Mealwood plants no longer produce a seed at the end of their life cycle. Not sure if this is true for other plants, yet. So now you get the 5 harvests from a mealwood plant then you can't replant it.
Steps to Reproduce
Plant a Mealwood plant. Harvest it through its 5 cycles. No seed produced.
This issue has been closed either because it is not a bug or does not belong in the bug tracker.