Bladder Vine

Bladder Vine

Succulentopedia

Dischidia vidalii (Kangaroo Pocket)

Dischidia vidalii (Kangaroo Pocket) is a very odd and interesting epiphytic climber. The leaves are small, thick, fleshy, oval-shaped and…


Contents

  • 1 Trapping mechanisms
    • 1.1 Pitfall traps
    • 1.2 Flypaper traps
    • 1.3 Snap traps
    • 1.4 Bladder traps
    • 1.5 Lobster-pot traps
    • 1.6 Combination traps
    • 1.7 Borderline carnivores
  • 2 Evolution
  • 3 Ecology and modeling of carnivory
  • 4 Conservation threats
  • 5 Classification
    • 5.1 Dicots
    • 5.2 Monocots
  • 6 Cultivation
  • 7 Medicinal uses
  • 8 Cultural depictions
  • 9 References
  • 10 Further reading
  • 11 External links

Five basic trapping mechanisms are found in carnivorous plants. [14]

  1. Pitfall traps (pitcher plants) trap prey in a rolled leaf that contains a pool of digestive enzymes or bacteria.
  2. Flypaper traps use a sticky mucilage.
  3. Snap traps utilise rapid leaf movements.
  4. Bladder traps suck in prey with a bladder that generates an internal vacuum.
  5. Lobster-pot traps, also known as eel traps, force prey to move towards a digestive organ with inward-pointing hairs.

These traps may be active or passive, depending on whether movement aids the capture of prey. For example, Triphyophyllum is a passive flypaper that secretes mucilage, but whose leaves do not grow or move in response to prey capture. Meanwhile, sundews are active flypaper traps whose leaves undergo rapid acid growth, which is an expansion of individual cells as opposed to cell division. The rapid acid growth allows the sundew tentacles to bend, aiding in the retention and digestion of prey. [15]

Pitfall traps Edit

Characterised by an internal chamber, pitfall traps are thought to have evolved independently at least six times. [6] This particular adaptation is found within the families Sarraceniaceae (Darlingtonia, Heliamphora, Sarracenia), Nepenthaceae (Nepenthes), Cephalotaceae (Cephalotus), and Eriocaulaceae (Paepalanthus). Within the family Bromeliaceae, pitcher morphology and carnivory evolved twice (Brocchinia and Catopsis). [6] Because these families do not share a common ancestor who also had pitfall trap morphology, carnivorous pitchers are an example of convergent evolution.

A passive trap, pitfall traps attract prey with nectar bribes secreted by the peristome and bright flower-like anthocyanin patterning within the pitcher. The linings of most pitcher plants are covered in a loose coating of waxy flakes which are slippery for insects, causing them to fall into the pitcher. Once within the pitcher structure, digestive enzymes or mutualistic species break down the prey into an absorbable form for the plant. [7] [16] Water can become trapped within the pitcher, making a habitat for other flora and fauna. This type of 'water body' is called a Phytotelma.

The simplest pitcher plants are probably those of Heliamphora, the marsh pitcher plant. In this genus, the traps are clearly derived from a simple rolled leaf whose margins have sealed together. These plants live in areas of high rainfall in South America such as Mount Roraima and consequently have a problem ensuring their pitchers do not overflow. To counteract this problem, natural selection has favoured the evolution of an overflow similar to that of a bathroom sink—a small gap in the zipped-up leaf margins allows excess water to flow out of the pitcher. [ citation needed ] [17]

Heliamphora is a member of the Sarraceniaceae, a New World family in the order Ericales (heathers and allies). Heliamphora is limited to South America, but the family contains two other genera, Sarracenia and Darlingtonia, which are endemic to the Southeastern United States (with the exception of one species) and California respectively. Sarracenia purpurea subsp. purpurea (the northern pitcher plant) can be found as far north as Canada. Sarracenia is the pitcher plant genus most commonly encountered in cultivation, because it is relatively hardy and easy to grow.

In the genus Sarracenia, the problem of pitcher overflow is solved by an operculum, which is essentially a flared leaflet that covers the opening of the rolled-leaf tube and protects it from rain. Possibly because of this improved waterproofing, Sarracenia species secrete enzymes such as proteases and phosphatases into the digestive fluid at the bottom of the pitcher Heliamphora relies on bacterial digestion alone. The enzymes digest the proteins and nucleic acids in the prey, releasing amino acids and phosphate ions, which the plant absorbs. In at least one species, Sarracenia flava, the nectar bribe is laced with coniine, a toxic alkaloid also found in hemlock, which probably increases the efficiency of the traps by intoxicating prey. [18]

Darlingtonia californica, the cobra plant, possesses an adaptation also found in Sarracenia psittacina and, to a lesser extent, in Sarracenia minor: the operculum is balloon-like and almost seals the opening to the tube. This balloon-like chamber is pitted with areolae, chlorophyll-free patches through which light can penetrate. Insects, mostly ants, enter the chamber via the opening underneath the balloon. Once inside, they tire themselves trying to escape from these false exits, until they eventually fall into the tube. Prey access is increased by the "fish tails", outgrowths of the operculum that give the plant its name. Some seedling Sarracenia species also have long, overhanging opercular outgrowths Darlingtonia may therefore represent an example of neoteny.

