9.3 Reproduction in Angiospermophytes Flashcards Preview

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Flashcards in 9.3 Reproduction in Angiospermophytes Deck (7)
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Define pollination

The transfer of pollen grains from the mature anther to the receptive stigma (usually of another plant) often facilitated by animals, wind or water movement


Define fertilisation

Fusion of the male gamete in the pollen grain with the female gamete in the ovule to form a zygote


Outline seed dispersal

Fertilised ovules form seeds which move away from the parental plant before germination, reducing competition for resources. Seed dispersal mechanisms include fruit, wind, water and animals


Define germination

The process by which a seed emerges from a period of dormancy and starts to sprout


Outline three factors which a seed requires for germination

• Temperature for the optimal function of enzymes
• Oxygen for aerobic respiration (seed needs ATP to grow)
• Water to metabolically activate the cells



Outline the metabolic processes during germination of a starchy seed

• Water is absorbed, which causes the formation of gibberellin in the embryo's cotyledon
• Gibberellin stimulates the production of amylase, which catalyses the breakdown of starch to maltose
• Maltose is transported to the embryo, where it is either hydrolysed to glucose (for energy) or polymerised to cellulose (for cell wall formation)


Explain how flowering is controlled in long day and short day plants

• Flowing is affected by light
• Phytochrome exists in two forms, Pr which absorbs red light and Pfr which absorbs far-red light
• Pfr is active form, Pr is inactive form
• Daylight converts Pr to Pfr
• In darkness, Pfr gradually reverts back to Pr
• Pfr acts as promoter of flowering in long-day plants
• In long day plants, flowing induced by dark periods shorter than a critical length because enough Pfr remains at the end of short nights to stimulate flowering
• Pfr acts as inhibitor of flowering in short-day plants
• Short-day plants induced to flower by dark periods longer than a critical length because at end of long nights enough Pfr has been converted to Pr to allow flowering to occur