It was Sunday yesterday. The weather was fine. It was sunny and there were no clouds in the sky. Sandy and Sue got up early in the morning. Now they were in the park. It is a big park and it's so beautiful. They saw many people there. Some boys played football on the grass. Some girls danced under the tree. An old man walked beside the lake. A young woman and her little son looked at the fish in the lake. How happy they are!

如图，已知抛物线y=ax²+bx+c的顶点D的坐标为（1，$-\frac{9}{2}$），且与x轴交于A、B两点，与y轴交于C点，A点的坐标为（4，0）．P点是抛物线上的一个动点，且横坐标为m．

不能正常发育，杂合子植株完全正常．现有基因型为Dd的苦瓜植株若干做亲本，下列有关叙述错误的是（　　）