The second major group of pitcher plants are the monkey cups or tropical pitcher plants of the genus Nepenthes. In the hundred or so species of this genus, the pitcher is borne at the end of a tendril, which grows as an extension to the midrib of the leaf. Most species catch insects, although the larger ones, such as Nepenthes rajah, also occasionally take small mammals and reptiles. Nepenthes bicalcarata possesses two sharp thorns that project from the base of the operculum over the entrance to the pitcher. These likely serve to lure insects into a precarious position over the pitcher mouth, where they may lose their footing and fall into the fluid within. [19]

The pitfall trap has evolved independently in at least two other groups. The Albany pitcher plant Cephalotus follicularis is a small pitcher plant from Western Australia, with moccasin-like pitchers. The rim of its pitcher's opening (the peristome) is particularly pronounced (both secrete nectar) and provides a thorny overhang to the opening, preventing trapped insects from climbing out.

The final carnivore with a pitfall-like trap is the bromeliad Brocchinia reducta. Like most relatives of the pineapple, the tightly packed, waxy leaf bases of the strap-like leaves of this species form an urn. In most bromeliads, water collects readily in this urn and may provide habitats for frogs, insects and, more useful for the plant, diazotrophic (nitrogen-fixing) bacteria. In Brocchinia, the urn is a specialised insect trap, with a loose, waxy lining and a population of digestive bacteria. [ citation needed ]

Flypaper traps Edit

The flypaper trap utilises sticky mucilage or glue. The leaf of flypaper traps is studded with mucilage-secreting glands, which may be short (like those of the butterworts), or long and mobile (like those of many sundews). Flypapers have evolved independently at least five times. There is evidence that some clades of flypaper traps have evolved from morphologically more complex traps such as pitchers. [9]

In the genus Pinguicula, the mucilage glands are quite short (sessile), and the leaf, while shiny (giving the genus its common name of 'butterwort'), does not appear carnivorous. However, this belies the fact that the leaf is an extremely effective trap of small flying insects (such as fungus gnats), and its surface responds to prey by relatively rapid growth. This thigmotropic growth may involve rolling of the leaf blade (to prevent rain from splashing the prey off the leaf surface) or dishing of the surface under the prey to form a shallow digestive pit.

The sundew genus (Drosera) consists of over 100 species of active flypapers whose mucilage glands are borne at the end of long tentacles, which frequently grow fast enough in response to prey (thigmotropism) to aid the trapping process. The tentacles of D. burmanii can bend 180° in a minute or so. Sundews are extremely cosmopolitan and are found on all the continents except the Antarctic mainland. They are most diverse in Australia, the home to the large subgroup of pygmy sundews such as D. pygmaea and to a number of tuberous sundews such as D. peltata, which form tubers that aestivate during the dry summer months. These species are so dependent on insect sources of nitrogen that they generally lack the enzyme nitrate reductase, which most plants require to assimilate soil-borne nitrate into organic forms. [ citation needed ]

Closely related to Drosera is the Portuguese dewy pine, Drosophyllum, which differs from the sundews in being passive. Its leaves are incapable of rapid movement or growth. Unrelated, but similar in habit, are the Australian rainbow plants (Byblis). Drosophyllum is unusual in that it grows under near-desert conditions almost all other carnivores are either bog plants or grow in moist tropical areas. Recent molecular data (particularly the production of plumbagin) indicate that the remaining flypaper, Triphyophyllum peltatum, a member of the Dioncophyllaceae, is closely related to Drosophyllum and forms part of a larger clade of carnivorous and non-carnivorous plants with the Droseraceae, Nepenthaceae, Ancistrocladaceae and Plumbaginaceae. This plant is usually encountered as a liana, but in its juvenile phase, the plant is carnivorous. This may be related to a requirement for specific nutrients for flowering.

Snap traps Edit

The only two active snap traps—the Venus flytrap (Dionaea muscipula) and the waterwheel plant (Aldrovanda vesiculosa)—had a common ancestor with the snap trap adaptation, which had evolved from an ancestral lineage that utilised flypaper traps. [20] Their trapping mechanism has also been described as a "mouse trap", "bear trap" or "man trap", based on their shape and rapid movement. However, the term snap trap is preferred as other designations are misleading, particularly with respect to the intended prey. Aldrovanda is aquatic and specialised in catching small invertebrates Dionaea is terrestrial and catches a variety of arthropods, including spiders. [21]

The traps are very similar, with leaves whose terminal section is divided into two lobes, hinged along the midrib. Trigger hairs (three on each lobe in Dionaea muscipula, many more in the case of Aldrovanda) inside the trap lobes are sensitive to touch. When a trigger hair is bent, stretch-gated ion channels in the membranes of cells at the base of the trigger hair open, generating an action potential that propagates to cells in the midrib. [22] These cells respond by pumping out ions, which may either cause water to follow by osmosis (collapsing the cells in the midrib) or cause rapid acid growth. [23] The mechanism is still debated, but in any case, changes in the shape of cells in the midrib allow the lobes, held under tension, to snap shut, [22] flipping rapidly from convex to concave [24] and interring the prey. This whole process takes less than a second. In the Venus flytrap, closure in response to raindrops and blown-in debris is prevented by the leaves having a simple memory: for the lobes to shut, two stimuli are required, 0.5 to 30 seconds apart. [25] [26]

The snapping of the leaves is a case of thigmonasty (undirected movement in response to touch). Further stimulation of the lobe's internal surfaces by the struggling insects causes the lobes to close even tighter (thigmotropism), sealing the lobes hermetically and forming a stomach in which digestion occurs over a period of one to two weeks. Leaves can be reused three or four times before they become unresponsive to stimulation, depending on the growing conditions.

Bladder traps Edit

Bladder traps are exclusive to the genus Utricularia, or bladderworts. The bladders (vesiculae) pump ions out of their interiors. Water follows by osmosis, generating a partial vacuum inside the bladder. The bladder has a small opening, sealed by a hinged door. In aquatic species, the door has a pair of long trigger hairs. Aquatic invertebrates such as Daphnia touch these hairs and deform the door by lever action, releasing the vacuum. The invertebrate is sucked into the bladder, where it is digested. Many species of Utricularia (such as U. sandersonii) are terrestrial, growing in waterlogged soil, and their trapping mechanism is triggered in a slightly different manner. Bladderworts lack roots, but terrestrial species have anchoring stems that resemble roots. Temperate aquatic bladderworts generally die back to a resting turion during the winter months, and U. macrorhiza appears to regulate the number of bladders it bears in response to the prevailing nutrient content of its habitat. [17]

Lobster-pot traps Edit

A lobster-pot trap is a chamber that is easy to enter, and whose exit is either difficult to find or obstructed by inward-pointing bristles. Lobster pots are the trapping mechanism in Genlisea, the corkscrew plants. These plants appear to specialise in aquatic protozoa. A Y-shaped modified leaf allows prey to enter but not exit. Inward-pointing hairs force the prey to move in a particular direction. Prey entering the spiral entrance that coils around the upper two arms of the Y are forced to move inexorably towards a stomach in the lower arm of the Y, where they are digested. Prey movement is also thought to be encouraged by water movement through the trap, produced in a similar way to the vacuum in bladder traps, and probably evolutionarily related to it.

Outside of Genlisea, features reminiscent of lobster-pot traps can be seen in Sarracenia psittacina, Darlingtonia californica, and, some horticulturalists argue, Nepenthes aristolochioides.

Combination traps Edit

The trapping mechanism of the sundew Drosera glanduligera combines features of both flypaper and snap traps it has been termed a catapult-flypaper trap. [27] However, this is not the only combination traps. Nepenthes jamban is a combination of pitfall and flypaper traps because it has a sticky pitcher fluid.

Most Sumatran nepenthes, like N. inermis also have this method. For example, N. Dubia and N. flava also use this method.

Borderline carnivores Edit

To be defined as carnivorous, a plant must first exhibit an adaptation of some trait specifically for the attraction, capture, or digestion of prey. Only one trait needs to have evolved that fits this adaptive requirement, as many current carnivorous plant genera lack some of the above-mentioned attributes. The second requirement is the ability to absorb nutrients from dead prey and gain a fitness advantage from the integration of these derived nutrients (mostly amino acids and ammonium ions) [28] either through increased growth or pollen and/or seed production. However, plants that may opportunistically utilise nutrients from dead animals without specifically seeking and capturing fauna are excluded from the carnivorous definition. The second requirement also differentiates carnivory from defensive plant characteristics that may kill or incapacitate insects without the advantage of nutrient absorption. Due to the observation that many currently classified carnivores lack digestive enzymes for breaking down nutrients and instead rely upon mutualistic and symbiotic relationships with bacteria, ants, or insect, this adaptation has been added to the carnivorous definition. [8] [29] Despite this, there are cases where plants appear carnivorous, in that they fulfill some of the above definition, but are not truly carnivorous. Some botanists argue that there is a spectrum of carnivory found in plants: from completely non-carnivorous plants like cabbages, to borderline carnivores, to unspecialised and simple traps, like Heliamphora, to extremely specialised and complex traps, like that of the Venus flytrap. [7]

A possible carnivore is the genus Roridula the plants in this genus produce sticky leaves with resin-tipped glands and look extremely similar to some of the larger sundews. However, they do not directly benefit from the insects they catch. Instead, they form a mutualistic symbiosis with species of assassin bug (genus Pameridea), which eat the trapped insects. The plant benefits from the nutrients in the bugs' feces. [30] By some definitions this would still constitute botanical carnivory. [7]

A number of species in the Martyniaceae (previously Pedaliaceae), such as Ibicella lutea, have sticky leaves that trap insects. However, these plants have not been shown conclusively to be carnivorous. [31] Likewise, the seeds of Shepherd's Purse, [31] urns of Paepalanthus bromelioides, [32] bracts of Passiflora foetida, [33] and flower stalks and sepals of triggerplants (Stylidium) [34] appear to trap and kill insects, but their classification as carnivores is contentious.

Charles Darwin concluded that carnivory in plants was convergent, writing in 1875 that carnivorous genera Utricularia and Nepenthes were not "at all related to the [carnivorous family] Droseraceae". [4] This remained a subject of debate for over a century. In 1960, Leon Croizat concluded that carnivory was monophyletic, and placed all the carnivorous plants together at the base of the angiosperms. [9] Molecular studies over the past 30 years have led to a wide consensus that Darwin was correct, with studies showing that carnivory evolved at least six times in the angiosperms, and that trap designs such as pitcher traps and flypaper traps are analogous rather than homologous. [8]

Researchers using molecular data have concluded that carnivory evolved independently in the Poales (Brocchinia and Catopsis in the Bromelaceae), the Caryophyllales (Droseraceae, Nepenthaceae, Drosophyllaceae, Dioncophyllaceae), the Oxalidales (Cephalotus), the Ericales (Sarraceniaceae and Roridulaceae), and twice in the Lamiales (Lentibulariaceae and independently in Byblidaceae). [9] The oldest evolution of an existing carnivory lineage has been dated to 85.6 million years ago, with the most recent being Brocchinia reducta in the Bromeliaceae estimated at only 1.9 mya. [35]

The evolution of carnivorous plants is obscured by the paucity of their fossil record. Very few fossils have been found, and then usually only as seed or pollen. Carnivorous plants are generally herbs, and their traps are produced by primary growth. They generally do not form readily fossilisable structures such as thick bark or wood.

