Athin, flexible, semipermeable barrier around the cell which regulates what enters and leaves the cell.
example: gatekeeper for the cell.

Ali hypothesized that increasing fertilizer would increase plant growth. four groups of thirty similar plants were given 0 to 15 ml of fertilizer, as shown in the graph. the change in plant height for each group over a two-week period was averaged and recorded. plant group fertilizer added (ml) avg. growth (cm) a 0 4 b 5 6 c 10 8 d 15 3 what is the best conclusion based on this data? the hypothesis was not supported because the data indicated that fertilizing plants does not improve plant growth. the hypothesis was supported; to get the best growth, use 5 milliliters of fertilizer per plant. the hypothesis was not supported; the data indicated that too much fertilizer can inhibit plant growth. the hypothesis was supported; to get the best growth, use 15 milliliters of fertilizer per plant.