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Santalales is an order of parasitic flowering plants that contains cryptically parasitic shrubs and trees as well as the more famous epiphytic parasites known as mistletoes. The epiphytic habit known as mistletoe applies to multiple groups that seem to have evolved independently from root parasitic Santalalean ancestors.

The group formerly known as the "Caryophyllids" once consisted of multiple orders and encompasses about 7% of flowering plant species. They are currently all lumped together into one large order, the Caryophyllales. One of the unifying characteristics of the core Caryophyllales is the presence of pigments known as betalains, which aren't present in any other flowering plant lineage. Betalains are named after the genus of beets (Beta) and give the roots of that plant their diagnostic color. Oddly, one of the few groups in the core Caryophyllales that produces anthocyanins instead of betalains is the nominate family, Caryophyllaceae.

Caryophyllales and Santalales don't group strongly with either the Rosids or Asterids and form a grade between the two groups, with Caryophyllales falling sister to the Asterids in the most well-supported analyses.

Santalales: (no families covered in class; just know the information about the order as a whole)

Caryophyllales:

Droseraceae (Sundew Family)

Polygonaceae (Buckwheat Family)

Cactaceae (Cactus Family)

Caryophyllaceae (Pink Family)

 

Order: Santalales

Santalales is a highly variable group of parasitic species ranging from shrubs and trees that cryptically attach their roots to other species to the mistletoes, an epiphytic parasite habit that has evolved within the order from root parasite ancestors multiple times. Tristerix aphyllus (Loranthaceae) is a mistletoe that parasitizes cacti and grows secretly inside their cortex until bursting forth from the cactus stem with brilliant red flowers. Balanophoraceae are particularly bizarre root parasites that lack chlorophyll at any stage of their life cycles and have reproductive structures that are nearly unrecognizable as flowers. Their genes have evolved with corresponding weirdness, and their placement with Santalales is still somewhat tentative.

Loranthaceae: Gaiadendron punctatum, (fruits); Psittacanthus sp.; Tristerix aphyllus, (2), (closeup of flowers), (front view); Tristerix corymbosus (Chile); Tristerix sp.

Misodendraceae: Misodendrum angulatum, (habit on Nothofagus); Misodendrum linearifolium, (fruit with staminodial filaments)

Santalaceae: Comandra umbellata Bastard Toadflax; Pyrularia pubera (2), (fruit) Buffalo Nut

(Formerly Viscaceae, now often nested within a broader Santalaceae): Arceuthobium vaginatum (2), (close) Pineland Dwarf Mistletoe; Phoradendron serotinum (on Georgia Oak), (inflorescences), (flowers close), (syrphid pollination), (berries) Eastern Mistletoe; P. villosum Oak Mistletoe; Dendrophthora squamigera

Balanophoraceae (questionably in Santalales): Corynaea crassa (habit with scales covering immature inflorescences), (haustorial tumor and emerging inflorescences), (closeup of expanding flowers), (flowering inflorescence), (flowers)

 

Order: Caryophyllales

Droseraceae: (Sundew Family) ~189 species

Identification characteristics: Members of this family are most easily recognized by their leaves, which are highly modified for carnivory. Most species in the family have numerous long, glandular hairs on the leaf suface that secrete a visible droplet of sticky fluid. Dionaea is an exception, with its well-known "flytrap" leaves. Another exception is Aldrovanda, an aquatic species that produces snap-traps like Dionaea to catch underwater invertebrates. Flowers are borne in determinant, helicoid inflorescences in most species. The flowers are generic eudicot flowers- 5 sepals, 5 petals, and 5 or 10 stamens that are all distinct or very nearly so. Three carpels constitute the superior ovary, which forms a capsule at maturity; in Drosera, each carpel usually has 2 styles, giving the false appearance of 6 carpels. If you're looking at the carpels to identify this distinctively carnivorous family, you're probably trying too hard.

Interesting stuff: If an unfortunate insect contacts the leaves of a sundew, it quickly becomes more and more stuck as it struggles to free itself. Sundew leaves then may slowly curl around the insect over the course of a few hours and secret digestive enzymes that allow the plants to obtain nitrogen and other nutrients. Venus Fly Trap (Dionaea muscipula) is the most famous of all carnivorous plants, with its very active trapping mechanism. The plants have "trigger" hairs on either half of their traps. Insects, attracted to the bright red color and sweet secretions inside the trap, must make contact with two of the hairs in order to spring the trap. An action potential is quickly transported to the joint between the trap and the rest of the leaf, and rapid water movement results in immediate closure of the trap (the plant has to have reflexes quicker than a fly!). The leaves of sundews and flytraps can be used more than once, although both must be replaced after about 3 uses. Droseraceae grow in wet, acidic areas, such as sphagnum bogs and sandy shores, where inorganic nutrient availability is low.

Examples: Aldrovanda vesiculosa Waterwheel Plant; Drosera burmannii (2), (3) Tropical Sundew; D. capensis (flower) Cape Sundew; D. capillaris Pink Sundew; D. paleacea Pygmy Sundew; D. rotundifolia (flower) Round-Leaved Sundew; D. tracyi (flower), (Red-banded Hairstreak prey), (fly prey); Dionaea muscipula, (trap), (trap showing trigger hairs), (with lizard prey), (silhouetted lizard prey), (with fly), (2), (flower), (inflorescences), (2), (flowers) Venus Flytrap

Polygonaceae: (Buckwheat Family) ~1,384 species

Identification characteristics: The most easily recognizable feature of Polygonaceae are the ochrea, the stipules which are fused into a thin, papery sheath around the swollen nodes of the plants. The leaves are alternate. Plants are herbaceous or sometimes may be trailing or twining vines, but ochrea are almost always present. The flowers of Polygonaceae are variable; most have 6 tepals (sometimes appearing as 3 sepals and 3 petals). 2 tepals may be fused, giving the appearance of a 5-tepaled flower. Stamens are variable ranging from 5 to 9. There is one superior ovary comprised of 2 or 3 fused carpels. An achene is eventually formed as the fruit.

