The Gist of Science Reporter Magazine: April 2013

Contents

• Indigenous Cryogenic Engine Must Be Developed Fast
• Brids Could Boost Agricultural Prospects
• Drug Dose
• Phases of Clinical Trial
• Soil in the Sunderban
• Mangrove Vegetation

INDIGENOUS CRYOGENIC ENGINE MUST BE DEVELOPED FAST

With the launch of GSAT-10 ASSISTED BY THE Ariane -5 rocket from French Guyana, ISRO completed its 101st mission on 29 September 2012. This geosynchronous satellite is the heaviest of all the satellites launched by ISRO,weighing 3,400 kilograms. Prior to this, ISRO ,  completed its hundredth mission on 9September 2012 with the help of PSLV-C21-the launch of the French satellite Spot -6 weighing 712 kilograms and the Japanese microsatellite Proiteres weighing 15 kilograms.

The polar Satellite Launch Vehicle (PSLV), considered to be the workhorse of ISRO, comes in three versions. Besides the standard version, the CA (core alone ) and XL ( extra large ) versions of PSLV have also been developed by ISRO. While the standard and the XL variants of PSLV have six strapon booster motors, no such motors exist in the CA variant. Besiders, the CA variant has 400 kilograms less propellant as compared to the standard version. PSLV (XL) has 12 tonnes of profellant in its six strap –on notors as against the standard version that has only 9 tonnes. In the hundredth mission of ISRO that took place on 9 September 2012. PSLV (CA) was used on its eighth mission. The standard version of PSLV has been used in eleven missions, including its first mission on 20 September 1993 that failed. PSLV (XL) has so far been used in three mission: the Chandrayan-1 mission on 22 October 2008, the launch of GSAT-12 on 15 July 2011, and more recently, the launch of RISAT-A on 22April 2012. Thus, PSLV has been used in a total of 22 mission including its firs failed mission in 1993. It has launhed 27 Indian and 20 foreign satellites, making a total of 55 satellites in all. The recent launch of geosynchronous satellite GSAT-10 from French Gutana has cost the exchequer a whooping amount of 750 crores. Evidently, this launch has raised one pertinent question, namely, why should we not fast equip the Geosynchronous Satellite Launch vehicle (GSLV) with the indigenous cryogenic engine? Of course, the development of Mark-II and Mark-III cryogenic engines is already going on in the country. While Mark-II has a lifting capacity of 2,500 kilograms, the Mark-III engine can lauch payloads weighing (GTO) and payooads weighing 10,000 kilograms in the Low Earth Orbit (LEO). A mark- II engine was even deployed in the sixth flight of GSLVD3 on 15 April 2012 to launch the GSAT-4 Satellite weighing 2,200 kilograms. However, as the engine did not ignite this mission failed.

The test flying of Mark-III took place recently in 2012. There are plans of using GSLV-Mark III in the Indian manned mission to Moon after Chandrayan-2 which is likely to be launched using Mark-II engine in 2014.

The launch of GSAT-6 satellite to take place some time in 2013 may also use Mark-II engine. However, ISRO must fast track the development of both these cryogenic engines. In the present scenario, there is hardly any option left. With only one Mark-I (c) engine left out of a total of seven cryogenic engines that we received from Russia, ISRO has to complete the development of cryogenic engines at a faster pace. It is necessary to become self- reliant in the field of space technology; otherwise, we would have to depend on foreign satellites for launching our INSAT/GSAT types of  satellites. Faster development of cryogenic engines is also necessary on another count.

At present, the INSAT/GSAT system has 168 transponders. There is a gross shortage of transponders due to which ISRO has been compelled to lease 95 transponders from foreign countries. Although GSAT-10 has added 30 transponders to the present fleet, there is still a dearth of transponders. Therefore, to augment the fleet of transponders also we need to launch the INSAT/GSAT types of satellites with the help of Indian cryogenic engines. We cannot be complacent in the matter.

BIRDS COULD BOOST AGRICULTURAL PROSPECTS

Althrough India’s growing population is expected to require additional food grain of about 2 million tonne per year, recent reports reveal that production losses through insect pests, diseases and weeds have shown an increasing trend over the years. Annual crop losses due to insect pests and diseases alone are estimated to be 18% of the agricultural output. During 1983, the losses due to insect pests were estimated around Rs. 6,000 crores, which increased to Rs. 20,000 crores in 1993 and to 29,000 crores in 1996.obviously, controlling the insect pest in agriculture is a major concern. However, researchers have expressed concerns about the safety of the increasingly used pesticides and recommended finding an effective alternative such as bio pesticide and biocontrol.

