1.)
The process of collecting solar energy and using it to produce food or glucose, which is like energy for the plant cells, is called photosynthesis.
It is the Chloroplasts' job to carry the photosynthesis process out.
2.)
The surface area to volume ratio gets smaller as cells grow. So, if the cell grows past a certain size, not enough material can cross the membrane fast enough to make room for the larger cellular volume.
I hope this helps!