plant stress Flashcards
what is plant stress
prevents plants from growing to their full potential
how do plants respond to stress
plant stress responses describe characteristics observed when plants detect stress, not all plants respond to stress in the same way.
understanding the plant’s stress is an important and challenging topic
what is abiotic stress caused by
It caused by non-living factors
what are some examples of abiotic stress
nutrient stress, salt stress, cold stress, heat stress
how does salt cause plant stress
salts in soil deprive plants of water and dissolved nutrients.
plant roots have a low water conc. which attracts water into the plant (osmosis)
desolved salts increase osmotic pressure of soil solution less water from the soil will enter roots
if soil solution becomes to conc. the plants die even though there’s an adequate amount of water and dissolved nutrients
how does low-temperature cause plant stress
low temp results in slow plant growth and development
when temp goes below 0*C freezing damage can occur
what happens when freezing damage occurs
the water within the cell will form crystals and when the temp rises and ice melts the cell contents leak out killing the cell
what are the characteristics of a frost-damaged plant
they will appear dark green and water-soaked at first, later becoming blackened and necrotic. in dry conditions, the tissue may appear white as the water from the broken cell evaporates
how do perennials survive the low temperatures
perennial species will undergo change to become dormant for the winter. how ever perennials can still be damaged by low temperatures
what species is winter burn noticeable in
it is noticeable in ever grees
what is winter burn
it is an injury that occurs when the absorption of water by the roots can’t keep up with the amount of moisture lost by the transportation
what conditions does winter burn occur in
it occurs mostly on sunny days especially when it is windy and when the soil water is frozen and the plant cat absorb it, or is water is short in supply
what does winter burn look like
the injury appears as brown leaf margins or needle tips at the onset of the first period of warm water
what happens if the temperature becomes too high for the plant
the cell proteins coagulate (cook) and the plant cell dies
how is wilting caused
during warm weather, if plants are unable to take up moisture they will wilt and die because the net assimilation rate is negative (photosynthetic gains are less then respiration losses)
how do plants cope with wilting
to cope with the loss of moisture the stomata will close. this results in the plants not being able to perform photosynthesis
what is the stomata
they are openings in plants that allow for the movement of gases. vaporized water leaves through the stomata and CO2 enters.
when is the stomata (of most plants) open
they are open during the day and closed at night
what is the function of guard cells
it’s the cell that surrounds the stomata and opens and closes them
where are the guard cells located
they are present in pairs in the outer skin of a plant most are on the underside of the leaf. but can also be present in stems, petals, etc… but NOT the roots
how does turgor pressure work
guard cells respond to turgor pressure (water pressure) to regulate the opening. this helps regulate the water.
ex. if the plant is wilted, water pressure is low and the guard cells will then be closed. this is beneficial because the plant won’t lose the little water it has
what is the cuticle of the leaf structure
it’s the outer surface of the leaf. there may be a waxy cuticle to reduce moisture loss. the thickness varies among plants and can be affected by the environment
how does temperature affect the cuticle thickness
the hotter it is the thicker it is
what is the term for a singular first stomata
stoma
what are trichomes
they are the hairs on the leaf and they can be both unicellular or multicellular
what is the function of the trichomes
they reduce water loss by evaporation by trapping water vapor and increasing humidity by limiting the air movement around the leaf
reflect solar radiation to keep plants cool
some are glandular and release compounds that prevent herbivory
some species have modified trichomes to secrete salt this allows the plant to survive in saline conditions
what is biotic stress
stress to a plant caused by another living organism
what is a weed
any plant that is growing in a place it’s not wanted. this most commonly includes weedy species (plants with no use to humans), volunteer crops, and ornamentals that have escaped
why are weeds a problem in an agriculture system
compete for light, water, and nutrients
contaminate crop
cause quality downgrading
can kill you or your animals
how can weeds contribute to yield loss
due to competing for the essentials of plant growth: water, sun, nutrients
what is a way weed can prevent herbivores from eating them
barbs will prevent this
how do weeds contaminate seeds
when seeds are inseperateable from the crop seed they lower the grade and value of the grain. exwild mustard seed is so similar to canola its impossible to separate by conventional methods
how do weeds contribute to harvest losses
this may occur if the weeds are so thick that harvesting is difficult. making for a slower operation and cost of control
what is earth tag
an example of how weeds contribute to harvest losses. it’s exasperated by green weeds and reduces the quality. (basically, the dirt stick to your seeds)
what is an example of toxic weeds