Still, much can be deduced from the structure of current traps and their ecological interactions. It is widely believed that carnivory evolved as a method to increase nutrients in extremely nutrient poor conditions, leading to a cost-benefit model for botanical carnivory. Cost-benefit models are given under the assumption that there is a set amount of energy potentially available for an organism, which leads to trade-offs when energy is allocated to certain functions to maximise competitive ability and fitness. For carnivory, the trait could only evolve if the increase in nutrients from prey capture exceeded the cost of investment in carnivorous adaptations. [29]

Most carnivorous plants live in habitats with high light, waterlogged soils, and extremely low soil nitrogen and phosphorus, producing the ecological impetus to derive nitrogen from an alternate source. High light environments allowed for the trade off between photosynthetic leaves and prey capturing traps that are photosynthetically inefficient. To compensate for photosynthetically inefficient material, the nutrients obtained through carnivory would need to increase photosynthesis by investing in more leaf mass, i.e. growing. This means when there is a shortage of nutrients and enough light and water, prey capture and digestion has the greatest impact on photosynthetic gains, favoring the evolution of plant adaptations which allowed for more effective and efficient carnivory. [7] [28] Due to the large amount of energy and resources allocated to carnivorous adaptations. i.e. the production of lures, digestive enzymes, modified leaf structures, and the decreased rate of photosynthesis over total leaf area, some authors argue that carnivory is an evolutionary last resort when nitrogen and phosphorus are limited in an ecosystem. [36]

Pitfall traps are derived from rolled leaves, which evolved several independent times through convergent evolution. The vascular tissues of Sarracenia is a case in point. The keel along the front of the trap contains a mixture of leftward- and rightward-facing vascular bundles, as would be predicted from the fusion of the edges of an adaxial (stem-facing) leaf surface. Flypapers also show a simple evolutionary gradient from sticky, non-carnivorous leaves, through passive flypapers to active forms. Molecular data show the DionaeaAldrovanda clade is closely related to Drosera, [37] and evolved from active flypaper traps into snap traps. [20]

It has been suggested that all trap types are modifications of a similar basic structure—the hairy leaf. [38] Hairy (or more specifically, stalked-glandular) leaves can catch and retain drops of rainwater, especially if shield-shaped or peltate, thus promoting bacteria growth. Insects land on the leaf, become mired by the surface tension of the water, and suffocate. Bacteria jumpstart decay, releasing from the corpse nutrients that the plant can absorb through its leaves. This foliar feeding can be observed in most non-carnivorous plants. Plants that were better at retaining insects or water therefore had a selective advantage. Rainwater can be retained by cupping the leaf, and pitfall traps may have evolved simply by selection pressure for the production of more deeply cupped leaves, followed by "zipping up" of the margins and subsequent loss of most of the hairs. Alternatively, insects can be retained by making the leaf stickier by the production of mucilage, leading to flypaper traps.

The lobster-pot traps of Genlisea are difficult to interpret. They may have developed from bifurcated pitchers that later specialised on ground-dwelling prey or, perhaps, the prey-guiding protrusions of bladder traps became more substantial than the net-like funnel found in most aquatic bladderworts. Whatever their origin, the helical shape of the lobster pot is an adaptation that displays as much trapping surface as possible in all directions when buried in moss.

The traps of the bladderworts may have derived from pitchers that specialised in aquatic prey when flooded, like Sarracenia psittacina does today. Escaping prey in terrestrial pitchers have to climb or fly out of a trap, and both of these can be prevented by wax, gravity and narrow tubes. However, a flooded trap can be swum out of, so in Utricularia, a one-way lid may have developed to form the door of a proto-bladder. Later, this may have become active by the evolution of a partial vacuum inside the bladder, tripped by prey brushing against trigger hairs on the door of the bladder.

The active glue traps use rapid plant movements to trap their prey. Rapid plant movement can result from actual growth, or from rapid changes in cell turgor, which allow cells to expand or contract by quickly altering their water content. Slow-moving flypapers like Pinguicula exploit growth, while the Venus flytrap uses such rapid turgor changes which make glue unnecessary. The stalked glands that once made glue became teeth and trigger hairs in species with active snap traps —an example of natural selection hijacking preexisting structures for new functions. [20]

Recent taxonomic analysis [39] of the relationships within the Caryophyllales indicate that the Droseraceae, Triphyophyllum, Nepenthaceae and Drosophyllum, while closely related, are embedded within a larger clade that includes non-carnivorous groups such as the tamarisks, Ancistrocladaceae, Polygonaceae and Plumbaginaceae. The tamarisks possess specialised salt-excreting glands on their leaves, as do several of the Plumbaginaceae (such as the sea lavender, Limonium), which may have been co-opted for the excretion of other chemicals, such as proteases and mucilage. Some of the Plumbaginaceae (e.g. Ceratostigma) also have stalked, vascularised glands that secrete mucilage on their calyces and aid in seed dispersal and possibly in protecting the flowers from crawling parasitic insects. The balsams (such as Impatiens), which are closely related to the Sarraceniaceae and Roridula, similarly possess stalked glands.

Philcoxia is unique in the Plantaginaceae as a result of its subterranean stems and leaves, which have been shown to be used in the capture of nematodes. These plants grow in sand in Brazil, where they are likely to receive other nutrients. Like many other types of carnivorous plant, stalked glands are seen on the leaves. Enzymes on the leaves are used to digest the worms and release their nutrients. [40]

The only traps that are unlikely to have descended from a hairy leaf or sepal are the carnivorous bromeliads (Brocchinia and Catopsis). These plants use the urn—a fundamental part of a bromeliad—for a new purpose and build on it by the production of wax and the other paraphernalia of carnivory.

