How does the male reproductive cells reach the female reproductive cells in flowers of such plants (pea plants)?

Explanation

(1) In self pollinated plants are usually present above the stigma.
(2) Pollen from the anthers drop on the stigma a process that takes place as the flowers close for the night and that something occurs before they are completely developed and ready to open.
(3) At the time of pollination slightest movement of the flower's petals to simulate the stamen to dislodge its pollen and transfer it to the near by stigma is pea plant.
(4) Pollination usually occurs before the flower is fully open.