Caryophyllaceae

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Caryophyllaceae

Description

For practical reasons the perianth is here referred to as consisting of sepals and petals. For a discussion of these structures see below, under Morphology. Annual or perennial herbs, rarely dwarf shrubs or small bushes. Leaves opposite, rarely spirally arranged, sometimes apparently in whorls, entire, often connate at the base; — The leaves are opposite and decussate with very few exceptions; they are un-divided and usually have an entire margin. They are sessile or petiolate, free at the base (Paronychioideae) or connate (in Caryophylloideae and some Alsinoideae). In many Alsinoideae and Paronychioideae they are apparently whorled due to the production of axillary short-shoots. Succulent leaves are found in several genera. There is a wide range of leaf shapes from grass-like to needle-shaped and thorny to broadly ovate and circular, but the narrow leaf type is the most common. The buds in the axil of a leaf pair develop often unequally and frequently a single leaf instead of a leaf pair is found under the flower or the inflorescence. Stipules are found in the Paronychioideae but wanting in the two other subfamilies; they are usually scarious, white or brownish.
Inflorescence cymose, usually dichasial, sometimes monochasial, lax, or condensed, many- or few-flowered, rarely flowers solitary. — The inflorescences are always cymose. Rarely the stem is terminated by a single flower as in some species of Dianthus and Silene as the result of reduction. Usually the inflorescence is a thyrse composed of dichasia. This again may be lax or dense and head-like. Through suppression the inflorescence may become spike-like as in e.g. Silene gallica. Bracts are usually present. In Dianthus an epicalyx is formed by several pairs of bracteoles subtending the flower.
Flowers actinomorphic, bisexual or sometimes unisexual (dioecious, monoecious, or polygamous), 5- or 4-merous. — The flowers are always actinomorphic with the single exception of the Mediterranean Drypis spinosa in which the flower is slightly zygomorphic. Many small-flowered species, particularly in the Paronychioideae, are ± perigynous, while the Caryophylloideae and most of the Alsinoideae are hypogynous. The flowers have been interpreted as containing a perianth, the outer leaves of which are the green or scarious sepals, followed by a whorl arisen by ‘dédoublement’ of the outer whorl of the androecium. They alternate with the sepals and are divided into an exterior petaloid part, here named the petals, and an inner part being the normal, fertile stamens. In some genera the stamens of the outer staminal whorl are attached to the ‘petals’. In this revision the terms sepals and petals have been used throughout and stamens with reduced, non-functional anthers are called staminodes.

The sepals in the Paronychioideae are often provided with a dorsal, subapical appendage. In Caryophylloideae the sepals are connate and form a tube with shorter or longer free apical parts (teeth). The petals are entire or deeply bilobed or lacerate (Dianthus). The taxa with large flowers have usually two whorls of stamens, while many small-flowered species, particularly in the groups with free sepals, have reductions in the androecium to one whorl opposite the sepals; in this whorl again reductions can take place. Some small-flowered species e.g. in the genera Scleranthus and Stellaria have a variable number of stamens.

The ovary is composed of 2-5(-10) carpels, alternating or opposite to the stamens of the inner whorl; it is sometimes borne on a gynophore. It is usually unilocular, but may be divided in the lower part. The placentation is central or basal.
Petals (4-)5, free, differentiated in a short or long claw, a limb, and sometimes coronal scales; Stamens in two whorls of 5, sometimes fewer, often apparently obdiplo- stemonous; Fruit most often a capsule, dehiscing by teeth, rarely a berry or an achene. Seeds few to many, rarely one, small;

