What adaptation do seed plants have in addition to the seed that is not found in seedless plants?

gametophytes

vascular tissue

pollen

chlorophyll

The correct answer will be option-pollen.

Explanation:

The pollen are the male gametophyte which is produced in the seed plants.

The pollen produce male gametes after entering the female gametophyte. The male gametes fuse with the egg cell and form the embryo inside ovary which matures and forms seeds. The vascular seed plants lack these pollen but instead produces male gametes in gametangia which are replaced by the pollen in the seed plants.

Thus, option-pollen is the correct answer.