Who proposed the cell theory for plants?

$S -$ Assertion: The cell is the structural and functional unit of life.
$R -$ Reason: All living organisms are composed of cells.

The cell theory was proposed in the year $1839$ by Schleiden and Schwann. According to this theory,all organisms are composed of cells,and cells are the basic unit of life. How did this theory contribute to the field of science?

Who observed that plants are composed of different kinds of cells?

With the increase in the size of a cell,its ratio of surface area to volume will be:

Figures of cork cells as seen by Robert Hooke were published in his book: