Pinguicula, commonly known as the butterworts, is a genus of carnivorous flowering plants in the family Lentibulariaceae. They use sticky, glandular leaves to lure, trap, and digest insects in order to supplement the poor mineral nutrition they obtain from the environment. Of the roughly 80 currently known species, 13 are native to Europe, 9 to North America, and some to northern Asia. The largest number of species is in South and Central America.
Tropical butterworts either form somewhat compact winter rosettes composed of fleshy leaves or retain carnivorous leaves year-round. They are typically located in regions where water is least seasonally plentiful, as too damp soil conditions can lead to rotting. They are found in areas in which nitrogenous resources are known to be in low levels, infrequent or unavailable, due to acidic soil conditions.
Many butterworts cycle between rosettes composed of carnivorous and non-carnivorous leaves as the seasons change, so these two ecological groupings can be further divided according to their ability to produce different leaves during their growing season. If the growth in the summer is different in size or shape to that in the early spring (for temperate species) or in the winter (tropical species), then plants are considered heterophyllous; whereas uniform growth identifies a homophyllous species.
The leaf blade of a butterwort is smooth, rigid, and succulent, usually bright green or pinkish in colour. Depending on species, the leaves are between 2 and 30 cm (1-12") long. The leaf shape depends on the species, but is usually roughly obovate, spatulate, or linear. They can also appear yellow in color with a soft feel and a greasy consistency to the leaves.
Like all members of the family Lentibulariaceae, butterworts are carnivorous. The mechanistic actions that these plants use to lure and capture prey is through a means of sticky or adhesives substances that are produced by mucilage secreted by glands located on the leaf's surface. In order to catch and digest insects, the leaf of a butterwort uses two specialized glands which are scattered across the leaf surface (usually only on the upper surface, with the exception of P. gigantea and P. longifolia ssp. longifolia).
The second type of gland found on butterwort leaves are sessile glands which lie flat on the leaf surface. Once the prey is entrapped by the peduncular glands and digestion begins, the initial flow of nitrogen triggers enzyme release by the sessile glands. These enzymes, which include amylase, esterase, phosphatase, protease, and ribonuclease break down the digestible components of the insect body. These fluids are then absorbed back into the leaf surface through cuticular holes, leaving only the chitin exoskeleton of the larger insects on the leaf surface.
The holes in the cuticle which allow for this digestive mechanism also pose a challenge for the plant, since they serve as breaks in the cuticle (waxy layer) that protects the plant from desiccation. As a result, most butterworts live in humid environments.
As with almost all carnivorous plants, the flowers of butterworts are held far above the rest of the plant by a long stalk, in order to reduce the probability of trapping potential pollinators. The single, long-lasting flowers are zygomorphic, with two lower lip petals characteristic of the bladderwort family, and a spur extending from the back of the flower. The calyx has five sepals, and the petals are arranged in a two-part lower lip and a three-part upper lip. Most butterwort flowers are blue, violet or white, often suffused with a yellow, greenish or reddish tint. P. laueana and the newly described P. caryophyllacea are unique in having a strikingly red flowers. Butterworts are often cultivated and hybridized primarily for their flowers.
The diet will range depending on the taxonomy and size of the prey due to the plant's retention ability. These size limitations are known to be the main element influencing what prey sources this carnivorous plant can access They can also acquire nourishment from pollen and other plant parts that are high in protein, as other plants can become trapped on their leaves, thus, butterworts are both carnivorous and herbivorous plants. The diet consists of several species from the arthropod taxa, majority of their prey are insects that have wings and are able to fly. The luring, retaining, and seizing of prey is the first steps in the feeding procedure for carnivorous plants; the result of the process is absorption and digestion of nutrients sourced from these food supplies. Pinguicula species do not select their prey, as they passively accumulate them through methods of sticky, adhesive leaves. However, they do have the ability of visual attraction of their colorful leaves, which will increase the likelihood of luring and capturing a specific taxa.[better source needed] Pinguicula capture their food source/ prey by means of the mucilaginous, sticky substances produced by their stalk glands on the top of their leaf. Once the prey has become trapped in the peduncular glands, the sessile glands present will then produce enzymes needed to accomplish digestion and breaking down the digestible regions of the prey for their nutrients; taking in the fluids of the food source by means of cuticular holes present on the leaf's surface.
