Outer and inner membranes: protective coverings that keep chloroplast structures enclosed.

Stroma: dense fluid within the chloroplast. Site of conversion of carbon dioxide to sugar.

Thylakoid: flattened sac-like membrane structures. Site of conversion of light energy to chemical energy.

Grana: dense layered stacks of thylakoid sacs. Sites of conversion of light energy to chemical energy.

Chlorophyll: a green pigment within the chloroplast. Absorbs light energy.

Introduction Rosary pea has been widely used in Florida as an ornamental plant for many years. The native range of rosary pea is India and parts of Asia, where this plant is used for various purposes. The roots of this plant are used to induce abortion and relieve abdominal discomfort. The seeds of this plant are so uniform in size and weight that they are used as standards in weight measurement. The seeds can also be used to make jewelry. Interestingly, one of the most deadly plant toxins, abrin, is produced by rosary pea (Abrus precatorius). Studies have shown that as little as 0.00015% of toxin per body weight will cause fatality in humans (a single seed). Interestingly, birds appear to be unaffected by the deadly toxin as they have been shown to readily disperse rosary pea seed.

Rosary pea is a small, high climbing vine with alternately compound leaves, 2-5 inches long, with 5 to 15 pairs of oblong leaflets. A key characteristic in identifying rosary pea is the lack of a terminal leaflet on the compound leaves. The flowers are small, pale, and violet to pink, clustered in leaf axils. The fruit is characteristic of a legume. The pod is oblong, flat and truncate shaped, roughly 1½ - 2 inches long. This seedpod curls back when it opens, revealing the seeds. The seeds are small, brilliant red with a black spot. These characteristics give the plant another common name of crab’s eyes.

Impacts

Rosary pea is found throughout central and southern Florida, including Marion, Lake, Palm Beach, and Manatee counties. All together, rosary pea has been collected from 27 counties throughout Florida. Undisturbed pinelands and hammocks are often invaded by Abrus. The Florida Exotic Pest Plant Council considers rosary pea a category 1 invasive species due to its ability to invade and displace native plant communities. Characteristic of a vining plant, rosary pea can grow over small trees and shrubs. Roots grow very deeply onto the ground and are very difficult to remove. Fire encourages the growth of Rosary pea.

Management

Preventative:

Regular monitoring and rouging of plants can prevent the spread and establishment of rosary pea. Programs to educate homeowners on proper plant identification will also reduce the spread of this species.

Cultural:

Native alternatives to rosary pea for use in home landscaping or natural areas include leather flower (Clematis crispa) or Carolina jessamine (Gelsemium sempervirens).

Mechanical:

Hand-pulling and removal of entire plants, particularly the roots, is practical for small infestations. Aggressive tillage is an option and very effective, but impractical in many areas. Fire provides only temporary control.

Biological:

There are no known biological agents for rosary pea.

Chemical:

Timing of application is critical to effectiveness; with applications in the fall prior to seed set being the most effective. Triclopyr is effective as a cut-stump treatment on large woody vines immediately after the vines are cut down. Triclopyr amine or glyphosate can be applied to the foliage at 3-5% or 1-3%, respectively.

The North American pitcher plants (Sarracenia) are divided into two groups: the northern pitcher plant (Sarracenia purpurea), in the northern United States and adjacent Canada, and the southeastern pitcher plants. Sarracenia alata is one of the southeastern pitcher plants, and can be found from eastern Texas to Mississippi. Here's a picture of it near Mobile, Alabama. At first glance, one only sees the pines, and pine forests in areas of white sand that stay wet in the summertime are habitats for most of the southeastern pitcher plants.

If you're looking for Sarracenia alata, you want to look for areas of pine forest. Not dense pine forest, but pine forest with meadow-like openings in it. These areas are waterlogged even in summertime because there are dense soils (clays, for example) underneath the white sand, so that water forms shallow pools or isn't far beneath the surface. These areas are acid--pines are good indicators of acid). And these boggy areas are poor in nutrients, notably nitrogen. The pitcher plants can get enough nitrogen from digesting insects to make up for the lack of nitrogen in the soil. Each tubular pitcher (leaf) contains a small pool of water, which contains insect-digesting chemicals (enzymes) at the bottom of the tube.

