The northern hemisphere is warmer in the summer than the winter because the northern hemisphere are pointing toward the sun. Because of this the rays hit us more directly making is hotter. So during the winter when the northern hemisphere is not pointing toward us, it makes is colder. It also depends on the tilt of the axis. When it is more direct it makes the temperature hotter.
Illumination results auxin moving to the dark side of stem tips. As this auxin diffuses down the dark side ofthe stem, the cells respond by enlarging. This causes the plant to bend toward the light.
