The Caryophyllales takes its name from the family Caryophyllaceae (pinks, carnations) and is an extensive group of 26 families of flowering plants with around 12,500 species including the succulent plant families Aizoaceae (mesembs, vygies), Cactaceae (cacti), Didieraceae and Portulacaceae (purslanes) and the carnivorous plant families Droseraceae (sundews, venus flytrap) and Nepenthes (pitcher plants). The Caryophyllales also includes important horticultural and agricultural crops: beet, bougainvillea, Caryophyllaceae (carnations and pinks), plumbago, rhubarb and spinach. Many members of the order grow in marginal habitats such as deserts and salt marshes.
Characteristic of the group is the basal or free central arrangement and attachment of ovules within the ovary so that the developing seeds are attached to the floor or to a central pillar not connected to the ovary wall by partitions. Seeds therefore become located in the centre of the mature fruit. Hence the name Centrospermae (central seeds} for a similar group of plant families in earlier taxonomic treatments.
Within the seeds the embryo is not centrally located, but formed around the outer edge of the seed. The nutritional material in the seed's centre is not formed from the embryo sac (triploid endosperm) as in seeds of most flowering plants but made with diploid perisperm derived from part of the ovule surrounding the gametophyte.
Betalain pigments are also characteristic of the Caryophyllales as is absence of anthocyanin pigments found in other families of flowering plants. Betalains are responsible for the red or violet colouration of some cacti when stressed and the red pigment in beetroot. Paradoxically, Betalain pigments are absent from the two families Caryophyllaceae and the smaller family Molluginaceae and present in some higher fungi. Betalains and anthocyanins never occur in the same plant. Ferulic acid is present throughout the Caryophyllales.
Sea Sandwort - Honckenya peploides