Here we see a flower and three leaves of Sarracenia alata. The leaf at left hasn't opened yet. The leaf in the middle is seen from the front. Notice the light green zone like a V at the mouth of the pitcher--that's where an insect lands and begins its exploration of the pitcher. It's looking for nectar droplets on the inside of the hood of the pitcher. Extending down from the V is a dark narrow fold that represents the margins of the leaf--as though they were sewn together like the seam in a cushion. The word "alata" in Latin means "winged," and this narrow wing on the front of the pitcher gives the plant its name. The leaf at the right is seen from the side, and we can see that the tip of the leaf forms a hood that overarches the mouth of the pitcher. The hood helps guide the insect to climb down into the tube, and it may also prevent rainwater from diluting the digestive fluid in the pitcher.

RAP TYPE: Pitfall Trap

A common plant in the bogs of the northeastern part of North America is Sarracenia purpurea (pitcher plant, Figure 1). Although its large leaves resemble tall pitchers partially filled with water, they are also good mimics of flowers, and it is the latter trait that fools both insects and humans. Although humans have nothing to fear if they try to smell the false flowers, flies easily become victims of the pitfall trap when they seek potential food inside. As the summer season progresses, the leaves become purplish red from the presence of anthocyanins, making them a lure to flies who are probably also attracted by the decaying amino acid odor of already trapped prey. Once the fly enters the hollow leaf, it confronts a waxy surface leading to a pool of water. Although a fly can often escape the surface of water, the pitcher plant reduces its chances by supplying a wetting agent that wets the fly's wings and prevents it from flying. Even if the fly succeeds in escaping the surface of the water, it is confronted by the steep sides of the leaf and, being unable to fly straight up like a helicopter, is forced to crash into the walls of the leaf. We have all seen flies climb the walls of our houses, but this leaf wall is somewhat more challenging.

The lower part of zone 3, (in Figure 3) is waxy and very slippery. The fly's feet soon slide like stepping onto a newly waxed floor in your sock feet. But if the fly does succeed in passing above that waxy zone, it is confronted with downward pointing hairs (Figure 4) in zone 1 (Figure 3), again preventing escape. Eventually the exhausted fly succumbs to the solution at the bottom of the leaf and the low pH slowly digests its tissues.

The plant seems to contribute little to the digestion process, but bacteria living in the pitcher provide digestive enzymes. Trapping of ants can be important to the digestion process as well. Along the outer edge of the leaf is a flat flange (Figure 5) that provides a trail of a sweet nectar-like substance leading to the opening of the pitcher. Ants often follow this trail and enter the pitcher, getting trapped in a manner similar to that of the fly.

Since ants are common in the Sphagnum hummocks of a bog, it is not too surprising that this plant is attractive to them. The abundant Sphagnum is certainly not one of their food plants. Once inside the pitcher (Figure 6), the ant dies and decays, thus releasing the formic acid made by the ant (formic acid results in the nasty stings some ants can cause). The formic acid contributes further to the digestive process, making the pH as low as 2.0. For Sarracenia in the southeastern United States, it appears that mineral nitrogen and phosphorus are not important limiting nutrients (Eleutarius & Jones 1969). However, when Christensen (1976) fed insects to one species, the concentrations of nitrogen and phosphorus in the leaf tissue was significantly higher than in controls. But pitcher plants are not only captors, they are also hosts to a variety of small organisms.

Several species of mosquito larvae complete their larval stage here, exiting to the surrounding moss to live out the pupal stage. A slightly larger inhabitant, the larva of the blowfly, Sarcophaga sarraceniae, spends its larval life deep at the bottom of the tube where it enjoys the decaying parts of the captive prey. When it matures to form the pupal stage, it likewise leaves the pitcher to pupate among the surrounding moss. But as an adult, it returns to the pitcher plant, this time to steal nectar from the flower and at the same time to pollinate it. Small organisms are not the only ones to inhabit these pitchers. Small frogs sit and wait in some species, taking advantage of the flies that are attracted by the odor.

The pitcher plant has not only unique leaves, but very strange flowers as well (Figure 7). Its petals are ordinary enough, with a deep burgundy color that attracts flies by looking like raw meat. But that is where its similarity to normal flowers seems to end. The sepals, usually green structures that protect the bud and then become inconspicuous when the flower opens, remain long after the petals fall off. In fact, the petals fall off quickly because they have very narrow attachments. The sepals are leathery and will even last through the snows of a northern winter! They usually become reddish themselves if they are exposed to direct sun (Figure 7).

