What Is The Nature of Florigen

What Is The Nature of Florigen - Florigen and Flower...

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Florigen and Flower Stimulus By: Matthew Flack A long running question in the field of Plant Biology is the chemical nature of flowering. Many theories have come forth over the years, but the most promising is the discovery of the Florigen and more recently is genetic counterpart the Flowering Locus T (FT) gene. One alternative to the Florigen/Antiflorigen hypothesis is known as the ‘multifactorial control hypotheses’ which was proposed by Bernier in 1988. This hypothesis proposes that several different hormones and nutrient promote and inhibit each other to stimulate flowering at the shoot apical meristem. The theory also proposes that flowering variations between different plant species is due to genetic variation and the native environment of the plant. Another opposing theory is the ‘nutrient diversion’ hypothesis proposed by Sachs and Hackett which proposes that flowering is just a modification of the source/sink process in the plant in which more nutrients are pumped to meristem to stimulate flowering. Throughout the years there have been many experiments on Florigen which have studied its effects, movement, genetic composition, and universality among plant species. The flowering hormone concept is considered to have been conceived in 1865 by Julius Sachs who experimented on partially darkened Tropaeolum majus and Ipomoea purpurea plants. His experiment only allowed light onto some of the leaves of the plant, but he noticed that the darkened shoots and those in light both flowered. From this observation he concluded that the leaves in the light were producing a flowering complex which was transferred to the darkened shoots. This original experiment brought about the idea of a hormonal control of flowering, but more in depth experiments were performed after the discovery of photoperiodism in 1920 by Garner and Allard. Photoperiodism is the ability of plants to measure the length of periods of
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light, which created the distinction between short-day plants and long-day plants. Short-day plants stop flowering after the day length has exceeded a specific amount of time, while long-day plants flower after a certain amount of light exposure is achieved. In 1934 an experiment by Knott found that daylength was measured by the leaves, but the flower formation occurs in the shoot apical meristem. This proves that a signal created in the leaves must travel through the plant to the meristem to stimulate flowering, but at this point the nature of the signal was unknown. A real breakthrough came in 1936 when Chailakhyan showed that the signal can be transmitted from a flowering plant to a non flowering plant through grafting. Chailakhyan was the first to create the name Florigen for this mystery compound, which means flower-former. He defined Florigen as specific substances with a regulatory function, which was a vague description but it did isolate the fact that there is a mechanism in plants which regulates flowering. Along with the grafting of flowering and non flowering plants together, it was shown
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This note was uploaded on 05/14/2008 for the course PLSC 400 taught by Professor Deitzer during the Spring '08 term at Maryland.

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What Is The Nature of Florigen - Florigen and Flower...

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