Distribution

Asia-Tropical: mountains of New Guinea: present temperate and subtropical zones of the northern hemisphere, with many representatives in the montane and alpine regions and with main centres in the Mediterranean and in the dryer parts of West Asia: present
The family consists of about 85 genera and 2,200 species. More than half of the species belong to one of the six large genera, Silene (700), Dianthus (300) Arenaria (150), Gyp-sophila (150), Stellaria (150), and Cerastium (100), all of which are represented in Malesia by indigenous or introduced species. The greatest diversity is found in the temperate and subtropical zones of the northern hemisphere, with many representatives in the montane and alpine regions and with main centres in the Mediterranean and in the dryer parts of West Asia. They are generally rare in the tropics, and among the 16 genera represented in Malesia, at least 6 are introduced. There are some rare endemisms (see Cerastium, Polycarpon, Sagina), particularly in the mountains of New Guinea

Pollination

The flowers are rarely homogamous as in e.g. Scleranthus. In most genera the flowers are dichogamous and protandrous. There are, however, considerable variations also within the species. Centripetal as well as centrifugal movements of the filaments have been demonstrated, first by the antisepalous stamens, later by the antipetalous ones. These movements will often lead to selfpollination.

The Alsinoideae usually have small, unspecialised, white or greenish flowers in which the nectar is easily accessible. Protandry is common but protogyny has been observed in e.g. Drymaria. There is a wide range of visiting insects, even if bees and flies are dominant pollinators. Many of the very small-flowered species in genera as e.g. Sagina and Arenaria are rarely visited and selfpollination must be predominant. In many species of Cerastium, Sagina and Spergularia the flowers remain closed in cold and overcast weather and autogamy is then the rule, but also in sunny weather this is common through the staminal movements. Cleistogamous flowers have been found in very few species of Holosteum, Minuartia and Stellaria. In the Paronychioideae similar modes of pollination occur; here also autogamy and cleistogamous flowers have been found.

In the Caryophylloideae, with their ± long tubular calyx, the nectar is placed deep down in the flower and is only accessible for insects with a long proboscis, furthermore the entrance may be closed by the coronal scales. The flowers are larger and showy in white or red colours, and often the plants produce a considerable amount of flowers at one time. Many species have also a strong scent particularly in the evening, thus attracting Lepidoptera. But also bees and some Syrphidae and even mosquitos have been found as pollinators. From North America bird pollination has been reported. For Silene otites wind pollination has been suggested.

Dispersal

Most Caryophyllaceae have no particular dispersal mechanisms, the seeds are simply shed from the open capsule over a longer period. In some Silenoideae the capsules open and close periodically according to the weather conditions; they close under moist conditions. In several species the pedicel is curved back after anthesis. In some species of Moehringia the seeds have a strophiolum that functions as an elaiosome; these species have myrmecochory. Splash-cup dispersal is reported in Sagina species in which the capsules open when wetted. Anemochory is found in species with inflated calyx and in species of e.g. Spergularia with winged seeds. In some small-flowered species of Paronychia and related genera parts of the infructescence break off and are dispersed in ± spherical, entangled bodies (windrollers). In species with a viscid persistent calyx, as e.g. within the Silenoideae, dispersal by various animals may be of importance. The rare berry-fruited taxa (not found in Malesia) have endo-ornithochorous dispersal. The seeds of some species of Drymaria are provided with stellate hairs and hooks and probably have epizoic dispersal.

Anatomy

One of the most remarkable characters that the Caryophyllaceae share with many other families within the Caryophyllales, is the presence of concentric rings of xylem and phloem or of distinct vascular bundles occurring in roots and stems. These features have been found in Polycarpaea, Polycarpon, Silene, and Spergula among the genera found in Malesia.

The stomata belong in general to the so-called caryophyllaceous or diacytic type, i.e. the stoma is enclosed by a pair of subsidiary cells whose common wall is at right angles to the guard cells. There are, however, many exceptions in genera as e.g. Arenaria, Cerastium, and Stellaria, where stomata in some species are found to belong to the cruciferous or anisocytic type, in which the stoma is surrounded by three cells of which one is distinctly smaller than the other two.

The family shares a number of ultrastructural and micromorphological characters with the other members of the Caryophyllales. Thus the sieve-element plastids belong to a type containing protein but no starch. The protein is arranged partly as concentric threads, partly as a central crystalloid body.