Botanical carnivory has evolved in several independent families peppered throughout the angiosperm phylogeny, showing that carnivorous traits underwent convergent evolution multiple times to create similar morphologies across disparate families. Results of genetic testing published in 2017 found an example of convergent evolution - a digestive enzyme with the same functional mutations across unrelated lineages. [41]

Carnivorous plants are widespread but rather rare. They are almost entirely restricted to habitats such as bogs, where soil nutrients are extremely limiting, but where sunlight and water are readily available. Only under such extreme conditions is carnivory favored to an extent that makes the adaptations advantageous.

The archetypal carnivore, the Venus flytrap, grows in soils with almost immeasurable nitrate and calcium levels. Plants need nitrogen for protein synthesis, calcium for cell wall stiffening, phosphate for nucleic acid synthesis, and iron and magnesium for chlorophyll synthesis. The soil is often waterlogged, which favours the production of toxic ions such as ammonium, and its pH is an acidic 4 to 5. Ammonium can be used as a source of nitrogen by plants, but its high toxicity means that concentrations high enough to fertilise are also high enough to cause damage.

However, the habitat is warm, sunny, constantly moist, and the plant experiences relatively little competition from low growing Sphagnum moss. Still, carnivores are also found in very atypical habitats. Drosophyllum lusitanicum is found around desert edges and Pinguicula valisneriifolia on limestone (calcium-rich) cliffs. [42]

In all the studied cases, carnivory allows plants to grow and reproduce using animals as a source of nitrogen, phosphorus and possibly potassium. [43] [44] [45] However, there is a spectrum of dependency on animal prey. Pygmy sundews are unable to use nitrate from soil because they lack the necessary enzymes (nitrate reductase in particular). [46] Common butterworts (Pinguicula vulgaris) can use inorganic sources of nitrogen better than organic sources, but a mixture of both is preferred. [43] European bladderworts seem to use both sources equally well. Animal prey makes up for differing deficiencies in soil nutrients.

Plants use their leaves to intercept sunlight. The energy is used to reduce carbon dioxide from the air with electrons from water to make sugars (and other biomass) and a waste product, oxygen, in the process of photosynthesis. Leaves also respire, in a similar way to animals, by burning their biomass to generate chemical energy. This energy is temporarily stored in the form of ATP (adenosine triphosphate), which acts as an energy currency for metabolism in all living things. As a waste product, respiration produces carbon dioxide.

For a plant to grow, it must photosynthesise more than it respires. Otherwise, it will eventually exhaust its biomass and die. The potential for plant growth is net photosynthesis, the total gross gain of biomass by photosynthesis, minus the biomass lost by respiration. Understanding carnivory requires a cost-benefit analysis of these factors. [28]

In carnivorous plants, the leaf is not just used to photosynthesise, but also as a trap. Changing the leaf shape to make it a better trap generally makes it less efficient at photosynthesis. For example, pitchers have to be held upright, so that only their opercula directly intercept light. The plant also has to expend extra energy on non-photosynthetic structures like glands, hairs, glue and digestive enzymes. [47] To produce such structures, the plant requires ATP and respires more of its biomass. Hence, a carnivorous plant will have both decreased photosynthesis and increased respiration, making the potential for growth small and the cost of carnivory high.

Being carnivorous allows the plant to grow better when the soil contains little nitrate or phosphate. In particular, an increased supply of nitrogen and phosphorus makes photosynthesis more efficient, because photosynthesis depends on the plant being able to synthesise very large amounts of the nitrogen-rich enzyme RuBisCO (ribulose-1,5-bis-phosphate carboxylase/oxygenase), the most abundant protein on Earth.

It is intuitively clear that the Venus flytrap is more carnivorous than Triphyophyllum peltatum. The former is a full-time moving snap-trap the latter is a part-time, non-moving flypaper. The energy "wasted" by the plant in building and fuelling its trap is a suitable measure of the carnivory of the trap.

Using this measure of investment in carnivory, a model can be proposed. [28] Above is a graph of carbon dioxide uptake (potential for growth) against trap respiration (investment in carnivory) for a leaf in a sunny habitat containing no soil nutrients at all. Respiration is a straight line sloping down under the horizontal axis (respiration produces carbon dioxide). Gross photosynthesis is a curved line above the horizontal axis: as investment increases, so too does the photosynthesis of the trap, as the leaf receives a better supply of nitrogen and phosphorus. Eventually another factor (such as light intensity or carbon dioxide concentration) will become more limiting to photosynthesis than nitrogen or phosphorus supply. As a result, increasing the investment will not make the plant grow better. The net uptake of carbon dioxide, and therefore, the plant's potential for growth, must be positive for the plant to survive. There is a broad span of investment where this is the case, and there is also a non-zero optimum. Plants investing more or less than this optimum will take up less carbon dioxide than an optimal plant, and hence growing less well. These plants will be at a selective disadvantage. At zero investment the growth is zero, because a non-carnivorous plant cannot survive in a habitat with absolutely no soil-borne nutrients. Such habitats do not exist, so for example, Sphagnum absorbs the tiny amounts of nitrates and phosphates in rain very efficiently and also forms symbioses with diazotrophic cyanobacteria.

In a habitat with abundant soil nutrients but little light (as shown above), the gross photosynthesis curve will be lower and flatter, because light will be more limiting than nutrients. A plant can grow at zero investment in carnivory this is also the optimum investment for a plant, as any investment in traps reduces net photosynthesis (growth) to less than the net photosynthesis of a plant that obtains its nutrients from soil alone.

