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Fig. 24.3 T&Z3

Fig. 24.3 T&Z3. Normal Floral Organ Identity. Organs (LDOs) are always produced by the Flower Shoot Apical Meristem (Flower SAM) in the following order, from lower/outer to upper/inner: Sepals Petals Stamens Carpels. Names of Flower Organs.

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Fig. 24.3 T&Z3

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  1. Fig. 24.3 T&Z3 Normal Floral Organ Identity Organs (LDOs) are always produced by the Flower Shoot Apical Meristem (Flower SAM) in the following order, from lower/outer to upper/inner: Sepals Petals Stamens Carpels

  2. Names of Flower Organs Individual Collectively, Distinct Organ or Connate Carpel Gynoecium (G), Ovary, Pistal Stamen Androecium (A) Petal Corolla (Co, C) Perianth (P) Sepal Calyx (Ca, K) If the organs of the two whorls/spirals of the Perianth are not differentiated from each other (that is, are both showy appear similar to each other), they may be called Tepals (T) or simply P

  3. When you cannot easily count the organs Number of Petals usually equals number of Sepals (Sepals are usually easy to see from below the flower) Sepals and Petals are usually Alternate/Rotationally offset (If true for part of its circumference, true for entire flower)

  4. wt ap2 pi ag1 Fig. 2 Meyerowitz 2002 Homeotic Mutants that Transform the Identity of Adjacent Whorls B B B AC CA C A S P St C C St St C S S C C [S P P S] n Wild Type A is Null B is Null C is Null Arabidopsis

  5. The ABC Model of Floral Organ Identity The ABC Model based only on phenotypes of single mutants Each Function acts in two adjacent whorls Functions include Organ Identity and, for A and C, inhibition of each others function

  6. SepalsPetals StamensCarpels C A B C A B C A B C A B YSUP AP3+PIAP3+PI AP3+PIAP3+PI LUG+SEULUG+SEU LUG+SEU LUG+SEU AP1 SEP3AP1 SEP3 AP1 SEP3 AP1 SEP3 AG AG AG AG AP2+BLR AP2+BLR AP2 AP2 LFY+WUS LFY+WUS AG AG ABCE Model: RegulatorsY(inhibitsAP3+PI),BLR(activates AP2),andLFY+WUS(activates AG) are differentially expressed

  7. CarpelsStamensStamensCarpels C A B C A B C A B C A B YSUP AP3+PIAP3+PI AP3+PIAP3+PI LUG+SEULUG+SEU LUG+SEU LUG+SEU AP1 SEP3AP1 SEP3 AP1 SEP3 AP1 SEP3 AG AG AG AG AP2+BLR AP2+BLR AP2AP2 LFY+WUS LFY+WUS AG AG Why ap2 lacks both A Functions: Expansion of AGinto Whorls 1 and 2 inhibits the Specification Function ofAP1

  8. Tepals in Monocots First two whorls are identical, looking like two whorls of Petals, three organs in each whorl Expression of ABC Genes indicates that both whorls are Petals: the whorl of Sepals has been transformed into a whorl of Petals

  9. Imperfect Flowers: Male and Female Flowers Studies of the development of the whorls in Male and Female flowers indicate that both male and female whorls start development, but either the male or female whorl aborts, resulting in a unisexual (imperfect and incomplete) flower There is an extensive taxonomy based on the types of flowers (hemaphorditic vs unisexual) on individuals and in populations monoecious (one house): male and female flowers on same plant dioecious (two houses): male and female flowers on different plants

  10. Floral Symmetry Actinomorphic: Radially Symmetric (Actually Rotationally Symmetric) Probably the Ancestral State Zygomorphic: Bilaterally Symmetric Local Inhibition of Organ Development and/or Differential Growth of Organs, resulting in one or two mirror planes If any part of the flower is even weakly zygomorphic the entire flower is considered to be zygomorphic Irregular: No obvious Symmetry

  11. All Ovaries start out Superior (4th Whorl) The first three whorls may be elevated on an outgrowth of the receptacle on which they are borne/inserted This outgrowth is called an Hypanthium It may be entirely adnate (fused) to with the ovary, adnate to the ovary only in the ovary’s basal region, or entirely distinct (free) Hypogynous: Apparent insertion of the first 3 whorls below the gynoecium Perigynous: Apparent insertion of the first 3 whorls at level of gynoecium Epigynous: Apparent insertion of the first 3 whorls above the gynoecium Receptacle Hypanthium 23.11 Stern9

  12. Agree Agree Duh? A More Narrow Definition of an Hypanthium MS Simpson (and many taxonomists?): An hypanthium is not an hypanthium if it is adnate (fused) to the ovary. It is an hypanthium only if it is distinct (free of the ovary). Have not discovered how they think the corolla and androecium crawled up the sides of the ovary.

  13. RAB Glossary: A Broad Definition of an Hypanthium Hypanthium: May be adnate to ovary (epigyny) or free from ovary (perigyny). Superior ovary: Hypanthium adnate to ovary for less than ¼ the length of the ovary. Inferior ovary: Hypanthium adnate to the ovary for ¾ or more of its length. Sensible, and the Keys and Descriptions of Rosaceae use these definitions. But at least one lead to some taxa of Rosaceae does not.

  14. Partial to complete Connation/Fusion of Carpels Minimum Number of carpels can be inferred from whichever is the larger number: number of locules, number of lobes, number of (paired) rows of ovules, number of styles, or number of stigmas. Warning: In some taxa, a carpel develops a false septum, resulting in two pseudo-locules

  15. Close Carpels before Fusing Them Fuse Carpels before Closing Them

  16. Ovaries from Fused Carpels nonseptate septate axial parietal 3 Carpellate 3 Loculate 3 Septa 3 Carpellate 1 Loculate 0 Septa basal marginal axial parietal free central Walters and Keil marginal axial parietal free central apical

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