Taxonomy

The Caryophyllaceae have traditionally been divided into three subfamilies. Often the Paronychioideae are treated as a separate family Paronychiaceae. The principal differences between the three have been defined as follows.
  1. Paronychioideae: Leaves stipulate. Sepals free or only joined at the base, often with a small, dorsal, subapical appendage. Petals small or absent. Stamens usually free to the base, the nectary usually forming a ring below the filament base and placed in the wall of the hypanthium. Styles often fused at the base or for more than 1/2. In Malesia: Drymaria, Polycarpaea, Polycarpon, and Spergularia.
  2. Alsinoideae: Leaves exstipulate. Sepals free or rarely joined at the base, without dorsal appendages. Petals usually present, with a short or inconspicuous claw; episepalous stamens often with a nectary gland at the abaxial base. Styles usually free. In Malesia: Arenaria, Cerastium, Myosoton, Sagina, Scleranthus, and Stellaria.
  3. Caryophylloideae (Silenoideae): Leaves exstipulate. Sepals joined to a tubular calyx for most of their length, without any apical appendage. Petals large, divided into a long claw and a distinct lamina; episepalous stamens without nectary glands at the abaxial base. Anthophore often present in the form of a prolonged internode between calyx and corolla. Styles free. In Malesia: Dianthus, Gypsophila, Lychnis, Saponaria, Silene, and Vaccaria.

Several recent authors working on the taxonomy and phylogeny of the family are, however, of the opinion, that the distinction between the two first subfamilies cannot be maintained, and various authors circumscribe them differently.

Several authors have studied the affinities of the order Caryophyllales during the last decades. There is little doubt that the family Caryophyllaceae should be included in the order even if it lacks the characteristic betalaïns and instead produces anthocyanins. This is also the case with the small family Molluginaceae which several authors have taken as a sign of relationship between the two. However, Retting et al. (1992), in their phylogenetic analysis of the Caryophyllales, find that even if these two families are the only ones in the order that do not produce betalaïns, “they are neither closely allied nor basal to other elements of the order.”

Cytology

The Caryophyllaceae of the temperate and subtropical zones of the northern hemisphere are well known with regard to their chromosome numbers, but none of the endemic, montane and alpine Malesian (New Guinean) species have been studied cytologically. A long series of basic chromosome numbers have been found from x = 5 to x = 19, the most common numbers being x = 6 or 12. Polyploidy as well as aneuploidy have been demonstrated in numerous genera, and infraspecific polyploidy has been found in many species. There is also a considerable variation in chromosome morphology. Most commonly, however, the chromosomes are rather small and undifferentiated. Within the Paronychioideae the most common basic numbers are x = 8 and x = 9. In the Caryophylloi-deae most genera have x = 12. Most variable are the Alsinoideae where almost all basic numbers between 6 to 19 have been reported. High numbers have been found in Silene, where 2n = 192 and in Cerastium, where 2n = 144 have been counted. All introduced and weedy species in Malesia have been studied. Sex chromosomes have been found in Silene sect. Melandriformes and accessory chromosomes in Silene and Vaccaria.

Uses

Few species in this large family have any economic importance. Some species within the Caryophylloideae have been the base for breeding a number of very popular ornamentals mostly grown in temperate or subtropical climates, and species of Silene and Dianthus have found their way to Malesian gardens at higher altitudes. The presence of saponins in genera as Saponaria has been exploited particularly in earlier times; there is, however, no record of such uses in Malesia as far as known to the author. The seeds of Spergula and Spergularia, rich in starchy perisperm, have been used in the diet in prehistoric times in some parts of the world, but not in Southeast Asia.

Phytochemo

Chemically the Caryophyllaceae are deviating from most other members of the order Caryophyllales in having anthocyanins instead of betalaïns. In several genera saponins have been found, e.g. in Saponaria. Calcium oxalate is usually accumulated in the form of large conspicuous cluster-crystals, but also crystal-sand and solitary crystals are found. Other chemical characters, which the family shares with other Caryophyllales, are the occurrence of ferula acid and pinitol.