Demeter just couldn't accept this. She threatened to leave her duties of taking care of Earth behind and let the world die. Zeus had to come to a compromise.
At the gathering, Zeus questioned Persephone on where she wanted to live. She claimed that she wished to live in the underworld with her husband. Demeter was confused and enraged. She was convinced that Hades had done somethong to her daughter.
Zeus had to make sure everyine was happy, meaning Persephone, Demeter, and Hades. So, he settled on having Persephone live with her husband in the underworld with Hades for 6 months, and then live in Olympus with Demeter. This gratified everyone.
The reason why we have seasons all connects to this. Those 6 months where Demeter and Persephone are seperated , Demeter is not in the mood to care for the plants, so she tends to neglect them. This is Winter and Fall. When Persephone returns, Demeter is overjoyed and the plants reflect her personality. This is Spring and Summer. So, as you can see, this is why we have seasons.
Demeter was in a state of consternation. She was so upset that she began to sotp taking care of the plants and they slowly began to wilt and die (Autumn). She looked everywhere and decided on going to Helios, the sun God, who witnesses everything. She laid prostate and beseeched to him. His sympathy for Demeter led him to tell her that Persephone was kidnapped by Hades.
Persephone had not stop crying from despair once she entered the underworld. Hades, then offered her a few pomegranate seeds. Little did she know that whoever ate these seeds would crave the underworld and wish to live there.