Carnivorous plants exist between these two extremes: the less limiting light and water are, and the more limiting soil nutrients are, the higher the optimum investment in carnivory, and hence the more obvious the adaptations will be to the casual observer.

The most obvious evidence for this model is that carnivorous plants tend to grow in habitats where water and light are abundant and where competition is relatively low: the typical bog. Those that do not tend to be even more fastidious in some other way. Drosophyllum lusitanicum grows where there is little water, but it is even more extreme in its requirement for bright light and low disturbance than most other carnivores. Pinguicula valisneriifolia grows in soils with high levels of calcium but requires strong illumination and lower competition than many butterworts. [48]

In general, carnivorous plants are poor competitors, because they invest too heavily in structures that have no selective advantage in nutrient-rich habitats. They succeed only where other plants fail. Carnivores are to nutrients what cacti are to water. Carnivory only pays off when the nutrient stress is high and where light is abundant. [49] When these conditions are not met, some plants give up carnivory temporarily. Sarracenia spp. produce flat, non-carnivorous leaves (phyllodes) in winter. Light levels are lower than in summer, so light is more limiting than nutrients, and carnivory does not pay. The lack of insects in winter exacerbates the problem. Damage to growing pitcher leaves prevents them from forming proper pitchers, and again, the plant produces a phyllode instead.

Many other carnivores shut down in some seasons. Tuberous sundews die back to tubers in the dry season, bladderworts to turions in winter, and non-carnivorous leaves are made by most butterworts and Cephalotus in the less favourable seasons. Utricularia macrorhiza varies the number of bladders it produces based on the expected density of prey. [50] Part-time carnivory in Triphyophyllum peltatum may be due to an unusually high need for potassium at a certain point in the life cycle, just before flowering.

The more carnivorous a plant is, the less conventional its habitat is likely to be. Venus flytraps live in a very specialised habitat, whereas less carnivorous plants (Byblis, Pinguicula) are found in less unusual habitats (i.e., those typical for non-carnivores). Byblis and Drosophyllum both come from relatively arid regions and are both passive flypapers, arguably the lowest maintenance form of trap. Venus flytraps filter their prey using the teeth around the trap's edge, so as not to waste energy on hard-to-digest prey. In evolution, laziness pays, because energy can be used for reproduction, and short-term benefits in reproduction will outweigh long-term benefits in anything else.

Carnivory rarely pays, so even carnivorous plants avoid it when there is too little light or an easier source of nutrients, and they use as few carnivorous features as are required at a given time or for a given prey item. There are very few habitats stressful enough to make investing biomass and energy in trigger hairs and enzymes worthwhile. Many plants occasionally benefit from animal protein rotting on their leaves, but carnivory that is obvious enough for the casual observer to notice is rare. [51]

Bromeliads seem very well preadapted to carnivory, but only one or two species can be classified as truly carnivorous. By their very shape, bromeliads will benefit from increased prey-derived nutrient input. In this sense, bromeliads are probably carnivorous, but their habitats are too dark for more extreme, recognisable carnivory to evolve. Most bromeliads are epiphytes, and most epiphytes grow in partial shade on tree branches. Brocchinia reducta, on the other hand, is a ground dweller.

Many carnivorous plants are not strongly competitive and rely on circumstances to suppress dominating vegetation. Accordingly, some of them rely on fire ecology for their continued survival.

For the most part carnivorous plant populations are not dominant enough to be dramatically significant, ecologically speaking, but there is an impressive variety of organisms that interact with various carnivorous plants in sundry relationships of kleptoparasitism, commensalism, and mutualism. For example, small insectivores such as tree frogs often exploit the supply of prey to be found in pitcher plants, and the frog Microhyla nepenthicola actually specialises in such habitats. Certain crab spiders such as Misumenops nepenthicola live largely on the prey of Nepenthes, and other, less specialised, spiders may build webs where they trap insects attracted by the smell or appearance of the traps some scavengers, detritivores, and also organisms that harvest or exploit those in turn, such as the mosquito Wyeomyia smithii are largely or totally dependent on particular carnivorous plants. Plants such as Roridula species combine with specialised bugs (Pameridea roridulae) in benefiting from insects trapped on their leaves.

Associations with species of pitcher plants are so many and varied that the study of Nepenthes infauna is something of a discipline in its own right. Camponotus schmitzi, the diving ant, has an intimate degree of mutualism with the pitcher plant Nepenthes bicalcarata it not only retrieves prey and detritus from beneath the surface of the liquid in the pitchers, but repels herbivores, and cleans the pitcher peristome, maintaining its slippery nature. The ants have been reported to attack struggling prey, hindering their escape, so there might be an element of myrmecotrophy to the relationship. Numerous species of mosquitoes lay their eggs in the liquid, where their larvae play various roles, depending on species some eat microbes and detritus, as is common among mosquito larvae, whereas some species of Toxorhynchites also breed in pitchers, and their larvae are predators of other species of mosquito larvae. Apart from the crab spiders on pitchers, an actual small, red crab Geosesarma malayanum will enter the fluid, robbing and scavenging, though reputedly it does so at some risk of being captured and digested itself. [51]

Nepenthes rajah has a remarkable mutualism with two unrelated small mammals, the mountain treeshrew (Tupaia montana) and the summit rat (Rattus baluensis). The tree shrews and the rats defecate into the plant's traps while visiting them to feed on sweet, fruity secretions from glands on the pitcher lids. [52] The tree shrew also has a similar relationship with at least two other giant species of Nepenthes. More subtly, Hardwicke's woolly bat (Kerivoula hardwickii), a small species, roosts beneath the operculum (lid) of Nepenthes hemsleyana. [53] The bat's excretions that land in the pitcher pay for the shelter, as it were. To the plant the excreta are more readily assimilable than intact insects would be.

