All hormones Flashcards
what is the chemical nature of auxin
IAA is the naturally occuring form of auxin
- synthesized from tryptophan
Where is auxin synthesized
leaf primorida
young leaves
developing seeds
How is auxin transported
cell to cell
unidirectional (polar) transport
What are the effects of auxin
- apical dominance
- tropic responses (phototropism)
- vascular tissue differentiation
- promotion of cambial activity
- induction of adventitious roots from cuttings
- inhibition of leaf and fruit abscission
- stimulation of ethylene synthesis
- inhibition of promotion of flowering
- stimulation of fruit development
What is the chemical nature of cytokinin
N^6 adenine derivative
phenyl urea compounds
Zeatin is the most common cytokinin in plants
Where is cytokinin synthesized
In root tips
How is cytokinin transported
are transported via the xylem from roots to shoots
What are the effects of cytokinin
- cell division
- promotion of shoot formation in tissue culture
- delay of leaf senescence
- application of cytokinin can cause release of lateral buds from apical dominance
What is the chemical nature of ethylene
- gas
- C2H4
- synthesized from methionine
- the only hydrocarbon with a pronounced effect on plants
where is ethylene synthesized
in most tissues in response to stress, especially in tissues undergoing senescence or ripening
How is ethylene transported
being a gas it moves by diffusion from its site of synthesis
What are the effects of ethylene
- fruit ripening (especially in climacteric fruits: apples, bananas, avocados)
- leaf and flower senescence
- leaf and fruit abscission
what is the chemical nature of ABA (abscisic acid)
synthesized from mevalonic acid
- no effect of abscission
Where is ABA synthesized
in mature leaves, especially in response to water stress.
May be synthesized in seeds
how is ABA transported
exported from leaves in the phloem
What are the effects of ABA
- stomatal closure
- induction of photosynthate transport leaves to developing seeds
- induction of storage protein synthesis in seeds
- embryogenesis
- may affect induction and maintenance of dormancy in seeds and buds of certain species
What is the chemical nature of Gibberellin
GA3 (gibberellic acid) a fungal product is most widely available.
GA1 is probably the most important gibberellin in plants.
GAs are synthesized from mevalonic acid
Where is Gibberellin made
in young tissues of the shoots and developing seeds
uncertain whether synthesis also occurs in roots
How is GA transported
GAs are transported in the xylem and phloem
What are the effects of GA
- hyperelongation of shoots by stimulating both cell division and cell elongation
- producing tall plants
- induction of seed germination
- stimulation of flowering in long day plants and biennials
- regulation of production of seed enzymes in cereals
What is the chemical nature of Brassinolides
steroids
What are the effects of brassinolides
- stimulate cell division and elongation
- Arabidopsis mutations that block synthesis of brassinolides produce dwarf plants
What is the chemical nature of salicylic acid
phenolic compound
what is the effect of salicylic acid
activate pathogen defense genes
