What is the turning point of the story The Nightingale and the Rose?

The turning point of the story The Nightingale
and the Rose is when the professor's daughter rejects the student's red rose
and, in turn, the student throws the red rose away in the gutter, with a passing cart
running over it.

The Nightingale's ultimate sacrifice was
to color a white rose into red by using his own blood, sacrificing his life in the name
of the love that the student feels for the professor's vain daughter. That part of the
story could be deemed as the climax, because the ultimate action was finally achieved
after the nightingale asked nearly everywhere for a red rose, without being able to find
it.

Yet, we all expect this great sacrifice to be equally
rewarded by the undying love of the main couple. Yet, in a dramatic twist, the exact
opposite happens: The girl finds the red rose almost insulting, since she was preferred
jewels and gifts. Moreover, the boy, far from suffering her ungratefulness, proves to be
ungrateful himself by tossing the flower aside and declaring that logic is greater than
love.

Hence, the nightingale not only sacrificed his life
in vain, but also love, as an ideal, becomes a byproduct of immaturity and not the
greatest and most powerful force that the nightingale thought it to
be.