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Flower

Induction Of Flowering

Many environmental cues signal a plant to produce flowers, and light is one of the most important of these. In many species, flowering is a photoperiodic response, in that it is controlled by the length of the light and dark periods to which the plant is exposed.

Some plants, such as Maryland mammoth tobacco, soybean, and hemp, are short-day plants, in that they flower in the spring and autumn when the days are shorter. Other plants, for example, spinach, mouse ear cress, and fuchsia, are long-day plants, in that they flower in the summer when the days are longer. Some plants, such as cucumber, corn, and garden peas, are day-neutral plants, in that they flower regardless of the daylength. Often, different varieties of the same species have different light requirements for flowering.

The dark period is as crucial as the light period for induction of flowering. In particular, when a short-day plant is exposed to short days, but given a pulse of light during the dark period, flowering is inhibited. When a long-day plant is exposed to short days but given a pulse of light during the dark period, flowering is promoted. Phytochromes are the photoreceptive plant pigments which detect these light pulses. Phytochromes also control other stages of plant growth and development, and phytochrome genes have been cloned and sequenced in many plant species.

Regrettably, plant physiologists have made little additional progress in understanding the mechanism of flower induction in recent years. Little is known about the biochemical reactions that follow from activation of phytochrome or how plants measure photoperiod. This is an area in which future botanists may make great progress.

Resources

Books

The American Horticultural Society. The American Horticultural Society Encyclopedia of Plants and Flowers. New York: DK Publishing, 2002.

Judd, Walter S., Christopher Campbell, Elizabeth A. Kellogg, Michael J. Donoghue, and Peter Stevens. Plant Systematics: A Phylogenetic Approach. 2nd ed. with CD-ROM. Suderland, MD: Sinauer, 2002.

Kaufman, P.B., et al. Plants: Their Biology and Importance. New York: Harper College Press, 1990.

Periodicals

Adams, K.L., et al. "Repeated, Recent and Diverse Transfers of a Mitochondrial Gene to the Nucleus in Flowering Plants." Nature 408 (2000): 354-357.


Peter A. Ensminger

KEY TERMS

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Anther

—The part of the stamen that produces pollen.

Carpel

—Female reproductive organ of flowers which is composed of the stigma, style, and ovary.

Filament

—Stalk of the stamen which bears the anther.

Ovary

—Basal part of the carpel which bears ovules and develops into a fruit.

Ovule

—Structure within the ovary which develops into a seed after fertilization.

Petal

—Whorl of a flower just inside the sepals that is often colored.

Sepal

—External whorl of a flower which is typically leaflike and green.

Stamen

—Male reproductive organ of flowers that produces pollen.

Stigma

—The part of the female organs of a plant flower (the pistil) upon which pollen lands in the first stage of fertilization.

Style

—A stalk that joins the pollen-receptive surface of the stigma, to the ovary of the female organ of a plant (i.e., the pistil).

Additional topics

Science EncyclopediaScience & Philosophy: Ferroelectric materials to Form and matterFlower - Study Of Flowers Throughout History, Parts Of The Flower, Evolution Of Flowers, Induction Of Flowering