lesson 4 Flashcards
macro and micronutrients
-autotrophs manufacture sugars
*utilize Co2, H2O
-additional nutrients required
*macronutrient: plant nutrients required in relatively large amounts
*micronutrient: plant nutrients required in relatively small amount
essential nutrients in plants
C, H, O, P, K, N, S, Ca, Fe, M, Cl, Cu, Zn, Mo, B, Mn
soil
highly weathered outer layer of the earths crust
-mix of sand, rocks, clay, silt, organic matter, humus, microorganisms, and minerals
-soil composition determines physical properties
soil structure
topsoil:
-most organic rich layer
-minerals and nutrients percolate down through the soil (in water)
subsoil:
-nutrients that have leached or “washed off” -rocks collect here
bedrock:
-water can collect here
water and mineral availability in soil
-about half of the soil volume is occupied by pores
*may be filled with air or water or both
*hydrogen bonds adhere water to soil particles and dissolve nutrients
-soil composition determines proportion of air water
-balance of sand, silt and clay
extracting nutrients from the soil
-nutrients must be in solution (ionic form)
-cations (+) bind tightly to soil particles
*plants utilize cation exchange
*pump H+ out of roots, facilitates release of cations
-anions (-) remain dissolved in pores
*subject to “leaching”
nutritional strategies: symbiosis with nitrogen-fixing bacteria
-N2 cant be utillized
*ammonia (NH3) and nitrate (NO3) are usable forms
*some prokaryotes can convert N2 into NH3 and NO3 (nitrogen fixation)
-legumes “invite” bacteria to form symbiotic relationships
=extensive signaling between host and Rhizobium bacteria
nutritional strategies: Symbiosis with mycorrhizae
-many plants (90%) have root symbiotic relationships with mycorrhizal fungi
*substantially expand surface area for nutrient uptake at roots
*fungi receive photosynthesized sugars
nutritional strategies: carnivorous plants
-strategy to obtain nutrients in low supply (nitrogen)
-carnivorous plants use modified leaves, hairs and trichomes to trap insects
*digested with special enzymes
nutritional strategies: parasitic plants
-parasitic plants exploit “host” for nutrients
-may be photosynthetic or non-photosynthetic
*dodder (nonphotosynthetic)
*indian pipe (nonphotosynthetic)
=sometimes called corpse plant or ghost plant
phytoermediation
-use of plants to clean polluted areas is called phytoremediation
*phytodegradation: toxin is broken down by the plant
*phytovolatilization: toxin released through stomata
*phytoaccumulation: toxin remains in plant tissue
plants defend themselves
-plants face similar threats as animals
*herbivores
*pathogens
=viruses, bacteria, fungi and nematodes
*extreme environments
*other plants
first line of defense
-physical barriers- dermal tissue
-epidermal cells have waxy covering
-suberin contains fatty acids
*protects against water loss, pathogen entry and seals wounds
-specialized structures
* trichomes, bark, thorns
invaders of dermal defense
*pathogens look for openings in dermal tissue
-dermal opening (stoma)
-mechanical damage/wounds
chemical defenses
-plant toxins
-defensins
-secondary metabolites
plant toxins
kill, weaken or repel herbivores
defensins
small peptides, antimicrobial, limit enzyme activity
secondary metabolites
-important for interacting with environment
-provide defense
-additional uses: medicine, flavorings, stimulants etc
allelopathic plants
-secrete chemicals to block seed germination or inhibit growth or nearby plants
-black walnut tree (juglans nigra)
mutualistic relationships with animals
-acacia trees and ants
-parasitoid wasps, caterpillars and leaves
wound response in tomato
static defenses
inducible defenses
wound response
static defenses
always present/ active, high energy demand
inducible defenses
active only when a threat is detected
wound response
-wounded leaved produce a signal molecule called systemin
-systemin moves throughout the plant
-cells with receptors produce jasmonic acid
-jasmonic acid turns on genes for proteinase inhibitor
-herbivores can’t digest plant
