Lecture #5 Plant Nutrition Flashcards
How do plants take up nutrients through their roots
Through mycorrhizae and root hairs they absorb water and minerals from the soil
How do plants take up nutrients through their leaves
Carbon dioxide diffuses into leaves from the surrounding air through the stomata
How many essential nutrients do plants need
17 they need nine macro nutrients and at least eight micro nutrients
What are macronutrients
Elements required by plants in relatively large quantities (carbon oxygen hydrogen nitrogen sulfur and phosphorus also potassium calcium and magnesium)
What are micro nutrients
elements that plants need in very small amounts for example iron chlorine copper zinc magnesium molybdenum boron and nickel)
What is chlorosis
It is the deficiency of magnesium a key component of chlorophyll which causes yellowing of the leaves. It can also be caused by iron deficiency
Where are mineral deficiency symptoms show me first
In the older tissues because the younger growing tissues have more drawing power
What is topsoil
A mixture of rock, living organisms and humus which is the residue of partially decayed organic material
What are horizons
Distinct layers of soil
Humic acid chemicals contain…
positive, negative and neutral sites: cation, an ionic attraction
What is humus
decomposing organic material formed by bacteria and fungi on dead organisms, feces, falling leaves and other organic refuse. It prevents clay from parking together and build a crumbly soil
Minerals especially ones with a positive charge such as potassium calcium, and magnesium, adhere by electrical attraction to the negatively charged surfaces of clay particles
Minerals that are negatively charged such as nitrate, phosphate, and sulfate, are usually not bound tightly to soil particles and thus tend to leach away quickly
what is cation exchange
When positively charged mineral ions are made available to the plant when hydrogen ions in the soil displays the mineral ions from the clay particles
What are the most fertile soil’s
Loam soil’s(equal amounts of sand , silt and clay) Because they have fine particles to provide a large surface area for retaining been rules and water which here to the particles. They also have enough coarse particles to provide air spaces that supply oxygen to the root for cell respiration
How can inadequate drainage impact survival of many plants
Plants can suffocate air spaces are replaced by water
Roots can also be attacked by molds favored by the soaked soil
Can the activities of organisms affect physical and chemical properties of the soil
Yes
What forms of nitrogen can plants use
Ammonium NH4+ or nitrate NO3- So the main source of nitrogen is the decomposition of humus by microbes including the bacteria and fungi
What is nitrogen fixation
A process where nitrogen fixing bacteria restock nitrogenous materials in the soil by converting N2 to NH3 (ammonia)
What is nitrogenase
an enzyme complex that catalyzes nitrogen fixation
How does NH3 (ammonia) turn into NH4+ (ammonium)?
It picks up another hydrogen ion in the soil solution
How is nitrate formed? (NO3-)
when ammonium (NH4+) is oxidized by nitrifying bacteria in the soil
what does symbiotic Nitrogen fixation result from?
Intricate interactions between routes and bacteria (mainly legume family)
What’s a nodule?
legumes root swellings composed of plant cells that contain nitrogen fixing bacteria of the genus rhizobium
What are bacteriods?
Form a rhizobium bacteria inside the nodule
Development of root nodules
1) Chemical signals from the route attract rhizobium, begin infection thread
2) bacteria penetrate the root cortex within the infection thread
3) cortex and pericycle fuse fuse after growth and form nodule
4) nodule grows, vascular tissue connects it to xylem and phloem
How is the process of nodule formation started
- Flavonoid signal travels from root to Rhizobium
- activates gene regulator (Nod D.)
- Nod. D binds to nod box, activated transcription of nod genes
- Nod genes produce metabolic enzymes
- Produces Nod factor, which travels to root and triggers infection thread
What are nod factors similar to
chitin
How can farmers ensure the formation of nodules
soak culture in rhizobium
How is the symbiotic relationship between a legume and nitrogen fixing bacteria mutualistic
Bacteria supply the legume with fixed nitrogen and the legume provides the bacteria with carbohydrates and other organic compounds
What are mycorrhizae
Modified roots consisting of symbiotic associations of fungi and roots (fungus roots)
how is mycorrhizae mutualistic
The fungus benefits from a hospital environment and steady supply of sugar
The plant benefits from phosphate and other minerals supplied to it and also growth factors that are secreted by the fungi to stimulate growth and also antibiotics that may help protect the plant from pathogenic bacteria and fungi in the soil
why do almost all plant species produce mycorrhizae
Because he made it possible for plants to colonize land in the first place and are Efficient at absorbing minerals
What are the two forms of mycorrhizae
ectomycorhizae: mycelium forms dense sheath over the surface of the root and some hyphae grow into the cortex in extracellular spaces between root cells (common in woody plants)
and
endomycorhizae: The fungus makes extensive contact with the plant through branching of hyphae (aburcles) that form invaginations in the host cells increasing surface area for exchange of nutrients
