Question

what would have happened if a plant cells did not have a cell wall

Answer 1

HEY ANSWER IS...................!!

the cell wall supports and protects the plant cell 

take osmosis for example, 
only plants are exposed to fresh water, animal cells and bacteria are rarely , usually never, exposed to fresh water. since the solution or cytoplasm inside the cell membrane is hypotonic (less concentrated with water) than the fresh water , osmotic pressure will cause water to diffuse across the cell membrane into the cell (osmosis), trying to equalize the concentration, causing the cell to inflate. the cell wall protects this cell from bursting. so if there was no cell wall, plants could not intake fresh water. 

I HOPE THIS ANSWER HELPS YOU MORE.......................!!

Answer 2

Hii..

Cell wall is a tough rigid sturucture present only in plant cell for a barrier against microbes and outer environment.

If the plant cell didnt have a cell wall then they would not be protected against any microbes or the nutrient uptake would not be easy .
Eventually the plant would die.

In absence of cell wall if the outer climatic conditions are changed the protoplasm would be direct in contact of air and it would eventually get affected.

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Hope this helps!