Symplastic movement is slower than apoplastic movement because

The correct option is "molecule has to enter through cell membrane".

To understand why symplastic movement is slower than apoplastic movement, we need to compare the pathways that water and solutes take through plant tissues:

1. Apoplastic Pathway:
In the apoplast pathway, water and minerals move exclusively through the non-living parts of the plant, which includes the cell walls and the intercellular spaces. Because this movement does not involve crossing any selectively permeable cell membranes or entering the cytoplasm, there is very little resistance, allowing the movement to occur rapidly by bulk flow.

2. Symplastic Pathway:
In the symplast pathway, water and solutes travel through the living parts of the cells. The molecules must first cross the selectively permeable cell membrane (plasma membrane) to enter the cytoplasm of a cell. Once inside, they move from cell to cell through microscopic cytoplasmic channels called plasmodesmata. Crossing the cell membrane is a highly regulated process that encounters significant resistance compared to moving through cell walls, making symplastic transport much slower.

Therefore, the necessity for molecules to enter through the cell membrane is the primary reason why symplastic movement is slower than apoplastic movement.