Germination (and flowering)
Breaking Seed Dormancy
Flowering plants (angiosperms) reproduce sexually via cells produced in their flowers. The environmental conditions that stimulate flowering in plants include a period of cold i.e. chill time that informs the plant what time of the year it is. It would be a waste to flower in autumn because the approaching winter would bring conditions not favourable to survival and dispersal of seeds from the flower.
Therefore, a chill period predicts that spring and summer are to follow, so flowering may commence. The process isn’t instantaneous, so the actual flowers finish developing once the climate is optimal rather than in the actual winter.
This response is called vernalisation (FLC stands for flowering locus C – a gene responsible for vernalisation; it is expressed highly in the plant before the chill time, during which it decreases, finally kick starting flowering).
In addition to this, phytochrome (a plant receptor; more on this later) informs the plant on how much daylight is present. It directly responds to light, and controls the processes of growth and flowering.
Right, let’s delve into it!
A bit equivalently to mammalian sexual reproduction, sexual reproduction in plants involves complementary gamete cells that join to create a zygote that further develops into a new organism. of that species.
In plants, pollen grains are equivalent to spermatozoa in mammals, while the embryo sac is equivalent to the ovum. Instead of forming a blastocyst where the embryo starts developing inside a developing placenta, they form a zygote inside a seed that also contains nutrients that the little zygote can use once it starts growing. Yes, we are about to learn about plant reproduction and the events that lead to seeds!
In terms of the formation of pollen grains and embryo sacs, the sequence of meiosis and mitosis between precursor stages of development is similar to that in mammals. Instead of mammalian testes and ovaries…..