Question

According to the abc model of floral development, which genes would be expressed in a showy ornamental flower with multiple sepals and petals but no stamens or carpels? Please explain your answer.

Answer 1

Floral development:

Generally flowers are one of the part of the plants.They are usually organized into concentric whorls( sepals, petals, stamens and carpels.)

In reproduction process each of these have a unique role.

• Sepals - Involved in protecting the flower bud.
• Petals - Have beautiful colours to attract the pollinators
• Stamens - It contains male gametes and produce pollen grains.
• Carpels - It contains ovule and produce seed after fertilisation.

ABC model has 3set of homeotic genes A,B,C . By these genes expression organ identity can be determined.

In general 4 main concentric whorls in flowers has been seen ,in which

• whorl  1 - Determined to be sepals - Only Gene A (APETELA1 and APETALA2) involved
• whorl 2 - Determined to be petals - Both Gene A &B (APETELA1 ,APETALA2 ; APETALA3 & PISTILLATA) involved
• whorl 3 - Determined to be stamens- Both gene B& C ( APETALA3 & PISTILLATA ; AGAMOUS) involved
• whorl 4 - Determined to be carpels - only Gene C ( AGAMOUS)

In showy ornamental plants the expression of GENE A & GENE B involved in development of multpile sepals and petals but no stamen or carpels.

Only on co expression of both Gene B and C stamens can be produced ,and complete expression of C produces carpels. Not all the flowers have both stamen and carpels they lack any one of the part, they are called as imperfect flowers.

Hope this helps you to resolve your doubts:)