Gymnosperm pine lifecycle

Flowchart nodes

• Microspore mother cells (2n) inside microsporangium which are inside of microstrobilli 

• Meiosis occurs with each microspore mother cell

• 4 haploid microspores from each microspore mother cell are created

• Each haploid microspore cell divides by mitosis

• 4-celled pollen grain (male gametophyte) are created from each microsporeTwo of the cells are sperm cels and one is a pollen tube

• Megaspore mother cells (2n) inside the megasporangium which is located inside an ovule which is part of a ovuliferous scale which is part of a megastrobilus

• Meiosis occurs with each megaspore mother cell

• 4 haploid megaspores from each megaspore mother cell is created(are not dispersed)

• 1 megaspore lives, 3 dieThe living megaspore undergoes mitosis numerous times

• A 2,000 celled female gametophyte with an archegonium containing an egg cell  is created

• The wind carries the winged pollen to the ovulate of megastrobilli

• The pollen enters the ovule through the micropyle. 

• The pollen grain germinate to form a pollen tube 

• The pollen tube digest its way through the necellus to the archegonia of the female megagametophyte

• The pollen discharges 2 sperm into the egg of an archegonium. One sperm fertilizes with an egg and the other degenerates. A 2n zygote is formed

• The zygote goes through mitosis to create an immature sporophyte which is supplied energy from the female gametophyte.A seed is created with a seed coat, and cotyledons. 

• The scales of the cones separate allowing the seed to be  dispesed by the wind 

• When the environemental conditions are ideal the seed germinates going through the process to create an adult diploid sporophyte

• The process is set up to occur again.