I believe that B. dolichomerithalla is cold hardy to about 25F. Where the leaves touched the plastic, you will get leaf burn.

I recommend(next time) covering the plant with a thick blanket, such as a comforter, to get a barrier between the plastic and the plant.

Some leaf burn is expected though, even without covering. After the bamboo has been in the ground for a couple of years, it will get more acclimated and be more cold hardy.

Most of my bamboo is too large to cover, so I am always sure to WATER WELL before a freeze, which helps with freezer burn. Planting the less cold hardy ones behind a windbreak or next to a warm building also helps.

Yours should be fine, and will come back nicely in the Spring.

Good Luck

Kt