The picture is a schematic diagram of the anatomical structure of a pea flower and its pistil. Please answer the following questions (1) Please fill in the structure name of the stamen on the horizontal line: ①______②_

(1) Please fill in the structure name of stamens on the horizontal line: ①Egg cell ②Pollen grain ③Pollen tube ④Integument ⑤Ovary wall

(2) Pea is a natural plant in nature A relatively strict self-pollinating plant. After fertilization, if 7 seeds are produced in the fruit, it means that the pistil has at least 7 ovules.

(3) Double fertilization is a fertilization phenomenon unique to angiosperms. The double fertilization process: on the one hand, the fusion of sperm cells and egg cells forms a diploid zygote, restoring the original characteristics of various plants. The number of chromosomes maintains the relative stability of species genetics; on the other hand, another sperm cell fuses with 2 polar nuclei or 1 secondary nucleus (central cell) to form a triploid primary endosperm nucleus and its development into of endosperm.

So the answer is: (1): ①Egg cell ②Pollen grain ③Pollen tube ④Integument ⑤Ovary wall

(2) Autoflower; ovule;

< p>(3) Double fertilization is a fertilization phenomenon unique to angiosperms. The double fertilization process: on the one hand, the fusion of sperm cells and egg cells forms a diploid zygote, restoring the original chromosome number of various plants and maintaining Relative stability of species genetics; On the other hand, another sperm cell fuses with 2 polar nuclei or 1 secondary nucleus (central cell) to form a triploid primary endosperm nucleus and the endosperm it develops into.