The pistil, or female part of the flower, is the strangest part. It has a normal enough ovary that provides the enlarged base of the pistil, but the style expands into a large, star-shaped umbrella (Figure 8). This umbrella becomes the lowest part of the flower as it droops downward in its early open stages. As a result, the pollen that awaits in the anthers surrounding the ovary has a waiting landing platform. Soon the inside of the umbrella-shaped style is laden with pollen. And, the ovary drips nectar onto the platform as well.

When the blowfly approaches the flower, it first lands on one of the five points of the star, not suspecting that it has landed on the awaiting stigma that is ready to receive whatever pollen may have stuck to the body of the fly. From there, the fly descends onto the platform, where it crawls around gathering nectar, and inadvertently, pollen. When the fly tires of that flower, it will exit between the points, not across them, on its way to another flower.

Ca. 10 Listed Species
S. alata Wood (1863) | S. flava L. (1753) | S. jonesii Wherry (1929) | S. leucophylla Raf. (1817) | S. minor Walter (1788) | S. oreophila Wherry (1933) | S. purpurea L. (1753) | S. psittacina Michx. (1803) | S. rosea Naczi et al. (1999) | S. rubra Walter (1788)

Plants are eukaryotic organisms that are characterized by their ability to produce their own food. They are vital to all life on earth as they provide oxygen, shelter, clothing, food, and medicine for other living organisms.

Plants are very diverse and include organisms such as mosses, vines, trees, bushes, grasses, and ferns. Plants can be vascular or nonvascular, flowering or nonflowering, and seed bearing or non-seed bearing.

The information below describe the characteristics and parts of a flowering plant.

Parts of a Flowering Plant

Root System

Shoot System

• Sepal - green, leaf-like structure that protects the budding flower.
  
  
• Petal - colorful and often scented part of the flower that attracts insects.
  
  
• Stamen - the part of the flower that produces pollen. Consists of a filament and an anther.
  
  
  • Anther - sac located at the tip of the filament that contains pollen.
    
    
  • Filament - stalk that connects to and holds up the anther.
  
  
• Carpel - consists of the stigma, style, and ovary.
  
  
  • Stigma - the tip of the carpel that is sticky in order to collect pollen.
    
    
  • Style - the slender, neck-like portion of the carpel that leads to the ovary.
    
    
  • Ovary - structure at the base of the carpel that houses the ovule or egg.

Parts of a Flowering Plant: Summary

TRAP TYPE: Pitfall Trap
Currently 90 listed species occupying tropical habitats in Australia, Madagascar, Papua New Guinea, the Seychelles, Southeast Asia and Sri Lanka.

Nepenthes, a native of Southeast Asia and Australia, forms pitchers (cups) that hang from trees. Its pitcher is similar to that of the North American pitcher plant in that it relies on a pool of water to trap its prey. It has a most unusual leaf that first looks like a normal leaf, then develops a tendril at its tip, and finally the tip of the tendril develops an amazing pitcher. It gains support by twining the tendril around another plant. The trap, like our own pitcher plant, lures its prey into the pitfall trap by a combination of decaying odors and sometimes a red coloration. As the pitcher develops, it swells and droops due to its weight.

As it matures, it suddenly begins inflates with air. Once inflated it begins to fill with liquid, then opens, revealing the enticing interior. The top of the trap has a lid that initially covers the pitcher until growth is complete. When the leaf is fully grown, the lid opens and the trap is ready.

They attract insects with the odor of nectar. Once inside, the insect finds it cannot get a grip on the walls of the pitcher because a flaky wax on the interior surface peels off as it struggles to climb. Eventually, it falls into the water and struggles to escape. The motion caused by the struggle stimulates digestive glands to release a digestive acid. This acid is so strong that a midge will disappear within hours. The largest of these, the Rajah pitcher, is able to digest mice! Like our own pitcher plant, this one too has its live inhabitants, the largest of which is a small crab.

Insect larvae feed on the decaying remains of prey. Others live in the upper levels and dip down occasionally to seize one of the larval inhabitants. In one case, the plant provides a chamber in its stem where ants live. The ants venture to the pitchers, grab some of the decaying prey, and sit on the lip of the pitcher to dismember it. As they break apart the body, pieces fall back into the pitcher's awaiting pool, where the now smaller fragments decay more quickly than would a whole insect. As you can see, this page is being developed. There are currently 91 listed species of Nepenthes.

The master of sticky fly paper, Drosera (sundew), is a slow trap compared to the one in Venus Flytrap. However, the sundew relies on first trapping its prey with its sticky, glandular hairs, as shown in Figure 1, before it slowly rolls up the edges of the leaf. It does not fold like the Venus fly trap, but it can effective enclose small flies with the numerous hairs.

