The Attraction System Adopted by the Pitcher in Nepenthes Rafflesiana - Essay Example

Nepenthes Rafflesiana Trap Structure Saad Bin Zafar College This essay explores the details of pitcher trap present in Nepenthes Rafflesiana. The paper initially tells us about the genus and family of the plant and its habitat. It also briefly discusses the structure of the trap, describing the mouth and body in detail. Furthermore the paper explains the development of the trap and the different stages. The ecology of the plant is also presented which is then related to the nutrient deficiency and the modification and adaptation of the plant. Finally it explains the different theories behind the different mechanism by which this trap works involving the processes of attraction, trapping, retaining, digestion and absorption. Keywords: Nepenthes Rafflesiana, Pitcher trap Nepenthes Rafflesiana of genus Nepenthes which belong to the family of Nepenthaceae are one of the most famous carnivorous plants having pitcher traps (Slack & Gate, 2000). Nepenthes have a total of more than 100 species with the bulk of species populated along the islands of Borneo and Sumatra (Bonhomme et al., 2011). Nepenthes pitcher plants including Nepenthes Rafflesiana have also developed specific adaptations like all other carnivorous plants due to lack of nutrients. This nutrient deficiency is a result of the habitat in which these plants grow and they are mostly dependant on insect derived nitrogen (Gaume, Gorb & Rowe, 2002). As a result Nepenthes have these pitcher traps in order to catch and trap insects and then getting the nourishment by digestion and absorption. The structural architecture of the traps of Nepenthes Rafflesiana varies according to the geometry and surface features (Gaume et al., 2002). The pitcher trap is generally composed of three distinct parts (Gaume & Di Giusto, 2009). The three parts named as peristome, waxy zone and digestive zone are all involved in their respective functions of attention, capture and digestion. A lid known as operculum is present above the peristome. The lid prevents the rain water from accumulating inside the pitcher and thus helps to prevent nutrient loss. According to Di Guisto et al. (2010) Nepenthes Rafflesiana show heteroblastic development defined by pitcher dimorphism according to their growth and maturity. Terrestrial pitchers or lower pitchers are linked to the young species whereas the aerial or upper pitchers are associated with the mature and climbing life forms. The two pitchers thus also show different characteristics. While the aerial pitchers are elongated, shaped like a trumpet and greenish yellow in colour the terrestrial pitchers are more winged shaped, globular and reddish green in colour. Aerial pitchers have an approximate length of 3-12 inches while terrestrial pitchers are around 3-10 inches long. The pitcher traps mostly develop during summer. Although most leaves have a trap it is not a necessity that a leave must have a pitcher trap. Often due to lack of light, low humidity or difficulties in cultivation might cause a leaf to not develop a pitcher trap. The initial sign of pitcher formation is a swelling on the tendril of a recently formed leaf. Leading towards maturity this minute swelling becomes filled with air and the first sign of colouring appears on it. A few days after the variegation appears, the lid of the pitcher opens and they become operational. In a week time the walls of the pitcher strengthen and they finally become completely mature. The pitcher trap consists of a mouth and a body. A hard, glistening and rounded collar or rim makes up the mouth of the trap (Bauer and Federle, 2009). This rim is frequently furrowed with very apparent and obvious parallel ribs. Each and every rib ends inside the mouth in a very sharp downward direction. The angles created due to this downward pointing, house single nectar secreting glands between them. The body of these traps also varies from pitcher to pitcher. The body is more or less like a cylinder with a rounded base. The lower half of the body is often more bell shaped than the rest of the body. The wings of terrestrial pitchers earlier mentioned become bordered by hairs after maturation and are their most conspicuous feature. The aerial pitchers on the other hand are characterized by various ridges extending from the rim towards the tendril. Below the pitcher the interior consists of the waxy and digestive areas (Bauer and Federle, 2009). The waxy zone makes up to one third of the interior area while the digestive zone makes up to two third. The two areas have different anatomical and histological features (Gaume & Di Guisto, 2009). The waxy zone consists of different modified stroma. The stroma contains a hypertrophied guard cell having a convex structure in order to prevent interlocking with an insect’s claw. On the other hand the digestive zone has a smooth and glandular appearance containing numerous microscopic glands which are responsible for the secretion of digestive fluids and juices and absorption of the food as a result of this digestion. Nepenthes Rafflesiana can be described as a scrambling vine. The stem is very long and may reach up to a height of 15 meters with a thickness of just 10 millimeters. The flowers of the plant are usually borne in racemes and are often not visible to the eyes. They are about 3 mm in size and are mostly present in green or red colour. Another feature of this plant which exhibits two different forms is the presence of hair. The young life forms are completely covered by long brown and white hairs while the mature ones only have an indumentums of short