rhubarb, death camas, and water hemlock
What habits make weeds a problem
because they are hard to control as they are very suited to their environment:
- vigrous growth habits, competitive
- adapt to a wide range of environments
- quick life cycle and produce lots of seeds
- special dispersal mechanism
- effective dormancy mechanisms
what are specialized stems in weeds
these structures are often involved in vegetative reproduction. they allow weeds to be very persistent. they can also be a good food source for humans
what are rhizomes
it a horizontal specialized weed stem that is underground. it serves as an overwintering organ and method of propagation. these stems produce shoots and roots at nodes that grow into a new plant. while establishing itself it gets nutrients from the parent plant
what are some adaptations for weed seed distribution
wind, water, animals
how do weeds get animals to carry seeds
by having barbs that stick to the animal
how do weeds have adaptations for the wind to carry the seed
by having parachutes, wings, or designed for the whole plant to move with the wind
what is an infectious plant disease
another biotic stress is plant doses that is spread from plant to plant and caused by a living agent (pathogen) they are usually extremely infectious and difficult to control
what are the three stages plant disease is broken into
inoculation, incubation, infection
what is the inoculation stage of a plant disease cycle
the period when the pathogen is transferred from a source to a host plant
what is the incubation stage of the plant disease cycle
the time period from when the pathogen reaches the plant until it begins to affect the plant’s function
what is the infection stage of the plant disease cycle
multiplication of the pathogen and the appearance of the characteristics of the disease
for plant disease when are control methods most effective
when implemented during inoculation
what is the best disease management
to prevent or limit disease. if diseases are already present it may be difficult or not economically viable to control
what is the causes for infectious disease
they are caused by microorganisms that attack susceptible plants
what are environmental or agronomic conditions that can favor disease
wet weather
injured or stressed plants
what are some ways plants can be injured or stressed making them more susceptible to disease
herbicide injury, lack of nutrients, hail damage, deep seedling, poor quality seed
what is the most common plant disease-causing organism in western Canada
fungi
why is fungi the most common plant diseasing plant in Canada
because it reproduces by spores. spores can be spread by wind, water, machinery, animals, insects, contaminated seeds, etc.
when moisture is present spores on the plant tissue germanate and grow along the plant surface, and penetrate the plant through the stomata of a plant wound
spores can survive in plant residue in the soil or form overwintering bodies
how do plants react to disease
disease will cause yield and quality loss
what are some symptoms of disease in plants
- death of part or all of the plant
- lesions on stem will cause a loss of photosynthetic area
- changes in coloration
- reduced growth, stunting, dwarfing, wilting
- galls, tumors
what is the best way to identify a plant disease
sometimes you can identify by symptoms but often a lab culture will have to be done
what are the two groups we make for insects when it comes to insect-plant relationships
beneficial and harmful
what are beneficial insects
perform duties advantageous to humans
ex. pollination incests, parasitic insects (wasps lay eggs in aphids and that kills them when they hatch), flies recycle nutrients
what do harmful insects to crops
insects that do damage to crops, food, buildings, etc
how do insects injure plants
they can pass on the disease
direct injure it by directly feeding on the plant tissue
how can insects directly injure plant tissues
- sucking on the plant juices from the leaf
- girdling the stem (damages the vascular tissue)
- chewing on the leaves, flowering parts, developing seed
what are some factors that contribute to how well a plant will recover from insect damage
- insect population
- plant growth stage
- growing condition
- weather
how does insect population affect the damage insects can do on plant
the greater the population size the more and faster the damage will be done
how does the plant growth stage affect the damage insects can do on plants
smaller plants suffer more than large plants. older plants ofter recover better (if they can)
how does the plant growing conditions affect the damage insects can do on plants
good growing conditions lessen the effects on the insect injury. plants are able to attempt recovery if conditions are good for growth
how is weather a factor for if plants can recover after insect damage
some insects function better at different temperatures. some like hot conditions best. often cool or cold temperatures result in insect inactivity
what is the cyclical nature of insects
damage occurs in a cycle related to the life cycle of insects. it may be the larva that does damage or the adult or in some cases both.
some insects have several generations per year others only have one. some insects stay in a stage for many years.
the population is also cyclical as well. the population build-up is a problem and then are reduced by natural parasites or diseases
environmental conditions play a major role in the build-up and decline of insect populations
