Which part of the flower performs a similiar role to the testes in the male reproductive system?

The part of a flower that imitates the human male reproductive system is called the stamen, and the part that imitates the testes are the microspores on the anther.
The stamen has two main parts. First, the stamen has a long, slim stalk called the filament. Second, at the end of the filament is the anther. The anther is full of little yellow pollen sacs called microsporangia, which would be similar to the human male testes. These microspores germinate into a male gametophyte, which produces sperm.
Conversely, the female organs are called the pistil (or carpel), which has three main parts: the stigma (sticky part where pollen from the male parts land), the style (narrow stalk), and ovary (innermost part that contains ovules).
Fertilization occurs when pollen lands on the stigma and grows down into the ovary, where a zygote can grow.
For more botany definitions, see the UC Berkeley glossary (below).
http://www2.estrellamountain.edu/faculty/farabee/biobk/BioBookflowers.html

https://ucmp.berkeley.edu/glossary/gloss8botany.html