chapter 37 Flashcards
What is an autotroph?
make their own food, usually through photosynthesis
what is a heterotroph?
absorb energy or consume nutrients from another source
Do plants “eat” minerals they obtain from the soil?
No, they absorb minerals to use IN photosynthesis
What is photosynthesis?
the process that converts sunlight, CO2, and water into food for the organism
Do all autotrophs photosynthesize?
No, some are chemoautotrophs (use inorganic compounds in environment)
What is chlorophyll?
photosynthethic material found in chloroplast, helps trap light energy
What light does photosynthesis use?
everything but green
Where does water enter in plants?
roots
how does the plant get CO2?
through their stomata
when does photosynthesis occur?
daytime! when the sun is out
what process occurs in plants at night?
respiration, have to conserve starch until they can do photosynthesis again
where do plants obtain most of their water and minerals?
upper part of the soil
how does soil benefit from living organisms?
living organisms aerates the soil and provides nutrients in their poo
what are the basic physical properties of soil?
texture and composition
what are the 3 different soil types?
largest=sand, medium=slit, smallest=clay
describe sand
better drainage but hard to retain water
describe clay
retains water but no aeration
why is air important?
animals, plants, and bacteria need to respire
how do rock particles get into soil?
mechanical weathering- water freezing in crevices of rock
chemical weathering- weak acid dissolves rock
both- organisms penetrate and grow in rock
what are soil horizons?
soil stratified into layers
what is topsoil?
consists of mineral particles, living organisms, and humus
what is loam?
the most fertile soil type, equal amounts of sand, clay, and slit
why is topsoil the most important for plant growth?
roots dont penetrate farther than topsoil and humus makes the topsoil fertile
what is soil type?
refers to the size ratio of the particles in a sample. depends on the parent rock type, climate (affects weathering), and present organisms
what is humus?
formed by decomposes, it is very rich and fertile soil. it improves soil structure and traps water
what is the b horizon? (subsoil)
contains much less organic matter than the A horizon and is less weathered
what is the c horizon? (parent rock)
composed of mainly partially broken-down rock. some of the rock served as “parent” material for minerals that later helped form the upper horizons
what caused the american dust bowl of the 1930s?
combination of drought and inappropriate farming
what are aquifers?
they are underground water reserves and are the primary source of irrigation water
what is land subsidence?
a gradual settling or sudden sinking of earth’s surface
what is salinization?
the addition of salts to the soil which makes it an unsuitable environment for plants
what is a solution to irrigation?
to use drip irrigation- the slow release of water to soil and plants from perforated plastic tubing placed directly at the root zone. this technique uses less water and reduces salinization
how do soils become depleted or nutrients?
irrigation leaches nutrients and crop harvesting takes them away
what is fertilization?
the addition of mineral nutrients to the oil
what chemical elements are fertilizers enriched with?
nitrogen, phosphorus, and potassium (NPK ratio)
what are the pros and cons of inorganic fertilizers?
pros: more and faster crop growth
cons: manufacture requires fossil fuels, eutrophication occurs
what is eutrophication?
excess nutrients go into bodies of water
what are the pros and cons of organic fertilizers?
pros: slow release of nutrients, improves soil texture, increase air spaces
cons: slow plant growth, needs to be manually spread out
how does pH affect the soil?
affects cation exhange and chemical form of minerals
what is the solution to adjusting soil pH?
there’s isnt one, its tricky to change soil pH so it’s best to plant crops best suited for that pH
what is contour tilling?
crops plants in circles, it helps slow water runoff and topsoil erosion
what is no-till agriculture?
narrow rows are plowed for seeds and fertilizer so the field is seeded with minimal disturbance to the soil
what is phytoremediation?
uses plants to remove contaminates from polluted soil types
What are some limitations of phytomediation?
contaminants could still get into water, affects herbivores
what are the 6 macronutrients?
carbon, oxygen, nitrogen, phosphorus, sulfur, hydrogen
What are the 8 micronutrients?
zinc chlorine iron manganese boron copper nickel and molybednum
what are micronutrients used for?
for coenzymes
whats phosphorus used for?
for nucleic acids
whats sulfur used for?
makes proteins
whats magnesium used for?
chlorophyll
whats iron used for?
making different compounds
a deficiency in a ______ nutrient will affect older leaves
mobile
a deficient of a less mobile nutrient will affect _____ leaves more
younger
what is the most common deficiency?
nitrogen deficiencies
what does a iron deficiency look like?
younger leaves yellowing
what does a nitrogen deficiency look like?
older leaves yellowing
what does a deficiency of magnesium look like?
yellowing of the leaves; chlorosis
what are smart plants?
plants that inform the grower of a nutrient deficiency before damage has occurred
what do living plant roots provide for soil?
secretions from roots support microbes
what do dead plant roots provide for soil?
nutrients and energy for microorganisms
what are detritivores?
they recycle organic matter
what is a rhizosphere?
the layer of soil closely surrounding the plants roots
what is rhizobacteria?
free-living bacteria living in the rhizosphere
what are endophytes
non-pathogenic bacteria that live between the cells of host plant tissues
what do rhizobacteria and endophytes do for the plant?
stimulates plant growth, protects roots from disease, absorbing toxins and increasing nutrient availability
why cant plants use atmospheric nitrogen?
the triple bond is too strong for the plant to break
what forms of introgen can plants absorb?
nitrate or ammonia
what is the nitrogen cycle?
describes the transformation of N2 and N2 compounds in nature
what is nitrogen fixation?
reduction of N2 gas by a stepwise addition of 3 pairs of hydrogen atoms
what is required for nitrogen fixation?
ATP, strong reducing agents, and nitrogenase
what is nitrogenase used for in nitrogen fixation?
to catalyze the reaction
How many ammonias are produced in nitrogen fixation?
2
How much ATP is needed for nitrogen fixation?
16
what are diazatrophs?
nitrogen-fixing bacteria
What is the symbiotic bacteria in legume plants? (pea plants)
rhizobium
what is the symbiotic bacteria in non-legume plants>
frankia
what is crop rotation?
a non-legume is alternated with a legume to restore the concentration of fixed nitrogen in the soil
what is mycorrhizae?
mutualistic association of fungi and roots
what is the benefit for mycorrhizae fungi?
fungi gets carbs from host plant
what is the benefit for host plants in mycorrhizae?
increased surface area for water uptake
growth secretions that promote branching
what are the two types of mycorrhizae?
ectomycorrhizae and arbuscular (endo) mycorrhizae
what is ectomycorrhizae?
they form a sheath OUTSIDE rootlets and penetrate root cells
what is arbuscular mycorrhizae?
hyphae extend into the root but not the plasma membrane, occur in 85% of plants
what are 3 adaptations that plants in nutritionally poor environments use other organisms to obtain N2 and nutrients in non-mutualistic ways?
epiphytes, parasitic, carnivorous
what are epiphytes?
plants that grow on top of other plants (vanilla)
what are parasitic plants?
absorb nutrients from hosts (mistletoe)
what are carnivorous plants?
capture small animals/insects
what are lobster pots?
can get in but not out
what are bladder traps?
exclusive to bladderworts, the prey is sucked in and a trap door closes behind them
what is the problem with nitrogenase?
it is very sensitive to oxygen and will deactivate. luckily most nitrogen-fixing bacteria are anaerobes
