Somatic Mutations in meristem tissue in plants
You can see the wikipedia article on meristem.

The apical meristem differentiates into floral meristem that gives rise to flowers.
From this the cells specifically expressing APETALA3 (AP3), PISTILLATA (PI), AGAMOUS (AG) and SEPALLATA (SEP) would give rise to the stamen [ref]. 

CRC gene is essential for female development and plants lacking this will not produce pistils. So cells expressing this gene will give rise to female parts[ref].

Nonetheless mutation happening at any stage of the development of floral meristem can be transmitted to the pollens/ovules if the mutated cells stochastically give rise to that lineage.