Chapter 36 Flashcards
Nutritional requirements of plants
Essential nutrients
Macronutrients
Micronutrients
Essential nutrient
Element or compound required for normal growth and production
Essential nutrients for plants
3 essential elements: C,H, O (96% of dry mass)
14 mineral nutrients: elements found in soil
Macronutrients
elements in soil that plants require in large quantities; used to make nucleic acids, phospholipids and proteins
Micronutrients
Required in small quantities; function as cofactors of a specific enzyme
Limiting nutrients
Nutrients where their availability limits plant growth
Nitrogen, phosphorus, potassium
Hydroponic growth
Method used to study effects of nutritional deficiencies
Method: Plant is grown in liquid without soil with availability of nutrients controlled
Weathering
Forces applied by rain, water, wind; begins process of breaking down solid rock into soil
Humus
decaying organic matter
improves soil fertility, water retention, CEC (cation exchange capacity), nutrient availability, and soil health of the soil
How does soil texture effect the soil
Effects penetration of roots, ability to hold H20 and availability of O2
Mature soils
Mixture of organic and inorganic compounds
Loams
The best soil as it contains humus and has a good mixture of texture
Factors affecting nutrient availability
Anions
Cations
How does anions affect nutrient availability
High concentrations of anions like nitrate, sulfate, and phosphate increase plant growth while low concentration can limit it
Cause leaching due to anions not being taken up by plants or absorbed onto soil particles which can cause nutrient loss
Leaching
Loss of nutrients via movement of water through soil
How does cation exchange affect nutrient availability
- Cation exchange helps release positively charged nutrients to be absorbed by plants which increases the soil’s ability to retain and supply essential nutrients
If too many cations are absorbed the ph increases, which means more acidity which can cause leaching
Nutrient uptake
the amount of each nutrient required for the crop to complete its life cycle at a given yield level
Zone of maturation
Zone where nutrient uptake occurs
How does epidermis and root hair affect nutrient uptake
Increase surface area available for nutrient and water absorption
Zone of depletion in soil
Form due to the uptake of soil resources, primarily mineral nutrients and water
Proton pumps
Plasma membrane of root hair and epidermis cells contain proton pumps
Move nutrients into cell against the concentration gradient
Establishes electrochemical gradient that makes it possible for roots to absorb cations and anions
How do cations enter root hairs
Via ion channels (diffusion)
Require ATP
How does the electrochemical gradient established by proton pumps assist plant roots
Makes it possible for plant roots to absorb cations via ion channels & anions via symporters
How do anions enter root hairs
via cotransporters (symporters) against concentration gradient
Require ATP
Mycorrhizal fungi
80% of plants have this fungi
providing increased water and nutrient absorption capabilities, and phosphorus to plants and receive sugar in return
Symbiotic mutualism
Both organisms benefit
Nitrogen fixation
Bacteria absorbs N2 from atmosphere, converts it to ammonia, nitrates and nitrites which plants can absorb
Requires specialized enzymes and cofactors such as nitrogenase and ATP
Nitrogen fixation bacteria
Takes up residence inside plant root cells
Rhizobium
Bacteria that lives inside pea roots (legumes) and fixes nitrogen from the soil
Helps colonize Legume plant roots to form root nodules and in return gains carbohydrates and protection from the plant whose roots they inhabit.
Root nodules
Contain nitrogen fixing-rhizobia (provide plant with ammonia in return for sugar & protection)
Flavonoids
Compounds produced by the plants that attract rhizobia bacteria
Epiphytes
Nutritional Adaptations of Plant
Plant or plant like organism that grow in the absence of soil on leaves or branches of other plants
Absorb nutrients through leaves from air and rain (mosses, ferns, tropical plants)
Parasites
Nutritional adaptation of plants
Live on/in another plant and absorb nutrients from the host using haustoria
Nutritional adaptation of carnivorous plants
Used modified leaves to trap and kill insects and other animals - absorb prey’s nutrients
Use carnivory to supplement when low nitrogen availability in soil
What makes up most of the mass of a plant
CO2 and oxygen
How do plants influence the uptake of cations such as magnesium involving cation exchange?
cation exchange is driven by the release of CO2 by root cells because CO reacts with H2O in soil to produce carbonic acid, which releases protons.
How do proton pumps impact potassium uptake?
decrease positive charge within the cell to attract potassium ions
A molecule binds and blocks a potassium channel in a plant cell membrane. What would be its effects?
Potassium uptake would be blocked since potassium ions enter cells through facilitated diffusion.
Why is the presence of clay particles important in soil?
The negative charges on clay bind to positively charged ions and prevent them from leaching.
Where does most nutrient uptake occur in roots?
in root hairs, in the zone of maturation
Cation exchange
CO2 is released into the soil by root hairs, binds to H20 and releases carbonate and hydrogen.
Then it binds to cations and brings them into the root