Interesting stuff: Members of this family can be invasive in some habitats, and many are common garden and agricultral weeds (docks, knotweeds, etc,). Buckwheat (Fagopyrum) and Rhubarb (Rheum) are two useful members of the family.

Examples: Eriogonum parvifolium Seacliff Buckwheat; Fallopia cilinodis (inflorescence), (flower), (ochrea) Fringed Bindweed; Persicaria bistortoides Western Bistort; P. virginiana, (maturing achenes), (ochrea) Virginia Knotweed

Cactaceae: (Cactus Family) ~2,233 species

Identification characteristics: Although most people might think they know a cactus when they see it (or feel it) there are many other succulent plants that have the aspect of cacti, and many also possess imposing spines. The photosynthetic portion of a cactus is its stem (cladophyll), and cacti often have obvious patches on their pads or stems from which spines radiate. These patches are nodes with short side-shoots known as areoles which, in addition to/in place of producing spines sometimes produce irritating hairs known as glochids. Glochids and spines of cacti are modified leaves. Cactus-like Euphorbiaceae generally have paired stipular spines at every node where a leaf was originally present. The flowers of Cactaceae have numerous separate tepals, the lower-most of which may appear sepal-like. They also have numerous stamens and have a variable number of fused carpels that make up their inferior ovary, which forms a berry as the fruit at maturity.

Interesting stuff: Like many other succulents, cacti perform Crassulacean Acid Metabolism (CAM) by which they store carbon dioxide in organic acids at night and transport them away from the region of gas exchange. The carbon dioxide is then released from the acids and used to produce sugars through the Calvin Cycle during the daytime. This process helps minimize water loss and photorespiration, whereby oxygen binds to the crucial photosynthetic enzyme Rubisco and inhibits the Calvin cycle. Although cacti are generally regarded as desert plants, they may be found in prairies, beaches, glades, barrens, and many tropical species are epiphytes. Cactaceae is almost entirely endemic to the new world (one epiphyte is arguably native on the other side of the Atlantic), although some species have been introduced and become invasive in various other continents.

Examples: Carnegia gigantea (flower), (2) Saguaro; Cereus hildmannianus (2); Echinocereus rigidissimus (flower) Rainbow Hedgehog Cactus; E. triglochidiatus, (2), (3) Red Starspine Cactus; Echinopsis chilensis (red flowers are a parasitic mistletoe); Epiphyllum oxypetallum Dutchman's-Pipe Cactus; Lophophora diffusa (flowers); Opuntia engelmannii, (flower) Texas Prickly-Pear; O. humifusa Eastern Prickly-Pear; Rhipsalis baccifera Pencil Cactus; Schlumbergera hybrid (2) Easter Cactus Selenicereus grandiflorus (2), (3) Queen-of-the-Night.

Caryophyllaceae: (Pink Family) ~2,456 species

Identification characteristics: Caryophyllaceae are herbaceous and generally have opposite leaves. The stems are often slightly swollen at the leaf nodes. There are usually 5 sepals often fused into a calyx cup or tube. The 5 petals are distinct, and are often notched, sometimes very deeply so. The number of stamens varies, but is usually twice as many as the petals. There is one superior ovary formed from fusion of 2 to 5 carpels. The carpel count is often made evident by separate styles arising from the top of the single ovary. The fruit is almost always a capsule that opens by valves or teeth at the summit of the ovary.

Interesting stuff: The name "Pink Family" refers not to their color (although many members do have pink flowers), but rather to the notching at the ends of their petals (like the sewing term...e.g. pinking shears). Most plants use anthocyanins as their major flower pigments, but Caryophyllales instead possess a different class of pigments known as betalains. Caryophyllaceae have somehow reverted back to the use of anthocyanins, but the chemical processes by which these transitions took place are not known. The most economically important plants in Caryophylaceae are ornamentals such as Carnations (Dianthus) and Baby's Breath (Gypsophila).

Examples: Minuartia patula Pitcher's Stitchwort; M. uniflora (2), (closer) Oneflower Stitchwort; Silene acaulis (2) Moss Pink; S. polypetala (2), (flower) Fringed Campion; S. regia (2), (3) Royal Catchfly; S. stellata Starry Campion; S. virginica, (closer), (flower), (2) Fire Pink; Stellaria media Common Chickweed; S. pubera (flower) Star Chickweed.

Amaranthaceae: Chenopodium album Lamb's Quarters; Dysphania ambrosioides (flower) Mexican Tea

Montiaceae: Claytonia caroliniana (2), (3), (flower closeup) Carolina Spring Beauty; Claytonia virginiana (habit), (inflorescence), (flower closeup), (2) Spring Beauty; Phemeranthus mengesii, (2), (closeup) Menges' Fameflower

Phytolaccaceae: Phytolacca americana, (fruit) Pokeweed

Nepenthaceae: Nepenthes albomarginata; N. truncata

 

Order: Gunnerales (probably sister to all the Core Eudicots):

Gunneraceae: Gunnera insignis, (inflorescence) Poor-Man's Umbrella

 

 

 

 

 



 

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