There are so many things I love about your photo. The colors are wonderful, the contrast is great, the detail is nice too.
There are just so many lines that the eye has no where to go. When I look at this picture my eyes stare at the many beautiful veins that the leaf has. My eye is not actually being lead from a point A to a point b. Now at the top of the photo the tip of the leaf draws you to the upper left hand corner. This is nice, but not enough of a leading line.
I think that this photo is very good actually and I looked at your profile and you are so talented and have a very good eye. This just wasn't the best choice for this challenge. The idea that sbeaumont had is a great one.
If there was a bug or something at the tip of the leaf the lines would have more of a role in leading the eye. As it is, I think they are just lines and not "leading" lines. It is a very competent macro however with great lighting and detail.