It is a sad irony that the importance of birds in Indian agriculture sector is poorly studied till date. In the past, birds were considered a serious threat to standing crops like paddy, corn and gram as well as the stored agriculture products. Invariably all the birds that visit the field are viewed as crop pests or predators. But this is only partially true; astonishingly the damage ratio is negligible as compared to the benefits.

Birds play an economically significant role in agriculture environment by way of controlling weeds by consuming the seeds and preventing further invasion. Moreover, the insects that destroy the agriculture products in all the stages are effectively controlled by the insectivorous birds. Especially during the pest outbreaks, the birds are the only natural and eco-friendly saviours of the crop. Most studies have disclosed that major proportions of birds (60-80%) that utilze the agiculture land are Black Drongo, Pittas, Larks, Swallows, Indian Roller, Common myna, Common hoopoe, Tree pie, Pond heron, Cattle egret, Red Wattled lapwing, Barn owl, Spotted owlet and Kites.

For instance, Cattle egret, mainly feed on the orthopterans (51.1%) Isopterans (19.9%), other invertebrates (15.3%) and Acarina (0.4%) and vertebrates (2.0%). All the major preys of Cattle egrets were identified as serious pests in agricultural lands whit 88.7% pest status. It is estimated that every 100 prey cosumed by Cattle egrets could save 1,58,361.54 hectares of farmland in one scason. The application of pesticide in agriculture land is driving many common birds like Sarus crane and House sparrow to the verge of extinction. Moreover, in recent times farmlands have turned into bird hunting yards. Many people in delta districts have become consummate bird hunters. There is also a very good market for the poached birds in this region. A number of hotels regularly purchase the birds from the poachers, and the birds are available in nearby slaughterhouses and fish markets.

Unfortunately, the hunters target the most beneficial species such as Cattle egrets, Bitterns, herons, Sandpipers and Storks. The hunting reaches it peak during the rainy season, ploughing periods and weekends. The uncontrolled killing of this species might have a palpable effect on agriculture and might lead to frequent pest outbreaks. It is high time to adopt a roadmap to stop the brutal killing of birds from agricultural lands for which continuous awareness and monitoring programmes should be conducted. Forest and agriculture departments should join their hands to achieve these objectives.

Drug Dose

The response differs for all drugs in the intensity and types of effects according to the dose of the drug given the smallest dosage if the drug to show an effect is the threshold of the drug. The dose of a drug required to produce an effective response in 50% of the people tested is called the median lethal dose. The increased dosage is often detrimental to the individual, as a lethal dosage may be reached.

Types of drugs

Depending on the action and effect produced, the drugs are generally classified as:

Analgesics/antipyretics: an analgesic is a drug that relleves pain and an antipyretic lowers body temperature and diminishes fever. Prostaglandins are potent mediators of inflammation and pain, and these drugs act by reducing its production, paracetamol, Aspirin, Lbuprofen, Ketoprofen, Flurblprofen, Butorphanol, Carprofen, Nalbuphine, Oxymorphone, Pethidine, Diclofenac ,Sodium, Insomethacin etc are examples.

Antacids: antacids relieve indigestion by neutralizing stomach acids. Histamine stimulates the secretion of pepsin and hydrochloric acid in stomach, When gastric hydro choric acid reaches the nerves in the intestine, they signal pain. Most of the drugs based on bicarbonates or metal hydrochloric acid reaches the verves in the intestine, they signal pain, Most of the drugs based on bicarbonates or metal hydroxides perform a neutralization reaction, increasing the pH to reduce acidity in the stomach. For instance, Gelusil Contains aluminum hydroxide, magnesium hydroxide, polyduimethyl siloxane and silica. Drugs such as cimetidine and ranitidine prevent interaction of histamine with the receptors present in the stomach wall, Thus, these are rated as better antacids.

Anthelmintics: Anthelnintics are drugs that expel parasitic worms from the body by either stunnig killing them. They may also be called vermifuges or vermicides. Albendazole is effective against threadworms, roundworms, whipworms, tapeworms, and hookworms. Diethlycarbamazine is effective against eosinoghilia. Mebendazole is used to treat infections caused by pinworms, roundworms and hookworms. Nicolasamide is effective against tapeworms.