There also is a considerable list of Nepenthes endophytes these are microbes other than pathogens that live in the tissues of pitcher plants, often apparently harmlessly.

Another important area of symbiosis between carnivorous plants and insects is pollination. While many species of carnivorous plant can reproduce asexually via self-pollination or vegetative propagation, many carnivorous plants are insect-pollinated. [54] Outcross pollination is beneficial as it increases genetic diversity. This means that carnivorous plants undergo an evolutionary and ecological conflict often called the pollinator-prey conflict. [54] There are several ways by which carnivorous plants reduce the strain of the pollinator-prey conflict. For long-lived plants, the short-term loss of reproduction may be offset by the future growth made possible by resources obtained from prey. [54] Other plants might "target" different species of insect for pollination and prey using different olfactory and visual cues. [54]

Approximately half of the plant species assessed by the IUCN are considered threatened (vulnerable, endangered or critically endangered). Common threats are habitat loss as a result of agriculture, collection of wild plants, pollution, invasive species, residential and commercial development, energy production, mining, transportation services, geologic events, climate change, severe weather, and many other anthropogenic activities. [55] Species in the same genus were proven to face similar threats. Threat by continent is deemed highly variable, with threats found for 19 species in North America, 15 species in Asia, seven species in Europe, six species in South America, two species in Africa, and one species in Australia Indicator species' such as Sarracenia reveal positive associations with regard to these threats. Certain threats are also positively correlated themselves, with residential and commercial development, natural systems modifications, invasive species, and pollution having positive associations. Conservation research is aiming to further quantify the effects of threats, such as pollution, on carnivorous plants, as well as to quantify the extinction risks. Only 17% of species had been assessed as of 2011, according to the IUCN. [56] Carnivorous plant conservation will help maintain important ecosystems and prevent secondary extinctions of specialist species that rely on them [11] such as foundation species which may seek refuge or rely on certain plants for their existence. Research suggests a holistic approach, targeted at the habitat-level of carnivorous plants, may be required for successful conservation. [57]

The classification of all flowering plants is currently in a state of flux. In the Cronquist system, the Droseraceae and Nepenthaceae were placed in the order Nepenthales, based on the radial symmetry of their flowers and their possession of insect traps. The Sarraceniaceae was placed either in the Nepenthales, or in its own order, the Sarraceniales. The Byblidaceae, Cephalotaceae, and Roridulaceae were placed in the Saxifragales and the Lentibulariaceae in the Scrophulariales (now subsumed into the Lamiales [58] ).

In more modern classification, such as that of the Angiosperm Phylogeny Group, the families have been retained, but they have been redistributed amongst several disparate orders. It is also recommended that Drosophyllum be considered in a monotypic family outside the rest of the Droseraceae, probably more closely allied to the Dioncophyllaceae. The current recommendations are shown below (only carnivorous genera are listed):


Araujia Species, Bladder Vine, Cruel Plant, Moth Plant, Poor Man's Stephanotis, White Bladderflower

Family: Apocynaceae (a-pos-ih-NAY-see-ee) (Info)
Genus: Araujia (ar-RAW-jee-uh) (Info)
Species: sericifera (ser-ik-IF-er-uh) (Info)
Synonym:Araujia albens
Synonym:Araujia calycina
Synonym:Araujia hortorum
Synonym:Araujia undulata

Category:

Water Requirements:

Average Water Needs Water regularly do not overwater

Sun Exposure:

Foliage:

Foliage Color:

Height:

Spacing:

Hardiness:

USDA Zone 10a: to -1.1 °C (30 °F)

USDA Zone 10b: to 1.7 °C (35 °F)

USDA Zone 11: above 4.5 °C (40 °F)

Where to Grow:

Suitable for growing in containers

Danger:

Handling plant may cause skin irritation or allergic reaction

Bloom Color:

Bloom Characteristics:

Bloom Size:

Bloom Time:

Other details:

May be a noxious weed or invasive

Soil pH requirements:

Patent Information:

Propagation Methods:

From seed sow indoors before last frost

Seed Collecting:

Allow pods to dry on plant break open to collect seeds

Regional

This plant is said to grow outdoors in the following regions:

Beulaville, North Carolina

Johns Island, South Carolina

Gardeners' Notes:

On Apr 28, 2011, StonoRiver from Johns Island, SC wrote:

I've found this plant to be completely manageable in zone 8A, but in warmer climes I can see where it might be a problem. It stops flowering/growing here in November/December, so it never forms seed pods. Will die to the ground in bad winter years, but comes back reliably from the roots every time, and grows rapidly back to almost it's original size in a few months. Mine grows in light shade.

On Oct 19, 2010, johnthelandlord from Los Angeles, CA wrote:

It took me a while to figure what this was out, it started growing in a section of my apt buildings courtyard. At first it just had the flowers, now it has these large funky fruits on it. It seems to grow very fast and likes to spin around and choke the other plants around it.

It seems to be popping up all over this one area..lots of new shoots everywhere.

I am considering putting an end to it. Also, its EXTREMELY hard to break the vines buy trying to pull them off. This stuff is like nylon!

On Sep 8, 2010, Xeramtheum from Summerville, SC (Zone 8a) wrote:

For me in zone 8a this is an aphid and ant magnet.

