Beauty and Sex: Flowering

Flowers are derived from the process of transition from vegetative to generative meristems

Primary and secondary inflorescences

Vegetative and generative meristems

Sepals

PetalsStamens

Carpels

Leaves

SAM

Vegetative meristem Generative meristem

FM

Floral organs are initiated from the floral meristem in concentric whorls

Meristem identity genes → floral organ identity genes → cadastral genes

Floral organ identity genes are responsible for reproductive organ formation

No sepals/petals No petals/stamens No stamens/pistils

Flowering is regulated by internal and external stimuli

Juvenile to adult phase transition is characterized by morphological and physiological characteristics

English Ivy (Hedera helix)

Juvenile to adult transition requires competence (adult vegetative phase), determination and expression

Photoperiodism is an external stimulus of floweringShort-day, long-day and day-neutral plants

Night break inhibits flowering Night break of sufficient duration induces flowering

Photoperiodism is an external stimulus of flowering

Plants are adapted to day-length at different latitudesPhytochromes and cryptochromes are the photoreceptors that regulate flowering

West Lafayette

Natural variation in Arabidopsis

Germany West-Africa

Plants are adapted to day-length at different latitudesPhytochromes and cryptochromes are the photoreceptors that regulate flowering

Ler

Cvi

Ler

Cvi

Plants track time with their circadian clock

Periodic rhythm of plant processes that is regulated by an internal timepiece

CO (CONSTANS) and FT (FLOWERING LOCUS T ) are regulators of flowering in Arabidopsis (long-day plants)

CO expression is clock controlledCO protein accumulation is regulated by proteolysis

Similar homologs Regulate flowering in short-day plants

Rice (short-day plant) - Heading-date1 (Hd1) = CO and Heading-date3 (Hd3) = FTHowever, Hd1 inhibits Hd3 activation of flowering

Vernalization is required before some plants are responsive to photoperiodic-induced floral transition

FLC negatively regulates flowering

Vernalization is required before some plants are responsive to photoperiodic-induced floral transition

FLC negatively regulates flowering

Plant Biology (2010) Smith et al.

Florigen is the biochemical signal for flowering

Zeevart (2007) Taiz and Zeiger Web Essay 25.2

FLOWERING LOCUS T

Plant Biology (2010) Smith et al.

Integration of flowering stimuli