|Caryophyllaceae - Campion Family
Bladder Campion (Silene vulgaris) is immediately recognisable with its hollow, bladder-like flower
tube (corolla) and surrounding tube of fused sepals (calyx tube). It is a fascinating example of a
curious biological phenomenon - it is gynodioecious. Gynodioecious plants come in two different
genders: female individuals (with reduced and sterile male parts) and hermaphrodite individuals.
The hermaphrodites have longer anthers and longer staminal filaments and smaller ovules than
the female plants. They also have longer petals and wider corollas. This raises interesting
questions concerning the evolutionary advantage of gynodioecy.
In an attempt to understand the significance of this phenomenon research has examined the
various trade-offs in the two forms (Dykstra et al. 2009. Int. J. Plant Sci. 170(5): 575–583). For
example, in hermaphrodites the ovule size is inversely proportional to anther length, so anthers
tend to be shorter when ovules are larger and vice versa, suggesting that male and female
function are competing for the same resources. Internode length in hermaphrodites was also
inversely proportional to ovule number, suggesting that plants growing in shade (which elongate
their internodes in an attempt to reach more light) invest fewer resources on female reproduction,
whilst male reproduction remains unaffected. In contrast, in females these correlations are not
found, but instead ovule size is inversely proportional to ovule size, suggesting that flowers with
more ovules have smaller ovules, indicating a limited resource allocation. In female plants,
internode length correlates with ovule number, meaning that taller plants tend to have more
ovules, so female reproductive capacity is not being compromised in plants growing in shade.
The Caryophyllaceae (Campion family) include White Campion (Silene latifolia, above), Red Campion
and Bladder Campion (Silene vulgaris). the infloresecnce is a cyme, meaning that it has sympodial
branching with branches terminating in flowers. The cyme has either a single main axis (monochasial
cyme) or two main axes (dichasial cyme). Note the tube of fused sepals enclosing the tube of petals.
Above: the bracteoles of campions are well-developed. These are leaf-like structures (bracts)
subtending each flower stalk or pedicel. (Bracts proper subtend the flower itself). The contorted
(convolute) imbricate aestivation is clearly visible in the flower bud on the right. Aestivation
(prefloration) is the folding of flower parts into the bud. Imbricate means the edges (of the petals in
this case) overlap and convolute or contorted means that each petal has one edge out (over the
in-tucked edge of the preceding petal) the other one tucked in to the next petal.
Above: the typical campion petal shape is readily apparent, consisting of a narrowed basal part or
petal claw, and a two lobed or bifid apex. A protruding appendage is associated with the top of
the claw, together forming a protruding rim. Some researchers consider the petals to be modified
stamens in Caryophyllaceae. The stamens of this family typically fuse into a stamen tube. There
are typically ten stamens, five aligned with the five sepals (antesepalous) and five aligned with the
five petals (antepetalous). The fruit are dry and dehiscent, splitting open when ripe.
Article updated: 23rd August 2015