cleistogamous flowers , mostly do not have petals then how do they cover their male and female cones ?

Dear student.

Cleistogamous flowers are those that do not open at all, so they do not need to cover the male and female cone separately. They prefer self-pollination.  After self-pollination a cleistogamous flower may open, but some cleistogamous flower never open and remain closed throughout their life.

Regards.