Crocus and Tulip flower shows response to

The opening of several flowers that bloom in spring depends mainly on temperature. A small temperature rise in the morning is adequate for full opening of Ficaria, Galanthus, Tulip and Crocus. 
In most species, flower closure responds to external factors in a way similar to opening. In some species, however, closure is apparently due to an endogenous rhythm even if opening is not. In still other species, closure is due to senescence.
Tulip and Crocus are examples of flowers that close due to a temperature drop. The minimum decrease in temperature was about equal to the temperature rise required for opening.