What are vegetative structures?
young plant (after germination) that grows roots, stems and leaves. it is in its vegetative phase
When does a change from vegetative phase to reproductive occur?
when meristem in shoot start producing parts of flowers instead of leaves
What does the structure of flowers allow?
Why are flowers a reproductive shoot?
they are produced by shoot apical meristem and allow sexual reproduction
What can trigger the transformation of leaf producing shoot to flower producing shoot?
temperature and dark period length
What is a short day plant?
flower when the dark period becomes longer than a critical length (eg. autumn)
Example of short-day plant
What is a long-day plant?
they flower during the long days of early summer when nights are short
Example of long-day plant
How is flowering controlled?
amount of light needed for the production of inhibitors or activators of genes that control flowering
Outline how flowering involves a change in gene expression in shoot apex in long-day plants
active form of pigment PHYTOCHROME leads to transcription of a flowering time (FT Gene); FT mRNA is transported; in phloem to the shoot apical meristem; FT mRNA is translated into FT protein; FT protein binds to a transcription factor; activates many flowering genes; transforms leave-producing apical meristem into reproductive meristem
Which pigment in leaves measures the length of dark periods?
what are the two forms for phytochrome?
P(R) and P(FR)
What happens when P(R) absorbs red light?
converts to P(FR)
What happens when P(FR) absorbs far-red light?
converts to P(R). this is not as important as sunlight contains more 630 nm wavelengths (red light)
Is P(R) or P(FR) more stable?
P(R) more stable, so in darkness P(FR) naturally gradually converts to P(R)
What is the active form of phytochrome?
To which form of phytochrome do receptor proteins bind to?
receptor proteins in cytoplasm bind to P(FR)
How does phytochrome stimulate flowering in long-day plants?
P(FR) acts as promoter for flowering in lond-day plants; large amounts of P(FR) remains at the end of short nights to bind to receptors which promotes transcriptions of genes needed for flowering
How does phytochrome stimulate flowering in short-day plants?
P(FR) inhibits the transcription of the genes needed for flowering in short-day plants; but during long nights most is converted to P(R); inhabitation fails and plant flowers
Explain how flowering is controlled in long-day and short-day plants
flowering is affected by light; pigment called phytochrome; exists in two forms P(R) and P(FR); P(R) absorbs red light and converts to P(FR); sunlight contains more red light so P(FR) predominates during day; P(R) is more stable than P(FR); in dark periods P(FR) gradually converts to P(R) P(FR) is active form; Long-day plants flowering induced by dark periods which are shorter than critical length; large amounts of P(FR) remains at the end of night; P(FR) acts as a promoter for flowering in long-day plants; flowering is stimulated; short-day plants flowering induced by dark periods which are longer than critical length; P(FR) inhibits flowering in short-day plants; enough darkness to convert P(FR) into P(R) to allow flowering to occur
What method is used to induce short-day plants to flower out of season?
additional light in the middle of the night leads to flowering in the off-season provided that enough humidity and nutrients are provided for long long-day plants
Why is flower forcing used?
to get flowers to bloom out of season at a specific time where growers manipulated the length of day and night to force flowering
Draw diagram of an animal pollinated flower
- testa/seed coat
What is function of the petals?
help insects find flower/landing space.
What is the function of sepals?
protect flower bud during its development and at night when buds close
What is the function of anthers?
produce pollen, containing male gametes
What is the function of filaments?
hold anthers in position where thy are likely to brush pollen onto visiting insects
What is carpel?
female art of flower; consists of stigma, style and ovary
What is the stigma?
sticky and captures pollen from visiting insect