed and complete the life cycle.

• Elements required by plants in relatively large quantities are macronutrients.

• Elements that plants need in very small amounts are micronutrients.

Plants require 9 Plants require 9 macronutrients and at least macronutrients and at least 8 micronutrients8 micronutrients

Macronutrients• Carbon, oxygen, hydrogen, nitrogen, sulfur, and phosphorus,

potassium, calcium, and magnesium.

• General Role: They are cofactors in enzymatic reactions.

ElementElement Taken in asTaken in as Needed forNeeded for

NitrogenNitrates; ammonium salts; as organic compounds (Nitrogen-fixing bacteria)

To make proteins and nucleic acids

Phosphorus Phosphates nucleic acids, phospholipids,

ATP, several coenzymes

Potassium Potassium salts

cofactors in protein synthesis; osmosis; operation of stomata

Magnesium Magnesium salts To make chlorophyll

Sulfur Sulphates For making proteins; for healthy root growth

CHNOPS KCaMg

CHNOPS KCaMg

N, P, K

Micronutrients.

• Iron, chlorine, copper, zinc, manganese, molybdenum, boron, and nickel.

• Required in relatively small amounts.

• Required for a plant to grow from a seed and complete its life cycle.

• Overdoses of them can be toxic

• FUNCTION:

• Most function as cofactors (catalytic function) of enzymatic reactions.• EX: Fe is a component in cytochromes

• proteins that function in the electron transfer chains of

chloroplasts and mitochondria.• While the requirement for these micronutrients is so modest

(only one atom of molybdenum for every 16 million hydrogen atoms in dry materials), a deficiency of a micronutrient can weaken or kill a plant.

Fe, Cl, Cu, Zn, Mn, Mo, B, Ni

• The symptoms of a mineral deficiency depend partly on the function of that nutrient in the plant.

• Ex: Mg deficiency, an ingredient of chlorophyll, causes yellowing of the leaves, or chlorosischlorosis.

The symptoms of a mineral deficiency depend on the function and mobility of the element

Healthy

K-deficient

PO4-deficient

N-deficient

Symptoms

Most Common

Nutritional Nutritional AdaptationsAdaptations

• Rhizobium.Nitrogen Fixation

•Plants cannot use nitrogen in the form of N2.

•It must first be converted to ammonium (NH4+) or

nitrate (NO3-).

Root nodule formationanimation

• The common agricultural practice of crop rotation exploits symbiotic nitrogen fixation.• One year a nonlegume crop such as corn is planted, and

the following year alfalfa or another legume is planted to restore the concentration of fixed soil nitrogen.

• Often, the legume crop is not harvested but is plowed under to decompose as “green manure.”

• To ensure the formation of nodules, the legume seeds may be soaked in a culture of the correct Rhizobium bacteria or dusted with bacterial spores before sowing.

• Mycorrhizae take two major forms: ectomycorrhizae, and endomycorrhizae.

• In ectomycorrhizae, the mycelium forms a dense sheath over the surface of the root and some hyphae grow into the cortex in extracellular spaces between root cells.

• In endomycorrhizae, the fungus makes extensive contact with the plant through branching of hyphae (arbuscles) that form invaginations in the host cells, increasing surface area for exchange of nutrients.

Almost all plant species produce mycorrhizae

Parasitic Plants

Indian pipe

Dodder

Mistletoe

Carnivorous Plants

supplement the plant's supply ofminerals…usually nitrogen

Sun Dew Video Clip

Attenborough Video Clip

Epiphytes• Plants that grow on

other plants but do not obtain nutrients from their hosts

• Derives its moisture & nutrients from the air and rain (sometimes from debris accumulating around it)

• Usually found in the temperate zone

The Role of Soil in Plant Nutrition• The texture and

chemical composition of soil are major factors determining what kinds of plants can grow well in a particular location.

FUNCTIONS 1) Support & anchorage  2) Supplies mineral nutrients  3) Supplies water  4) Allows gas exchange - especially 02 and CO2, but also ethylene 

• Inadequate drainage can dramatically impact survival of many plants.– Plants can suffocate if air spaces are

replaced by water.– Roots can also be attacked by molds

favored by the soaked soil.– High Clay content can also reduce

gas exchange

• Some plants are adapted to waterlogged soil.– For example, mangroves

• Some areas have become unfit for agriculture or wildlife as the result of human activities that contaminate the soil or groundwater with toxic heavy metals or organic pollutants.

• In place of costly and disruptive remediation technologies, such as removal and storage of contaminated soils, phytoremediation takes advantage of the remarkable abilities of some plant species to extract heavy metals and other pollutants from the soil.

• These are concentrated in the plant tissue where they can be harvested.

• For example, alpine pennycress (Thlaspi caerulescens) can accumulate zinc in its shoots at concentrations that are 300 times the level that most plants tolerate.