brown hairs. Also Nepenthes Rafflesiana has weak roots due to its different modifications and adaptations and thus absolute care must be taken during repotting. This plant along with all other Nepenthes species is dioecious permitting only one sex in every plant. In their research article Adam, Wilcock & Swaine, (1992) have described the ecology of the Nepenthes genes and its species including Nepenthes Rafflesiana. Two classifications have been presented. The low lying forms of the plant mainly grow in open areas such as bushes and ferns at road side embankments, edges of the forest and swampy areas. The highland species are more populated among the montane rain forest. Nepenthes Rafflesiana though, mainly grows in open areas like waterlogged areas or deep shaded forest areas. As discussed above the habitat and the ecosystem in which Nepenthes Rafflesiana grows forces it to adapt to nutrient deficiency and thus modification arises in the form of pitcher traps which allow the plant to fulfill its need for nitrogen through another source namely in the form of arthropods, insects and some time small vertebrates like rats. The ecological relationship exhibited by this species is that of a predator and prey. Simply speaking the mechanism behind the working of pitcher traps revolves around the concept of attraction, catching, trapping, digestion and absorption. The different components of the trap complete these tasks for the plant. Below we discuss in detail the mode of action of these parts in light of different researches through a period of time. The attraction system adopted by the pitcher in Nepenthes Rafflesiana is believed to be quite similar to the method used in pollination by the plants (Di Guisto et al., 2010). This system usually depends on two things; attraction through colour patterns and use of volatile compounds to charm and entice the insects. Di Guisto et al., (2010) further mentions that an olfactory signal is involved in this attraction process and this signal helps in expanding the prey spectrum. Gaume and Di Guisto, (2009) have argued the role of waxy surface in the trapping of insects by Nepenthes. For decades the waxy zone has been considered the key trapping device since it minimizes the adhesive prowess of insects. This is because of the presence of a rough surface and the non-cohesive structure of the wax crystals. With the former weakening the point of contact and the latter contaminating the tarsel pads of insects the waxy zone is really important. However new studies have pointed out new properties of some other parts of the pitcher traps highlighting their importance in the trapping and retaining mechanism. The peristome has a very important part to play in this capturing process. As it is highly wettable it allows water droplets to spread very quickly and form homogenous films acting very slippery for the insects and preventing close contact of the surface with the tarsel pads of the insects (Bauer, Bohn & Federle, 2008). Moreover another property playing a part in the trapping mechanism is the viscoelasticity of the digestive fluid in Nepenthes Rafflesiana (Gaume and Forterre, 2007). This causes the insects to sink as they are easily drawn into the pitchers. The efficiency and proficiency of capture and digestion is very vital for maturity and survival of the plant. The enzymes present in the digestive juices of these pitcher traps include proteases, chitinases, phosphatases and glucosidases (Takeuchi et al., 2011). The study further also states that free living microbes are present within the pitcher playing a part in the production of these digestive enzymes. Going through all these research articles one comes to the conclusion that there is still plenty of prospects for further researches in the proposed structure and mechanism of pitcher traps in Nepenthes Rafflesiana. However the present studies very clearly show the importance and also explain the working of these traps for the benefit of the plant. References Adam, J. H., Wilcock, C. C. & Swaine, M. D. (1992). The ecology and distribution of Bornean Nepenthes. Journal of Tropical Forest Science, 5(1), 13-25. Bauer, U. & Federle, W. (2009). The insect-trapping rim of Nepenthes pitchers: Surface structure and function. Plant Signaling & Behavior, 4(11), 1019-1023. Bauer, U., Bohn, H. F. & Federle, W. (2008). Harmless nectar source or deadly trap: Nepenthes pitchers are activated by rain, condensation and nectar. Proceedings of the Royal Society of Biological Sciences, 275(1632), 259-265. Bonhomme, V., Pelloux-Prayer, H., Jousselin, E., Forterre, Y., Labat, J. & Gaume, L. (2011). Slippery or sticky? Functional diversity in the trapping strategy of Nepenthes carnivorous plants. New Phytologist, 191, 545-554. Gaume, L. & Di Guisto, B. (2009). Adaptive significance and ontogenic variability of the waxy zone in Nepenthes Rafflesiana. Annals of Botany, 104, 1281-1291. Gaume, L. & Forterre, Y. (2007). A viscoelastic deadly fluid in carnivorous pitcher plants. PLos ONE, 2(11), 1-7. Gaume, L., Gorb, S. & Rowe, N. (2002). Function of epidermal surfaces in the trapping efficiency of Nepenthes Alata pitchers. New Phytologist, 156, 479-489. Di Guisto, B., Bessiere, J. M., Gueroult, M., Lim, L., Marshall, D. J., Hossaert-McKey, M. & Gaume, L. (2010). Flower-scent mimicry masks a deadly trap in the carnivorous plant Nepenthes Rafflesiana. Journal of Ecology, 98, 845-856. Slack, A. & Gate, J. (2000). Carnivorous Plants. Massachusetts: The MIT Press. Takeuchi, Y., Salcher, M. M., Ushio, M., Shimizu-Inatsugi, R., Kobayashi, M. J., Diway, B., Mering, C. V., Pernthaler, J. & Shimizu, K. K. (2011). PLos ONE, 6(9). Read More