The sundews, so named because their glandular leaf hairs glisten like dew in the sun, are not only common in bogs, but can occur on sandy banks and other mineral soils poor in organic nitrogen and phosphorus. So fascinating is this tiny plant that Darwin (1875) spent 285 pages of his book on insectivorous plants describing his own experiments on it.

TRAP TYPE: Flypaper Trap
Currently Ca. 152 listed species occupying temperate and tropical habitats throughout the world.

The master of sticky fly paper, Drosera (sundew), is a slow trap compared to the one in Venus Flytrap. However, the sundew relies on first trapping its prey with its sticky, glandular hairs, as shown in Figure 1, before it slowly rolls up the edges of the leaf. It does not fold like the Venus fly trap, but it can effective enclose small flies with the numerous hairs.

The sundews, so named because their glandular leaf hairs glisten like dew in the sun, are not only common in bogs, but can occur on sandy banks and other mineral soils poor in organic nitrogen and phosphorus. So fascinating is this tiny plant that Darwin (1875) spent 285 pages of his book on insectivorous plants describing his own experiments on it.

Ca. 152 Listed Species
D. acaulis Linné (1781) | D. adelae F. Muell. (1864) | D. admirabilis Debbert (1987) | D. afra Debbert (2002) | D. alba Phillips (1913) | D. aliciae R. Hamet (1905) | D. androsacea Diels (1904) | D. anglica Huds. (1778) | D. arcturi Hook. (1834) | D. arenicola Steyerm. (1952) | D. ascendens St. Hil. (1824) | D. barbigera Planch. (1848) | D. bequaertii Taton (1945) | D. bicolor Lowrie & Carlquist (1992) | D. binata Labill. (1804) | D. brevicornis Lowrie (1996) | D. brevifolia Pursh. (1814) | D. broomensis Lowrie (1996) | D. browniana Lowrie & N. Marchant (1992) | D. bulbigena Morr. (1903) | D. burkeana Planch. (1848) | D. burmanni Vahl (1794) | D. caduca Lowrie (1996) | D. callistos N. Marchant & Lowrie (1992) | D. camporupestris Rivadavia (2003) | D. capensis L. (1753) | D. capillaris Poir. (1804) | D. cendeensis Tamayo & Croizat (1949) | D. chrysolepis Taub. (1893) | D. cistiflora L. (1760) | D. citrina Lowrie & Carlquist (1992) | D. closterostigma N. Marchant & Lowrie (1992) | D. communis St. Hil. (1824) | D. compacta Exell & Laundon (1955) | D. cuneifolia L. f. (1781) | D. curviscapa Salt. (1939) | D. darwinensis Lowrie (1996) | D. derbyensis Lowrie (1996) | D. dichrosepala Turczaninov (1854) | D. dielsiana Exell. & Laundon (1956) | D. dilatatopetiolaris K. Kondo (1984) | D. echinoblastus N. Marchant & Lowrie (1992) | D. elongata Exell & Laundon (1955) | D. eneabba N. Marchant & Lowrie (1992) | D. enodes N. Marchant & Lowrie (1992) | D. ericksoniae N. Marchant & Lowrie (1992) | D. erythrogyne N. Marchant & Lowrie (1992) | D. esmeraldae (Steyerm.) Maguire & Wurdack. (1957) | D. esterhuyseniae (Salt.) Debbert (1991) | D. falconeri K. Kondo & P. Tsang (1984) | D. felix Steyerm. & L. B. Smith (1974) | D. fimbriata De Buhr (1975) | D. fulva Planch (1848) | D. gigantea Lindl. (1839) | D. glanduligera Lehm. (1844) | D. graminifolia St. Hil. (1824) | D. graniticola N. Marchant (1982) | D. grantsaui F. Rivadavia (2003) | D. graomogolensis T. Silva (1997) | D. grievei Lowrie & N. Marchant (1992) | D. hamiltonii C. R. P. Andrews (1903) | D. hartmeyerorum Schlauer (2001) | D. helodes N. Marchant & Lowrie (1992) | D. heterophylla Lindl. (1839) | D. hilaris Cham. & Schlecht. (1826) | D. hirtella St. Hil. (1824) | D. hirticalyx R. Duno & Culham (1995) | D. huegelii Endl. (1837) | D. humbertii Exell. & Laundon (1956) | D. humilis (Planch.) (1848) | D. hyperostigma N. Marchant & Lowrie (1992) | D. indica L. (1753) | D. insolita Taton (1945) | D. intermedia Hayne (1800) | D. intricata Planch. (1848) | D. kaieteurensis Brumm.