Describe some of the problems encountered by the evolution of aquatic plants to land?

Answer 1

1. Water loss
2. Gas exchange in a non-aquatic environment
3. transfer of pollen/spores that does not rely on water
4. loss of support by water
5. transport of water from roots to leaves

This sounds like homework, so you can look up the ways plants have dealt with these issues at the link

Answer 2

Also to add to the above aquatic plants are usually limited by phosphates, while terrestrial plants are limited more often by nitrate/nitrite availability.