Dehydration vs sunburn

From BonsaiWIKI

It's important to be able to recognize the potential symptoms of underwatering that can lead to dehydration, and overexposure that might result in sunburn.

Sunburn affects the broad faces of the leaves first, not the leaf margins. It is caused by a excessive temperature within the leaf. Here's a picture that shows the result of sunburn:

Dehydration affects the leaf margins first. It can occur as a result of overwatering or excessive wind.