9.3.1 Draw and label a diagram showing the structure of a dicotyledonous animal pollinated flower. Know: Sepal Petal Anther Filament Stigma Style Ovary
9.3.2 Distinguish between pollination, fertilization, and seed dispersal. Pollination – Transfer of pollen from anther to stigma by wind, insect etc. Fertilization – the sperm entering the egg Seed Dispersal – Seed = plant embryo + food reserves +testa – Seed being moved from mother plant via explosion, wind, consumption, or animal Germination the seed absorbing water and beginning to grow and develop
What is pollination? Transfer of pollen from one anther of one flower to the stigma of another. Can happen on the same flower: self-pollination
9.3.3 Dicot seed structure The IB calls the seed coat a “testa”
Seed dispersal Seeds are dispersed in various manners: – Wind – Water – Animals The structure of seeds indicates their dispersal type
9.3.4 Germination of Seeds Conditions required: – Moisture Needed so that metabolic action can take place – Temperature – Oxygen – A period of dormancy – Some conditions differ depending on seed and its environment
9.3.4 Explain the conditions needed for the germination of a typical seed. Conditions vary among species Depth of soil Consumption by animals -- Seed is excreted in fertilizer Water****** most important – Most species require an increase in moisture Temperature – Some species require intense heat (fire) – Some species require a cold season followed by warmth Germination often follows Fire, drought or flood
9.3.5 Outline the metabolic processes during germination of a starchy seed. Water enters through the micropyle Gibberellin (a plant hormone) is produced in the cotyledon Gibberellin stimulates the production of the amylase. Amylase catalyses the breakdown of starch into maltose Maltose diffuses to the embryo for energy release and growth.
Germination of a dicot seed Water is absorbed by the seed, kickstarting the formation of the hormone gibberellin Water enters Gibberellin forms here
Germination of a dicot seed Gibberellin stimulates production of the enzyme amylase, which digests the starch in the seed into maltose Gibberellin Amylase Stimulates production of
9.3.6 Explain how flowering is controlled in long and short day plants, including the role of phytochrome. The seasonal change in the length of the period of daylight or the period of darkness can control flowering. Long-day plants flower in the summer,when nights have become short enough. Short –day plants flower in the autumn, when the nights have become long enough.
9.3.6 Explain how flowering is controlled in long and short day plants, including the role of phytochrome. Phytochrome—a plant pigment that receives red light, used to measure day length by plants. When phytochrome receives red light after a dark period (night), it can signal that night is over. If the dark period was short enough, this causes a long day plant to flower. When phytochrome receives a red light during a dark period (night) it can signal that night is over. This inhibits a short day plant from flowering, because the night was not long enough.
A flash of red light signals the end of the dark period. A flash of far-red light cancels the effect of the red flash. 2 forms of Phytochrome P R --Phytochrome that receives red light P FR --Phytochrome that receives far red light When P R receives red light, it switches to P FR. When P FR receives far red light, it switches to P R. In darkness, P FR converts to P R –because it is the more stable form.
Phytochrome Long-day plants flower in the summer, when nights have become short enough. Because the night is so short, enough P FR remains to signal the transcription of genes controlling flowering when the dawn breaks, and P FR receives the dawn’s far red light. – Long-day plants have a master gene that initiates flowering when switched on by P FR Short-day plants flower in the autumn, when the nights have become long enough. P FR inhibits flowering, but breaks down before the long night is over. The dawn’s early light is received by the plant, and with no P FR, the plant begins the flowering process. – Short-day plants have a master flowering gene that is switched off by P FR