Florigen – Definition, Meaning, Stages, Importance, Facts

What Are Florigen?

Florigen is a plant hormone or flowering signalling molecule. Mikhail Chailakhyan, as far back as the 1930s, hypothesized that there must be something produced in the leaves, which is mobile and moves to the shoot apical meristem, inducing flowering in plants.

Only recently, this concept has been confirmed by experimental works on grafting and identification of genes like FT of Arabidopsis. It thus plays a critical role in the biology of plants: florigen mediates the vegetative growth-to-reproductive development transition and, in doing so, ensures flowering takes place in response to environmental signals for photoperiod and temperature to achieve optimum reproductive success.

Structure and Function of Florigen

The structure of florigen is discussed below-

Molecular Structure Of Florigen

Under the name FT protein, florigen is known to be a small polypeptide and mobile signalling molecule in the induction of flowering.

Synthesis And Regulation Of Florigen In Plants

Florigen synthesis occurs in leaves under certain photoperiod conditions. The control of florigen biosynthesis is exerted by genes encoding a mobile flowering signal, FLOWERING LOCUS T.

Role Of Florigen In The Flowering Process

Induction of flowering in plants

This florigen moves from leaves into the shoot apical meristem, inducing the switch from vegetative development to reproductive development.

Transport and signalling pathways of florigen

Florigen moves complexing with proteins like FD through phloem, and through it, flowering genes are turned on.

Mechanisms Of Florigen Action

The mechanism is discussed below-

Genetic And Molecular Basis Of Florigen Function

The FT gene and its paralogs consist of one essential genetic determinant regulating the synthesis and action of florigen.

Interaction With Other Plant Hormones

Florigen acts synergistically with gibberellins during flowering. The distribution and the activity of florigen can also be controlled by cytokinins.

Environmental Factors Influencing Florigen Activity

Light, temperature, and day length—through which florigen synthesis and movement are guided—are major environmental factors.

Photoperiodism

The ability of florigen to mediate plants' responses to daylight duration makes it a factor in photoperiodic flowering.

Vernalisation

Although the cold period itself is not favourable for flowering, it has positive effects on florigen action.

Case Studies

Studies across species indicate florigen has its action via a wide array of functions and modes of action.

Examples Of Florigen Function In Different Plant Species

Arabidopsis thaliana

The Arabidopsis expresses FT protein responsible for the promotion of flowering by long days.

Rice (Oryza sativa)

Florigen controls flowering under short-day conditions in rice.

Tomato (Solanum lycopersicum)

Experiments with tomato plants revealed the molecular way in which florigen coordinates flowering with the environment.

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