Antianxiety Drugs: These suppress anxiety and relax muscles. Examples include Diazepam, Azapirones, Barbiturates and pregabalin Benzodiazepines bind to specific receptors in the central nervous system and act as agonists. They enhance the action of neurotransmitter a-amino butryic acid, which decreases excitation in the limbic system.

Antibacterials: An antibacterial is a compound or substance that kills or slows down the growth of bacteria and is used to treat infection. Antibacterial drugs include the penicillin, cephalosporin and the carbapenems. Compounds that are still isolated from living organisms are the amino glycosides. Whereas other antibacterial, for example, the sulfonamides, the quinolones and the oxazolidinones are synthesized. Their mechanism of action includes inhibition of cell wall synthesis, inhibition of protein synthesis, inhibition of nucleic acid synthesis; inhibition of metabolic pathways and interference with cell membrane integrity of the bacteria thereby terminating them.

Antibiotics: Chemical substances produced by microorganisms ( bacteria, fungi and destroy other microorganisms are called antibiotic drugs. Thus, antibiotic therapy is “setting one thief against another”. Some antibiotics are effective only against limited types of bacteria. Others known as broadspectrum antibiotics, are effective against a wide range of bacteria. Although there are well over 100 antibiotics, the majority comes from only a few types of drugs. The main classes of antibiotics are Penicillin (such as penicillin and amoxicillin)’ Fluoroquinolones (ciprofloxacin, levofloxacin); Sulfonamlbes (co-trimoxazole and trimethor=prim)’ tetracyclines; aminoglycosides (gentamicin, kanamycin, neomycin, streptomycin, tobramycin, and apramycin), ciprofloxacin is broad-spectrum antibiotic. Aminoglycosides indterfere with protein synthesis. Amoxicillin acts typically by inhibiting the synthesis of bacterialcell walls.

Antidepressants: An antidepressant is a psychiatric medication used to alleviate mood disorders, such as major depression and anxiety disorders in the level of neurotransmitter viz. noradendin lowers signal sending activity and this leads to depression. The antidepressant inhibits the enzyme that catalyses the degradation of noradrenalin. If the enzyme is inhibited, this neurotransmitter is metabolized and can activate its receptor for depression. Some examples are Citalopram, Escitalopram, Fluoxetine, and paroxetine. Certain antidepressants like Amitriptyline, Doxepin, and Imipramine act by blocking the reptake of neurotransmitters such as nor epinephrine (noradrenalin) and serotonin.

Antidiarrhoeals: Drugs used for relief from diarrhea. Two main types of anti-diarrheal preparations are simple adsorbent substances and drugs that slow down the contractions of the bowel muscles so that the contents are propelled more slowly. Drugs such as morphine of codeine can be used to relieve diarrhea. A notable drug for the purpose of relief of diarrhea is Loperamide.

Antifungals: Antifungal drugs are used to treat fungal infection, the most common of which affect the hair, skin, nails, or mucous membranes, e.g. terbinafine and itraconazole. The drug interferes with a cytochrome enzyme necessary to generate ergo sterol, on essential component of the fungal cell membrane. Inhibition of its synthesis results I increased cellular permeabiliaty causing leakage of cellular contents.

Anthistamines: Anthistamines are drugs used primarily to counteract the effects of histamine, one of the chemicals involved in allergic reactions. Histamine causes allergy by binding to specific receptors. The drugs block these receptors so that the histamine messages are not received. The classic anthistamines are represented by chlorpheniramine, brompheniramine, diphenhydramine and dimenhdrinate.

Anti-hypertesives: They are drugs that lower blood pressure such as Quinapril hydrochloride, spironolactone, methyldopa, ramipril, vera-pamil hydrochloride, nicardipine hydrochloride, diltiazem hydrochloride and doxazosin maculate. Some of these drugs produce belief by way of vasodilatation. Other drugs are direct venous and arterial dilators.

Anti-inflammatory: These are drugs used to reduce inflammation- the redness, heat, swelling, and increased blood flow found in infections and in many chronic non-infective diseases such as rheumatoid arthritis and gout. Examples of drugs are diclofenac, difiunisal, etodolac, ibuprofen, indomethacin, ketoprofen, ketorolac, naproxen, oxaproin etc. Prostaglandins produced by the cells of the body promote inflammation, pain, and fever apart from other important body functions like supporting the blood clotting function of platelets etc. Anti-inflammatory drugs block the enzymes and reduce prostaglandins throughput. As a consequence, inflammation, pain and fever are reduced.

