4-28 arabidopsis genetics-flowering

4-28 arabidopsis genetics-flowering - ARABIDOPSIS GENETICS...

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ARABIDOPSIS GENETICS: FLOWERING LIFE 38.2; KLUG pg. 389-590 38.2.1 Apical meristems can become inflorescence meristems - The first visible sign of a transition to the flowering state may be a change in one or more apical meristems in the shoot system . During vegetative growth , an apical meristem continually produces leaves, auxiliary buds , and stem in a kind of unrestricted growth called indeterminate growth -If a vegetative apical meristem becomes an inflorescence meristem , it ceases production of leaves and auxiliary buds and produces other structures: smaller leafy structures called bracts , as well as new meristems in the angles between the bracts and the stem . These new meristems may also be inflorescence meristems , or they may be floral meristems , each of which gives rise to a flower . - Each floral meristem typically produces four consecutive whorls or spirals of organs—the sepals , petals , stamens , and carpels discussed earlier in the chapter—separated by very short internodes , keeping the flower compact. In contrast to vegetative apical meristems and some inflorescence meristems , floral meristems are responsible for determinate growth—growth of limited duration, like that of leaves. 38.2.2 A cascade of gene expression leads to flowering r Expression of a group of meristem identity genes initiates a cascade of further gene expression. cadastral genes , which participate in pattern formation—the spatial organization of the whorls of organs . Cadastral genes trigger the expression of floral organ identity genes , which work in concert to specify the successive whorls 38.2.3 Photoperiodic cues can initiate flowering - Environmental cues trigger the transition to the flowering state in many cases, depending on the genetic makeup of the species . The life cycles of flowering plants fall into three categories: annual , biennial , and perennial . Annuals complete their life cycle in one growing season. Biennials grow vegetatively for all or part of one growing season, then flower , form seeds , and die in the second growing season. Perennials live for a few to many growing seasons, during which both vegetative growth and flowering occur once the plants have reached sexual maturity. -Control of flowering and several other plant responses by the length of day or night is called photoperiodism . 38.2.4 Plants vary in their responses to different photoperiodic cues - Plants that flower in response to photoperiodic stimuli fall into several classes. Poinsettias, chrysanthemums, and ‘Maryland Mammoth’ tobacco are short-day plants (SDPs), which flower only when the day is shorter than a critical maximum . Thus, for example, we see chrysanthemums in nurseries in the fall, and poinsettias in winter. Spinach and clover are examples of long-day plants (LDPs), which flower only when the day is longer than a critical minimum .
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This note was uploaded on 09/02/2009 for the course BIO 315H taught by Professor Payne during the Spring '08 term at University of Texas.

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4-28 arabidopsis genetics-flowering - ARABIDOPSIS GENETICS...

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