Warm up

List the steps for germination of starchy seed.

The processes of germination begins with the absorption water. This causes the production of gibberellin acid, GA for short. The GA then causes the synthesis of amylases which is used to break down starch and make it into maltose. This maltose is then transported to the embryo and used for two different purposes. It could either be made into glucose (energy for the embryo) or polymerized to cellulose (for cell wall formation). The absorption of water will also form enzymes, triglycerides and phospholipids out of the stored proteins and lipids. Germination uses the food stored in cotyledons as an energy source until the developing shoot reaches the light and can begin to make its own food through photosynthesis.

 

Explain how flowering is controlled in long day and short day plants, including the role of phytochrome

Phytochrome  is affected by light and controls flowering.  Phytochrome exists in two forms Pf and Pfr. The P_fr form is the active form of phytochrome, while the P_r form is the inactive form of phytochrome. Sunlight is composed of more red light then far red, so the P_fr form is mostly active during the day, with the P_r form is mostly active at night.
 In long day plants, the active P_fr form is a promoter of flowering and so flowering is induced when the night period is less than a critical length and P_fr levels are high. In short day plants, the active P_fr form is an inhibitor of flowering and so flowering is induced when the night period is greater than a critical length and P_fr levels are low.