AnAPETALA3homolog controls both petal identity and floral meristem patterning inNigella damascenaL. (Ranunculaceae)

The vegetative apex was a low dome consisting of two layers of tunica surmounting a very small corpus. Foliar primordia originated as periclines in the flanks of T2. The transition apex became first a steep cone and then a hemisphere. All floral primordia—the two bracts, the two sepals, the several whorls of petals, the several whorls of stamens, and the carpels—originated in the manner of leaves, as periclines in T2 on the flanks of the apex. All appendages, including carpels, were therefore lateral. In the early transition, the apex had a brief stage in which there were three tunica layers, but the inner one was lost with the onset of the sepals. The bracts and the first sepal continued the normal positions of primordia for the vegetative phyllotaxy of 3/8, but with the second sepal, this phyllotaxy was lost, and petals, stamens, and carpels were produced in whorls. While leaves, bracts, sepals, and petals were produced in acropetal sequence, stamens were produced in basipetal sequence, and carpels appeared simultaneously. After carpels were formed, the rest of the floral apex underwent a brief period of expansion growth, achieving a diameter comparable to that of a shoot apex, but its substance was eventually incorporated into the carpel margins, which later produced the ovules. This agrees with the determinate nature of the floral apex. During the development of the first series of floral organs, the floral apex underwent continued increase in area, finally achieving a diameter several times that of the vegetative shoot apex. Its size and form were such that they were compared to those of some inflorescence apices. After development of the first series of floral organs, the subjacent tissues to the floral meristem underwent divisions and elongation at right angles to the axis, causing at first a flattening of the meristem, and eventually a cup-shaped form, with the carpels attached in the bottom of a bowl. The mature flower was thus perigynous, but this development arose quite differently from the perigyny as it is known from ontogenetic studies in the Rosaceae.

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Ovule is a lateral organ finally differentiated from the terminating floral meristem in rice

Developmental Biology ◽

10.1016/j.ydbio.2010.12.006 ◽

2011 ◽

Vol 351 (1) ◽

pp. 208-216 ◽

Cited By ~ 32

Author(s):

Shinichiro Yamaki ◽

Yasuo Nagato ◽

Nori Kurata ◽

Ken-Ichi Nonomura

Keyword(s):

Floral Meristem ◽

Lateral Organ

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PETAL LOSS gene regulates initiation and orientation of second whorl organs in the Arabidopsis flower

Development ◽

10.1242/dev.126.24.5635 ◽

1999 ◽

Vol 126 (24) ◽

pp. 5635-5644 ◽

Cited By ~ 1

Author(s):

M.E. Griffith ◽

A. da Silva Conceicao ◽

D.R. Smyth

Keyword(s):

Full Range ◽

Genetic Modifier ◽

Mutant Phenotype ◽

New Class ◽

Petal Identity ◽

Organ Identity ◽

Major Disruption ◽

The Mean ◽

B Class Genes ◽

Floral Whorl

PETAL LOSS is a new class of flower development gene whose mutant phenotype is confined mostly to the second whorl. Two properties are disrupted, organ initiation and organ orientation. Initiation is frequently blocked, especially in later-formed flowers, or variably delayed. The few petals that arise occupy a wider zone of the flower primordium than normal. Also, a minority of petals are trumpet-shaped, thread-like or stamenoid. Studies of ptl combined with homeotic mutants have revealed that the mutant effect is specific to the second whorl, not to organs with a petal identity. We propose that the PTL gene normally promotes the induction of organ primordia in specific regions of the second floral whorl. In ptl mutants, these regions are enlarged and organ induction is variably reduced, often falling below a threshold. A dominant genetic modifier of the ptl mutant phenotype was found in the Landsberg erecta strain that significantly boosts the mean number of petals per flower, perhaps by reinforcing induction so that the threshold is now more often reached. The second major disruption in ptl mutants relates to the orientation adopted by second whorl organs from early in their development. In single mutants the full range of orientations is seen, but when B function (controlling organ identity) is also removed, most second whorl organs now face outwards rather than inwards. Orientation is unaffected in B function single mutants. Thus petals apparently perceive their orientation within the flower primordium by a mechanism requiring PTL function supported redundantly by that of B class genes.

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A new family of DNA binding proteins includes putative transcriptional regulators of theAntirrhinum majus floral meristem identity geneSQUAMOSA

MGG Molecular & General Genetics ◽

10.1007/bf02191820 ◽

1996 ◽

Vol 250 (1) ◽

pp. 7-16 ◽

Cited By ~ 15

Author(s):

Joachim Klein ◽

Heinz Saedler ◽

Peter Huijser

Keyword(s):

Dna Binding ◽

Binding Proteins ◽

Transcriptional Regulators ◽

Dna Binding Proteins ◽

Floral Meristem ◽

Floral Meristem Identity ◽

New Family ◽

Meristem Identity

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Floral development of Potamogeton densus

Canadian Journal of Botany ◽

10.1139/b73-079 ◽

1973 ◽

Vol 51 (3) ◽

pp. 647-656 ◽

Cited By ~ 29

Author(s):

U. Posluszny ◽

R. Sattler

Keyword(s):

Floral Development ◽

The Other ◽

Floral Meristem ◽

Developmental Sequence ◽

Initial Activity ◽

The Third ◽

Stamen Primordia ◽

Procambial Strand ◽

Inflorescence Axis ◽

Rates Of Growth

The floral appendages of Potamogeton densus are initiated in an acropetal sequence. The first primordia to be seen externally are those of the lateral tepals, though sectioning young floral buds (longitudinally, parallel to the inflorescence axis) reveals initial activity in the region of the lower median (abaxial) tepal and stamen at a time when the floral meristem is not yet clearly demarcated. The lateral (transversal) stamens are initiated simultaneously and unlike the median stamens each arises as two separate primordia. The upper median (adaxial) tepal and stamen develop late in relation to the other floral appendages, and in some specimens are completely absent. Rates of growth of the primordia vary greatly. Though the lower median tepal and stamen are initiated first, they grow slowly up to gynoecial inception, while the upper median tepal appears late in the developmental sequence but grows rapidly, soon overtaking the other tepal primordia. The four gynoecial primordia arise almost simultaneously, although variation in their sequence of inception occurs. The two-layered tunica of the floral apices gives rise to all floral appendages through periclinal divisions in the second layer. The third layer (corpus) is involved as well in the initiation of the stamen primordia. Procambial strands develop acropetally, lagging behind primordial initiation. The lateral stamens though initiating as two primordia each form a single, central procambial strand, which differentiates after growth between the two primordia of the thecae has occurred. A great amount of deviation from the normal tetramerous flower is found, including completely trimerous flowers, trimerous gynoecia with tetramerous perianth and androecium, and organs differentiating partially as tepals and partially as stamens.

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