-Ding. (1955) | D. katangensis Taton (1945) | D. kenneallyi Lowrie (1996) | D. lanata K. Kondo (1984) | D. lasiantha Lowrie & Carlquist (1992) | D. leioblastus N. Marchant & Lowrie (1992) | D. leucoblasta Benth. (1864) | D. linearis Goldie (1822) | D. longiscapa Debbert (2002) | D. lowriei N. Marchant (1992) | D. macrophylla Lindl. (1939) | D. madagascariensis DC. (1824) | D. mannii Cheek (1990) | D. meristocaulis Maguire & Wurdack (1957) | D. microphylla Endl. (1837) | D. microscapa Debbert (1991) | D. miniata Diels (1904) | D. moaensis C. Panfet (1991) | D. modesta Diels (1904) | D. montana St. Hil. (1824) | D. monticola (Lowrie & N. Marchant) Lowrie (1992) | D. moorei (Diels) Lowrie (1999) | D. myriantha Planch. (1848) | D. natalensis Diels (1906) | D. neesii Lehm. (1844) | D. neocaledonica R. Hamet (1906) | D. nidiformis Debbert (1991) | D. nitidula Planch. (1848) | D. nivea Lowrie & Carlquist (1992) | D. oblanceolata Y. Z. Ruan (1981) | D. orbiculata N. Marchant & Lowrie (1992) | D. ordensis Lowrie (1994) | D. oreopodion N. Marchant & Lowrie (1992) | D. pallida Lindl. (1839) | D. paradoxa Lowrie (1997) | D. parvula Planch. (1848) | D. pedicellaris Lowrie (2002) | D. peltata Thunb. (1797) | D. peruensis T. Silva & M. D. Correa (1982) | D. pilosa Exell. & Laundon (1956) | D. platypoda Turczaninows (1854) | D. platystigma Lehm. (1844) | D. praefolia J. G. O. Tepper (1892) | D. prolifera C. T. White (1940) | D. prostratoscaposa Lowrie & Carlquist (1990) | D. pulchella Lehm. (1844) | D. purpurascens Schlotthauber (1956) | D. pycnoblasta Diels (1904) | D. pygmaea DC. (1824) | D. radicans N. Marchant (1982) | D. ramellosa Lehm. (1844) | D. rechingeri Strid (1987) | D. regia Stephens (1926) | D. roseana N. Marchant & Lowrie (1992) | D. rosulata Lehm. (1844) | D. rubrifolia Debbert (2002) | D. salina N. Marchant & Lowrie (1992) | D. sargentii Lowrie & N. Marchant (1992) | D. schizandra Diels (1906) | D. scorpioides Planch. (1848) | D. sessilifolia St. Hil. (1824) | D. sewelliae Diels (1904) | D. silvicola Lowrie & Carlquist (1992) | D. slackii Cheek (1987) | D. spilos N. Marchant & Lowrie (1992) | D. stelliflora Lowrie & Carlquist (1992) | D. stenopetala Hook. f. (1853) | D. stolonifera Endl. (1837) | D. subtilis N. Marchant (1982) | D. sulphurea Lehm. (1847) | D. tentaculata Rivadavia (2003) | D. tomentosa St. Hil. (1824) | D. trinervia Sprengel (1820) | D. tubaestylis N. Marchant & Lowrie (1992) | D. uniflora Willd. (1809) | D. venusta Debbert (1987) | D. villosa St. Hil. (1824) | D. viridis Rivadavia (2003) | D. walyunga N. Marchant & Lowrie (1992) | D. whittakeri Planch. (1848) | D. yutajensis R. Duno & Culham (1995) | D. zeyheri Salter (1940) | D. zigzagia A. Lowrie (1999) | D. zonaria Planch. (1848)

TRAP TYPE: Snap Trap
One species, Dionaea muscipula J.Ellis (1768), occupying habitats in the southeastern United States of America (North Carolina, South Carolina).

The steel trap of Dionaea is hardly as powerful as the ones set by trappers for wolves, beavers or bears, but it is just as effective at catching its own small prey. Figure 1 shows the traps ready to spring. Its growth in the wild is restricted to the bogs in the central southeastern coastal plain of the United States. Figure 2 below is a Venus flytrap in its natural environment.