Antineoplastcs: Alkylating ogents like cisplatin, chlorambucil and carboplatin as well as oxaliplatin act by impairing cell function by forming chemical bonds with the amino, carboxyl, sulfhydryl and phosphate groups in biologically important molecules. Fluorouracil is an antimetabolite used to treat certain cancers. Mercaptopurine s a drug that interferes with certain metabolism and is used to treat acute lymphocytic leukemia. Cytotoxic drugs like actinomycin and anthracyclime have a toxic effect on cells and are commonly used in chemotherapy to inhibit the proliferation of cancerous cells.

Bronchodilators: These drugs open up the bronchial tubes within the lungs when the tubes have become narrowed by muscle sposms. Bronchodilators ease breathing in diseases such as asthma. Short-acting medications provide qick or “rescue” relief from acute bronchoconstriction. Long-acting bronchodilators help control and prevent symptoms. Examples of short acting ones are saldutamol, ephedrine or epinephrine and the long acting ones are salmeterol and formoterol,. Theophylline is a lonh- acting bronchodilator that prevents asthma episodes and is administered orally for severe asthma cases.

Cold remedies: Cold is a disease that “cures in seven days with medicine but takes one week if untreated”. Although there is no drug that can cure a cold. The aches, pains and fever that accompany it can be relieved by aspirin or acetaminophen often accompanied by a decongestant, antihistamine and sometimes caffeine.

Diuretics: Diuretics are drugs that increase the quantity of urine produced by the kidneys and passed out of the body, thus ridding the body of excess fluid. They reduce water logging of the tissues caused by fluid retention in disorders of the heart, a diverse group of compounds that either stimulates of inhibit various hormones that naturally occur in the body to regulate urine production by the didneys. Examples of diuretic drugs include furosemide, ethacrynic acid, torsemide, bumetanide, hydrochlorothiazide, acetazolamide and methazolamide and potassium canreonate.

Hypoglycemics: Hypoglycemics are drugs that lower the level of glucose in the blood. Oral hypoglycemic drugs are used only in the treatment of type 2 diabetes, which is a disorder involving resistance to secreted insulin. Type 1 diabetes involves a lack of insulin and requires insulin for treatment. There are now four classes of hypoglycemic drugs:

• Sulfonylureas – function by stimulating insulin secretion.
• Metfornim – effective only in the presence of insulin; it does not directly stimulate insulin secretion and its major effect is to increase insulin action.
• Thiazolidinedlones – such as Avandia and Actos reverse insulin resistance by acting on muscle, fat and to a lesser extent liver to increase glucose utilization and diminish glucose production
• Alpha- glrcosidase lnhibitors such as acarbose and Miglitol inhlbit the upper gastrointstinsal enzymes that convert sietary starch and other carbohydrates into simple sugars that can be absorbed. This slows the absorption of glucose after meals.

Drug Metabolism

Drug metabolism is the biochemical modification of pharmaceutical substances through specialized enzymatic reactions. Drug metabolism often converts cell soluble chemical compounds into more readily excreted polar products. Its rate is an important determinant of the duration and intensity of the medicinal action of drugs. The metabolic reactions include oxidation, reduction, hydrolysis, cyclization, and decyclization etc. subsequently these metabolites undergo conjugation reactions by binding with carboxyl (-COOL), Hydrocyl (-OH), amino (NH2), and sulfhydryl (-SH) guoups of enzymes. Products of conjugation reactios have increased molecular weight and are usually inactive. Chemicals play a vital role in controlling biochemical processes that lead to healthy or disease states. For each type of disease larhe number of medicinal options are available. It is difficult to judge, a priori, which drug and in what dose would be most suited for a particular patient.

The unfortunate part is that each drug takes tens of years for its joumey since inception to the medical shop. Extensive research, clinical trials and the long lead time for drug development causes the ultimate drug cost to become unaffordable for the common people, though effectively one kilogram of a drug, in principle, can produce one million tablets. However, thanks to chemists, a large number of diseases from the common cold to the deadly cancer have been brought under control, As new diseases emerge, they pose greater challenges for chemists and pharmacologists to identify, synthesize and formulate new drugs that can combat them.

