Sepal initiation

Fig 9.2 Development of sepals, petals and carpels in Conostegia. (A), (E) C. icosandra (B) C. xalapensis (C) C. pittieri (D), (F) C. macrantha (G) C. rhodopetala (H) C. centronioides. (A) Young inflorescence with older apical flower and two lateral flowers with hracteoles. (B) Partial view of inflorescence with apical flower showing early petal initiation and lateral flower with sepal initiation. (C) Early initiation of gynoecial dome... 

Sepals initiate in a rapid, almost simultaneous, sequence or initiation is unidirectional (Fig 12.3B). However, sepals become rapidly equal in size with a valv-ate aestivation (Fig 12.3C-E). The apical part of the sepal is initially developed in a massive protuberance, which overtops the rest of the flower (Fig 12.3F). The broad upper section becomes covered with small trichomes on the margins (Fig 12.3E,F), spreading to the whole sepal surface (Fig 12.3G). The sepals bear one large or a pair of sessile glands on each side arising as lobes on the margins (Fig 12.3E,F). At maturity sepals are more equal in size and spread open or become reflexed. 

The perianth has a calyx and corolla in all three genera. In Nitraria and Peganum, the sepals are initiated in a clockwise or anticlockwise spiral sequence. In contrast, the five petals are initiated more or less simultaneously. In both genera, the second sepal is in median adaxial position as is common in core eudicots (this study Payer, 1857 Ronse De Craene, 2010 for Nitraria, also Baillon, 1873 for Peganum, also Eichler, 1878). The abaxial petal between sepals 1 and 3 (= petal 1) is slightly larger than the others at first, in both genera (this study Ronse De Craene et al., 1996). In Tetradiclis the first pair of sepals is in the median plane (Eichler, 1878). 

Fig 9.5 Flower morphology of Heterocentron elegans (A)-(B), Clidemia octona (C)-(F) and of Dissotis rotundifolia (G)-(ff). (A) Mature flower bud with four petals (removed) and eight stamens. (B) Detail of flower showing a style surrounded by an extension of the ovary wall at the base. The anthers are provided with basal auriculate appendages. (C) Development of sepal lobes surrounding petal primordia. (D) Initiation of stamens and carpels. Note the... 

Fig 11.5 A. celastrifolia, stamen initiation. Sepals and petals removed in all. (A) Frontal view of androecial ring-wall with first stamens formed (asterisks) alternating with the petals. (B) Lateral view of a hud with first formed stamens (asterisks). (C) Androecial ring-wall (circle) and first formed stamens (arrowheads) alternating with the petals. (D) Side view of somewhat older hud. Stamen primordia are formed in a centripetal pattern. 

Prenner, G. (2004c). New aspects in floral development of Papilionoideae initiated but suppressed bracteoles and variable initiation of sepals. Annals of Botany, 93, 537-545. 

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