Which plant organ transports substances up and down the plant?

The plant organ that transports substances up and down the plant is the stem. The stem has two types of vascular tissue, xylem and phloem.

1. Xylem: This tissue transports water and minerals from the roots to the rest of the plant. The movement is unidirectional, i.e., upwards.

2. Phloem: This tissue transports the food prepared by the leaves to all parts of the plant. Unlike xylem, the movement in phloem is bidirectional, i.e., it can move both up and down the plant.

So, in summary, the stem, with its xylem and phloem tissues, is the plant organ responsible for the transportation of substances up and down the plant.