Near the crease where the two leaf "jaws" join there is a series of tiny hairs. If an unwary insect walks across these hairs, touching two or more of them in succession, the leaf will close quickly enough to prevent its escape. Unable to escape between the hair-like teeth at the edge of the leaf (Figure 3), the helpless insect is slowly digested and absorbed by the leaf. Glands on the leaf surface secrete several digestive enzymes that help to decompose the insect. Once the insect has been digested sufficiently, the leaf re-opens for another victim.

The sensitive hairs at the fold of the leaf prevent the leaf from closing every time a drop of rain lands on it, because the leaf requires that two or more of these hairs be triggered in succession (Figure 3). If the leaf does close without a victim, it will re-open in a few hours. According to Lloyd (in George 1962), the traps can only catch about three victims before the leaves turn black and die. And even if the trap fails to catch anything, like when you tease it by touching a hair with a small brush, it can only reopen and close again about seven times! So, don't tease the flytrap!

The mechanism of closing has fascinated biologists for many years. How can an inanimate plant react so quickly to the stimulus of touch? The most widely accepted explanation had been that a rapid change in the turgidity of the cells occurs. That is, there must be a sudden change in the water pressure in the cells – the cells of the bottom part of the midrib, that is. Now we know that it is not nearly so simple, nor is our old explanation valid, although the lower midrib cells do indeed take in more water. In Dionaea, the closing occurs in as little as a half second. Salisbury and Ross (1985) explain the phenomenon as acid growth.

Early theories on the acid growth suggested that potassium or sodium must rush into the lower midrib cells to create an osmotic gradient. That means there is more salt inside than outside the midrib cells, and more water outside those cells than inside. However, Hodick and Sievers (1989) provided evidence that a change in turgor pressure due to movement of potassium or sodium was not the cause, but they were unable to provide any evidence to support an alternative theory.

Nevertheless, we now we have a somewhat clearer picture, but it still is only a collection of circumstantial evidence without direct links to demonstrate cause and effect. First the hairs are triggered, two in succession, and these triggers set up a change in the electrical potential, sending a signal to the lower cells of the midrib. Then a flurry of things happen so fast that we don't know what happens first. The growth hormone IAA appears in the midrib in increased concentrations. Hydrogen ions move rapidly into the cell walls of the midrib in response to action potentials from the trigger hairs (Salisbury and Ross (1985)).

We can only guess what happens here, but a good guess would be that a proton (H⁺) pump moves H⁺ ions out of the midrib cells and into the cell wall spaces between the cells. (Cell walls are really lots of fibers hooked together, creating a network of small capillary spaces.) Hydrogen ions naturally make this area more acid. These hydrogen ions seemingly loosen the cell walls, probably by dissolving the calcium pectate that glues the cellulose together, causing the tissues of the lower side of the midrib to be come flaccid. Calcium (not potassium or sodium as thought earlier) increases inside the cells and the cells absorb water.

It seems reasonable that this calcium might move into the cells by following the charge gradient. After all, if H+ ions left, the cell now has negative charges (electrons) that have no positive partner; the cell has a negative charge. This negative charge will attract positively charged things (positive ions, or cations) from outside the cell, like the Ca⁺⁺ (calcium ions) that were freed from the calcium pectate bonds of the cellulose fibers. Once the calcium enters the cell, it creates an osmotic gradient. There is now a greater proportion of Ca⁺⁺ and smaller proportion of water (H₂O) on the inside of the cells than on the outside of the cells in the cell wall spaces. The result? Water enters the cells by osmosis. Since the cells have become unglued, they are able to expand as they take in water, and hence they grow.

This results in the expansion of the outside of the leaf and the "springing" of the trap. Yes, all this happens at lightning fast speed to make the leaf close. The cells remain at this larger size and the cellulose eventually increases to strengthen the walls. That gets the trap closed, but in a few days, it must re-open. Once the insect is digested, the cells on the upper surface of the midrib will grow, much more slowly, and the leaf will re-open.

As you might imagine, the leaf cannot keep doing this rapid growth trick forever. That is why it is only able to close its trap about seven times during the life of a leaf. But why does it do this at all? In its boggy peatmoss habitat, nutrients are very limited. It can't use the nitrogen in the atmosphere (neither can we!), but it does need some form of nitrogen. Experiments on the Venus flytrap by Roberts and Oosting (1958) suggest that perhaps it is the organic form of nitrogen and phosphorus that is important to the insectivorous plants. And the trapped insects give them just that.