The table summarises a student’s observations of three cell types, P, Q and R, taken from a transverse section through a plant stem and viewed using a light microscope. P: ratio of cell wall width to whole cell width = $1:10$, structures seen in cell contents = none Q: ratio of cell wall width to whole cell width = $1:20$, structures seen in cell contents = regular pattern of circles in some cells R: ratio of cell wall width to whole cell width = $1:20$, structures seen in cell contents = granular appearance of all cells What kind of cells are P, Q and R?
- AP: companion cell, Q: phloem sieve tube element, R: xylem vessel element
- BP: companion cell, Q: xylem vessel element, R: phloem sieve tube element
- CP: xylem vessel element, Q: companion cell, R: phloem sieve tube element
- DP: xylem vessel element, Q: phloem sieve tube element, R: companion cell