As well as sexual reproduction by seed, many butterworts can reproduce asexually by vegetative reproduction. Many members of the genus form offshoots during or shortly after flowering (e.g., P. vulgaris), which grow into new genetically identical adults. A few other species form new offshoots using stolons (e.g., P. calyptrata, P. vallisneriifolia) while others form plantlets at the leaf margins (e.g., P. heterophylla, P. primuliflora).
Butterworts are distributed throughout the northern hemisphere (map). The greatest concentration of species, however, is in humid mountainous regions of Central America (including Mexico) and South America, where populations can be found as far south as Tierra del Fuego. Australia and Antarctica are the only continents without any native butterworts.
The great majority of individual Pinguicula species have a very limited distribution. The two butterwort species with the widest distribution - P. alpina and P. vulgaris - are found throughout much of Europe and North America. Other species found in North America include P. caerulea, P. ionantha, P. lutea, P. macroceras, P. planifolia, P. primuliflora, P. pumila, and P. villosa.
In general, butterworts grow in nutrient-poor, alkaline soils. Some species have adapted to other soil types, such as acidic peat bogs (ex. P. vulgaris, P. calyptrata, P. lusitanica), soils composed of pure gypsum (P. gypsicola and other Mexican species), or even vertical rock walls (P. ramosa, P. vallisneriifolia, and most of the Mexican species). A few species are epiphytes (P. casabitoana, P. hemiepiphytica, P. lignicola). Many of the Mexican species commonly grow on mossy banks, rock, and roadsides in oak-pine forests. Pinguicula macroceras ssp. nortensis has even been observed growing on hanging dead grasses. P. lutea grows in pine flatwoods. Other species, such as P. vulgaris, grow in fens. Each of these environments is nutrient-poor, allowing butterworts to escape competition from other canopy-forming species, particularly grasses and sedges.
Butterworts need habitats that are almost constantly moist or wet, at least during their carnivorous growth stage. Many Mexican species lose their carnivorous leaves, and sprout succulent leaves, or die back to onion-like "bulbs" to survive the winter drought, at which point they can survive in bone-dry conditions. The moisture they need for growing can be supplied by either a high groundwater table, or by high humidity or high precipitation. Unlike many other carnivorous plants that require sunny locations, many butterworts thrive in part-sun or even shady conditions.
The first mention of butterworts in botanical literature is an entry entitled Zitroch chrawt oder schmalz chrawt ("lard herb") by Vitus Auslasser in his 1479 work on medicinal herbs entitled Macer de Herbarium. The name Zittrochkraut is still used for butterworts in Tirol, Austria.
It was only in the late 19th century that the carnivory of this genus began to be studied in detail. In a letter to Asa Gray dated June 3, 1874, Charles Darwin mentioned his early observations of the butterwort's digestive process and insectivorous nature. Darwin studied these plants extensively. S. J. Casper's large 1966 monograph of the genus included 46 species, a number which has almost doubled since then. Many exciting discoveries have been made in recent years, especially in Mexico. Another important development in the history of butterworts is the formation of the International Pinguicula Study Group, an organization dedicated to furthering the knowledge of this genus and promoting its popularity in cultivation, in the 1990s.
Butterworts are widely cultivated by carnivorous plant enthusiasts. The temperate species and many of the Mexican butterworts are relatively easy to grow and have therefore gained relative popularity. Two of the most widely grown plants are the hybrid cultivars Pinguicula 'Sethos' and Pinguicula 'Weser'. Both are crosses of Pinguicula ehlersiae and Pinguicula moranensis, and are employed by commercial orchid nurseries to combat pests.
Butterworts also produce a strong bactericide which prevents insects from rotting while they are being digested. According to Linnaeus, this property has long been known by northern Europeans, who applied butterwort leaves to the sores of cattle to promote healing. Additionally, butterwort leaves were used to curdle milk and form a buttermilk-like fermented milk product called filmjölk (Sweden) and tjukkmjølk (Norway). 041b061a72