Plant Responses to the Environment - Hormones Flashcards
what to the physiological effects of hormones depend on (5)
- hormone concentration
- tissue type
- tissue age
- presence of other hormones
- environment
mixing of hormones results in… (2)
- wide range of effects
- can differentiate concentrations and tissue location
what physiological processes are regulated by gibberellins (3)
- seed germination
- cell elongations (with auxins)
- flowering
seeds
- structures that protect the embryo and serve as energy source for the seedling upon germination
components of seed (4)
- aleurone
- endosperm
- embryo
- seed coat
seed aleurone
- source of amylase enzyme used to break down starch into sugars
seed endosperm
- surrounds the embryo and store energy in the form of starch and other nutrients
seed embryo (2)
- the multicellular organism before it emerges from the seed
- source of gibberellins
seed coat
- semi-hard covering that creates a barrier between environmental factors and the embryo
what are the requirements of seed germination (5)
- rehydration
- oxygen
- suitable temperature
- remobilization of energy reserves
- facilitated by red light (Pfr)
how does Pfr affect germination
- increases the amount of GAs
how does Pr affect germination
- decreases the amount of GAs
what does abscisic acid regulate
- multiple plant responses to stress, including seed dormancy and stomatal closure
when does ABA interfere with the germination pathway by GA (3)
- ABA inhibits synthesis of amylase in the aleurone layer
- no nutrients are available for germination
- germination is delayed
how does ABA control stomatal closure (2)
- ABA synthesized in the roots in response to stress (dehydration) will travel using xylem and promote stomatal closing
- the roots are the first to detect lack of water
how does ABA affect the solute potential of stomatal guard cells
- makes it less negative
senescence (3)
- involves degradative biochemical processes and leads to death
- can be triggered by the environment or as a natural response to aging
- associated with low accumulation of CKs in leaf tissue
seasonal senescence (2)
- plant decides when leaves are not worth it to be maintained
- leaves senesce to make better use of the nutrients
sequential senescence (2)
- older leaves that are not as efficient are killed
- nutrients are used for younger tissue
what will result from treatment of senescing leaves with cytokinins (2)
- delayed senescence
- leaves stayed greener for longer
ripening (2)
- transition of fruits from physiological maturity to senescence
- facilitates reproduction by facilitating seed dispersal and preparing the seed-bearing organ for detachment from the plant
stages of ripening (3)
- cell division until the right amount of cells is achieved
- cell expansion until the right size is achieved
- ripening
climacteric fruit (2)
- ethylene-dependent fruits; require ethylene for production
- can ripen after harvesting
non-climacteric fruits (2)
- ethylene-independent fruits; require ABA, and not ethylene, for production
- only ripens in the plant
ethylene (4)
- simplest structure of all plant hormones
- gaseous, non-polar, hydrophobic molecule that freely diffuses across the plasma membrane
- production is autocatalytic
- activates multiple aging-related processing
how is ethylene autocatalytic (2)
- production is linked with a respiratory burst
- once the hormone levels reach a threshold level, it is able to activate its own synthesis; presence of ethylene activates synthesis of more ethylene
what age-related processes does ethylene activate (3)
- ripening, senescence, abscission
abscission
- separation of the organs from the plant
to avoid premature ripening, what conditions would you store fruit
- to avoid respiratory bursts: high CO2/low O2 concentrations
what will result from placing two ripening fruits next to each other
- acceleration of ripening of both fruits
ethylene promotes fruit ripening by enhancing the expression of: (4)
- chlorophyll degradation enzymes
- fruit softening enzymes
- fruit sweetening enzymes
- senescence associated genes
