This is the 15002nd most frequent Russian word.
подсолнечника
"Подсолнечника" means "sunflower" in English.
Here, 'подсолнечника' is used as a noun in genitive singular form showing possession or relation.
В поле растёт красивое поле подсолнечника.
There is a beautiful sunflower field growing in the meadow.
Here, 'подсолнечника' is used to describe the origin of the seeds, again in genitive singular form to denote origin.
Я люблю вкус семечек подсолнечника.
I love the taste of sunflower seeds.
Here, 'подсолнечника' is in the genitive singular to identify the type of flower.