I like the diagonal composition, where the leaves lead you to the flower. The narrow DOF pushes the green leaves out of focus very nicely. The black background isolates the subject nicely. On the negative side the higlights on the edges of the flower are very bright and are a bit ditracting. Also the narrow DOF is hurting you here as some of the petal edges seem out of focus.
The viewpoint is a little common and may not standout within a competetive Free Study environment. I like macro (and am jealous of your lens -- and I have a A350 to boot). You could try differnt angles and aperature sizes and see what provides more of a wow factor to excite the viewers. Not always easy to do :)