Phases of Clinical Trial

Clinical trials are mainly divided into four phaseas. Phases I-III are pre-marketing studles and phase IV is the plst marketing study. The clinical trial is a teamwork and includes doctors, clinical phasrmacologists, pparaclinical staff, health care professionals and social workers. The team screens Volunteers for participation and owns the total responsibility for the safely of trial participants. The trial is started after approval of regulatory authorities and depends on the protocol approved by regulatory authorities.

Phase I : In the first phase, evaluation of the new drug is performed on a small number (20-25) healthy volunteers. If the drug is expected to have significant toxicity (as in case of anticancer drugs of anti-HIV drugs), the volunteers with particular disease are taken rather than healthy volunteers,

Phase II: In phase II, the drug is studied for the first time in patients with the target disease to determine its efficacy, thesetrials are divided into Early and Late phases, In Early ghase, a small number of patients (20-200) are studied in detail to observe the potential therapeutic benefits and side effects, in Late phase, trials are conducted on a larger number of patients (50-300) to snsur safety and efficacy of the new drug I a specific disease. Data of phase II is compared with that of standard drug (in market) used for the same disease.

Phase III: (confirmatory trial): These are large-scale randomized control trials in patients (250-1000 plus ) to further establish safety and efficacy.

Phase III trials are conducted by a large number of clinicians at different centers. It may take and average of five years to be completed. At the end of this trial statistical analysis is performed. And then, New DRUG APPPLECATION is filed to dug control authorities after satisfactory completion of Phase III trials.

Phase IV: (Post Marketing Study): Once approval is obtained to market the drug, Phase IV of the trials begins. It is the post licensing phase – field trial.

Phase IV has no fixed duration as it is the surveillance phase during the post marketing clinical use of the drug. This is based on reporting by all physicians, the performance of the drug is monitored for several years, immediately after marketing, to discover relatively rare side defects (e.h. congenital effects ) or previously unknown drug interactions or even a previously unknown therapeutic use detected by a chance discovery. Clinical trials are the safest way to find efficacious treatment, With increasing globalization many multinational companies are trying to conduct clinical trials in developing countries like India to reduce their cost- related inputs. This can provide new career opportunities to those interested in this field but it also raises concerns regarding safety issues of participants.

Sunderban Mangroves

Sunderban, the largest mangrove ecosystem in the world, is facing serious threats to its survival. Also threatened are a large number of endangered and globally threatened faunal species and local inhabitants who earn their livelihood.

SUNDERBAN is the largest mangrove ecosystem in the world, covering an area of about one million hectares, of which 60% is located in Bangladesh and the remaining in India. Located in the southern part of the state of West Bengal, it extends over the area from Dampier- Hodges line in the north to the Bay of Bengal and from the western embankment of the rivers lchhamati-Kalindi-Raymangal in the east to the river Hooghly in the west. The area included in the UNESCO World Heritage list in 1987 is a part of the famous Ganges Brahmaputra delta. The name ‘Sunderban” has probably been derived from the Sundari trees (Heritiera fomes) that once abundantly populated the Sunderban. Alternatively, it has been proposed that the name is a corruption of Sunderaban meaning ‘Sea Forest’.

Sunderban is made up of 102 small islands and is crisscrossed by several rivers like Hooghly, Ichhamati, Bdyadhari, Thakuran, Matla, Gosaba, Haribhanga, etc. Along with their rivulets and creeks. Out of the total area of the Indian Sunderban of about 410,000 hectares is occupied by mangrove forest and 178,100 hectares is water body. The entire forested area constitutes the Biosphere Reserve (declared on 29 March 1989). The present Sunderban National Park, with three sanctuaries, is an integral part of this biosphere. The Sunderban creates as unique ecological environment tat is composed of rich assemblages of both floral and faunal wealth, along with dense human habitation surrounding the forest core area. Human settlements in Sunderban are believed to have started at least four hundred years ago. It has a funnel-shaped landscape with numerous linear tidal mud flats and a network of tidal channels. The Sunderban mud flats are found at the estuary and o the deltaic islands wher low velocity of rivcer and tidal current occurs. The flats are exposed during the low tides and submerged in the high tides. The tidal action deposits silt back on the channels thus raising the bed and forming new islands and creeks contributing to an uncertain geomorphology. Due to the gentle slope of the coast and large tidal amplitude3, tidal water penetrates to an average distance of 110 kilometres inland from the shore line and din some areas, the effect of the tides is felt over 300 kilometres inland.