On Apr 11, 2010, nomosno from San Diego, CA (Zone 10b) wrote:

I've had a horrible experience with this plant! I understand perfectly why it is called Cruel Plant. I picked up a seed pod from the Wild Animal Park in San Diego and planted the seeds. It sprouted easily and I planted the seedlings next to a trellis that I hoped this plant would grow onto. And grow it did, within a year it fully covered it and by the next year it started to produce seed pods. The pods, when ripe, open up and release hundreds of flying seeds into the air, with dozens of seed pods you begin to get inundated with seedlings everywhere. Trying to control the plant by cutting it back is hampered by the fact that it releases a copious amount of corrosive white sticky sap from every cut surface, which gets into your tools, and onto your body. Try to do this with the vines growing. read more overhead on the trellis! You practically have to wear protective clothing to deal with this monster. I finally destroyed it about a year ago in a heroic battle, I still wage fights against the seedlings that pop up everywhere. This plant is not for a typical backyard in climates where it survives outside.

On Oct 27, 2009, fixpix from Weston-super-Mare,
United Kingdom wrote:

just here to say one of the pics is in fact another plant. i think it's the 5th from top.
a stephanotis.
i could be wrong, but doubt it.
haven't got this plant (araujia) but got seeds and will give it a try.
CALIN

On Jun 7, 2007, seedpicker_TX from (Taylor) Plano, TX (Zone 8a) wrote:

This vine is evergreen for me in zone 8a. It may lose some leaves in January and February, but never is completely defoliated.
It resembles a milkweed vine, and will ooze white milky sap, if a stem is crushed, cut or broken.
Moths of all types are attracted to the white flowers which are more fragrant at night.
The flowers trap the moth by the tongue, and later release the moth, although they frequently fail to release the moth, causing its death. thus the name "cruel vine''.
Very pretty flowers and easy to grow, although considered a noxious weed in some states. I tend to this vine every morning during bloom season, to save little captors.
It begins blooming for me late May, and will continue until Fall.

Vigorous, evergreen climber from South America

Has lance shaped, pale-mid green leaves with soft hairs beneath. Bears white or pale pink, bell shaped, scented flowers with a sticky pollen.

Likes a well drained, fertile soil in sun or partial shade. Grow indoors or at least bring them indoors when frost is expected.

Don't water too heavily in winter.

The flower scent attracts pollinators, especially moths. The pollen can trap the nectar seekers but will release the insect by the following morning, earning this plant it's common name.

Can become invasive in warmer regions of California and similar climes.

Incredibly easy from seed and fast growing.


Bladderpod Plant Care

Growing bladderpod flowers is easy if you are in a warm enough zone. In fact, bladderpod plant info indicates that these desert dwellers prefer neglect. Of course, this is only once they have been established, but the plant doesn’t need supplemental fertilizer or much extra water.

Spring rains are usually sufficient to establish seedlings but a small amount of water in the hottest parts of summer will be appreciated. Keep competitive weeds away from the root zone of plants.

As an addition to the landscape, bladderpod will provide food for many birds, especially quail. The plant is also fire resistant and has no known disease problems.


How to Grow an American Bladdernut

If you want to start growing an American bladdernut tree, you’ll need to live in a fairly cool climate. According to American bladdernut information, it thrives in U.S. Department of Agriculture plant hardiness zones 4 through 7.

One reason to grow these trees is the ease of American bladdernut care. Like most native plants, American bladdernut is very undemanding. It grows in almost any soil, including moist, wet and well-drained, and also tolerates alkaline soil.

Don’t worry too much about the site. You can plant the seedling in a full sun site, a partial shade site or a full shade site. In any setting, its required care is minimal.


Araujia sericifera * Bladder Vine

Araujia sericifera is a vine in the Milkweed Family, Asclepidacea. This family has been combined with the Apocynacea, the Dogbane Family. Araujia sericifera is native to South America. The Bladder Vine grows in full sun to complete shade. Once established the plants will need little or no water. Fragrant Creamy White to Pink flowers are moth pollinated from late Spring through to Fall. This plant can be a pest but it has some redeeming aspects. It turns out the Monarch Butterfly Caterpillars love to eat the leaves. This has proven quite useful. As to the cautionary side, the Bladder Vine is easily germinated from seed that floats away on a breeze. Araujia sericifera blooms for a long period of time, meaning there will be nearby seedlings for much of the season. Araujia sericifera likes to climb things, anything up to the tops of the trees or nearby fences and shrubs. They will wrap and even strangle trees and shrubs. But hey the monarchs eat them so they have come a ways back to being on my good plant list. Another bit of good news for the Monarch's the protazoan that is dangerous for them with the tropical milkweeds is not a problem due to the tenderness to even a mild frost. The tops will die back with any significant frost but these milkweed plants are potentially root hardy into the teens

Flowers and foliage of Araujia sericifera the Bladder Vine. High resolution photos are part of our garden image collection.

A feeding brick for the Monarch Butterfly Caterpillars, they are feeding on Bladder Vine, Araujia sercifera. The Milkweed related Bladder Vine is acceptable food for the Caterpillars, though the Monarch Butterflies will not lay their eggs on this plant. They were slow to think that this would be OK until the Narrow Leaf Milkweed plant started to get pretty bare. Then at every instar level they ate the Bladder Vine with the same enthusiasm as the Tropical Milkweed plants I stuck in next. I have started propagating both the Bladder Vine and the Tropical Milkweeds from the striped bare stems that the caterpillars left me. The brick was meant to hold down the Butterfly house at first but then with the aid of a masonry bit the brick became a vase holder for the milkweed leaves and stems of plants from the garden.

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