It's been made more than obvious that Obito was capable of using Mokuton, and quite efficiently so as stated Zetsu, when he was young. So why hasn't he been using it ever since he appeared in the series? Especially now against Kakashi's team?
he was in zestu's body and zestu is created from hashirama cells, so Tobi could have use all his abilities why he was inside of the body. but there is some more explanation to come, you just need to wait and you will see