The Sunderban region has a warm humid climate. The average maximum and minimum temperature of this region is 400 C and 180C respectively, with an annual rainfall of about 1600 to 1800 millimetres. Sunderban receives rainfall during the southwest monsoon season (June to October), with occasional rainfall throughout the year. Rainfall is negligible in the winter months. Occasionally, during May and October, violent cyclonic storms accompanied with high sea waves and tides devastate the coastal Sunderban area.

Soil in the Sunderban

The active delta of the Sunderban contains different types of soil such as silty clay loams, sandy clay and loams, soil with organic and peaty deposits, swampy and marshy soil, also called as ‘mangrove soil’. The soil is oxygen deficient and nitrogen content is also low. Soil pH is more or less acidic, ranging from 5.4 to 7.8.

Although the soil contains adequate water , plants cannot avail of the water because of high concentration of salts ( mostly chloride, sulphate and bicarbonate salts of sodium, magnesium and calcium). The salinity of the surface soil is governed by the quantity of freshwater flow and monsoon rainfall, being highest in the middle of the summers and lowest during the rainy months. The Ganges and Brahmaputra, tow snow-fed rivers and their large number of tributaries and rivulets, supply a huge an=mount of freshwater to the Sunderban mangroves throughout the year. Because of this salinity of the water body within the mangrove forest as well as near the sea is lower than that of the sea water even during the summer months.

Mangrove Vegetation

Mangroves are flowering plantrs comprising atleast three types of floral components – true mangroves, back mangroves and mangrove associates. True mangroves are salt-tolerant halophytic plants, growing on tidal swamp habitats. The true mangrove species thrive in high salinity, daily submergence, fine clayey oxygen deficient soil, tidal currents, fresh water flow and strong wind as well. To adapt to the situation, they have stilt roots and supporting cable-like shallow holding roots that support the plant in tidal currents. True mangroves also possess pneumatophores to access atmospheric oxygen. Most of these plants possess salt-secreting glands in their leaves. Mangrove associates are not true mangrove plants. They are common mesophytic plants occurring near the human habitation. These plants can grow in nutrient- deficient soil but cannot withstand environmental conditions as encountered by the true mangroves. The freshwater river discharge coupled with high rainfall, the tropical humid climate and the less number of dry months all support plant growth. Hence, the species variety as well as biomass is obviously high in this region, in comparison to the rest of the mangrove wetlands in India. The interior parts of the mudflats are home to luxuriant mangroves. According to an estimate by the West Bengal Forest Cepartment, there are 84 species of true mangroves, mangrove found in the Sunderban mangrove forest, however, the distribution of species is not uniform and primarily controlled b the level of salinity and not by the tidal inundation. The true estuarine zone is dominated with species with tolerance to high salinity and submergence, including Jatbaen (Avicenniga officinalls), pairabaen (A. alba), kalabaen (A. Marina), Garia (Kandella candel), Kripa (Lumnitzera racemosa), Tora (Aegialtis rotundifolia), etc. The middle estuarine zone where the salinity is lower but the tidal current passing through the narrow creeks and channels is hgh is ddominated by Gaarjan ( Rhizophlra apiculata), Goran (Ceriops decadra),Mathgoran (C. tagal), Bakul (Bruguiera cylndrlca), etc. The inner estuarine zone comprising of elevated areas with less saline soil and more fresh water flow is dominated by Genwa ( Excoecaria agallecha), Kankra (Bruguiera gymnorrhiza), Khalsi (Aegiceras corniculatum), Ora (Sonneratia caseolaris) and Hental (phoenix Paludosa).

However, some mangrove plant species are rare, Endemic and restricted to specific salinity. The distribution of trees like Amur (Agalia domestica), Dhundul (Xylocarpus grandtum), Passur (X. mekongensis), Sundbri ( Heritiera fomes ) and Golpata ( Nypa fruticans ) palm-swamps are extremely limited. Among these species, Sundari and Golpata are very rarely sighted in the wild. Besides, plants like Amur, Passur, Tora, etc. are endemic to the Sundeban region only. Freshwater inflow in the western part of Sunderban has been reduced by geotectonic and fluvial reasons. This has caused the forest cover in this area to be less dense and discontinuous. The mangroves in this zone are dwarf as well as bushy types, like Hargoza ( Acanthus illcifolius), Ban Lebu (merope angulata) and Lata Sundari ( Brownlowla tersa).

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