9.4 Flashcards
Draw half views of animal-pollinated flower
XX
Explain how Pfr controls flowering in long day plants
in long day plants, Pfr stimulates flowering
in midsummer long days allow conversion of lots of Pr into Pfr
the short nights mean not much of Pfr is converted back into Pr
Which means high levels of Pfr accumulate and since Pfr stimulates flowering, they flower during summer
Explain how Pfr controls flowering in short day plants
Pfr inhibits flowering in short day plants
When days are short, nights are long allowing enough time for much of the Pfr to be slowly converted back to Pr
Pfr levels drop below a threshold which removes the inhibition of flowering
NB: dark period must be uninterrupted, even a flash of light could cause Pfr to be rapidly produced
What are the methods to induce short day plants to flower out of season
By artificially extending the length of the uninterrupted dark period so it’s longer than critical length for flowering
By shining a flash of FAR RED light on the plants, causing rapid production of Pfr back to Pr
Briefly describe the difference between pollination, fertilisation and seed dispersal
pollination: the transfer of pollen from anther to stigma
fertilisation: the fusion of male and female gametes to form a zygote
seed dispersal: the carrying of seeds away from parent plants
Explain how most flowering plants use mutualistic relationships with pollinators in sexual reproduction
mutualism= an association b/w 2 organisms where both benefit
pollinators benefit from food (nectar, pollen)
plants gain a means to transfer their pollen from anthers to stigmas of other plants
Draw the structure of a seed
XX
What is germination
the development of a seed into a functional plant
What are the conditions required to overcome dormancy
WATER- to rehydrate seed and cause the tests to split
OXYGEN- needed for aerobic respiration to produce ATP
SUITABLE TEMPERATURE- close to optimum temperature for enzymes involved in metabolism and growth
Outline the metabolic processes during germination of a starchy seed
germination begins with the uptake of water by the seed which rehydrates the tissues and causes the tests to split
water uptake triggers release of GIBBERELLIC ACID by the embryo
GA passes to the food storage cells where it stimulate production of AMYLASE
amylase causes hydrolysis of stored starch to maltose
maltose is further hydrolysed to glucose which is either used in respiration or converted into molecules for growth
