eChapters

ALL LIVING ORGANISMS ARE MADE UP OF UNITS CALLED CELLS

All living creatures are made from 1 or more cells

All cells are produced from previously existing cells (no spontaneous generation)

All cells appear to be descended from the first cell which existed about 4 billion years ago

For a species to exist its reproductive cells must be potentially immortal (no aging)

Our bodies start from a single cell and contain about 100,000,000,000,000 (10^14) cells at maturity

I. WALL COMPONENTS – CHEMISTRY

The main ingredient in cell walls are polysaccharides (or complex carbohydrates or complex sugars) which are built from monosaccharides (or simple sugars). Eleven sugars are common in these polysaccharides including like glucose and galactose. Carbohydrates are good building blocks because they can produce a nearly infinite variety of structures. There are a variety of other components in the wall including protein, and lignin. Let’s look at these wall components in more detail:

A. Cellulose: β1,4-glucan (structure provided in class). Made of as many as 25,000 individual glucose molecules. Every other molecule (called residues) is “upside down”. Cellobiose (glucose-glucose disaccharide) is the basic building block. Cellulose readily forms hydrogen bonds with itself (intra-molecular H-bonds) and with other cellulose chains (inter-molecular H-bonds). A cellulose chain will form hydrogen bonds with about 36 other chains to yield a microfibril. This is somewhat analogous to the formation of a thick rope from thin fibers. Microfibrils are 5-12 nm wide and give the wall strength - they have a tensile strength equivalent to steel. Some regions of the microfibrils are highly crystalline while others are more “amorphous”.

COMMON FEATURES OF BIOLOGICAL MEMBRANES

Membranes are sheetlike, just a few molecules thick and form closed boundaries between cell compartments.

Membranes contain lipids and proteins, with small amounts of carbohydrayes linked to the lipids and proteins.

Lipids in membranes are small with hydrophobic and hydrophilic portions. Lipid bilayers provide a barrier to the diffusion of polar molecules.

Characteristic functions of membranes are mediated by specific proteins, serving as pumps, channels, receptors, energy transducers and enzymes.

Membrane components associate through noncovalent interactions.

Membranes are asymmetrical, with two sides of the membrane differing from each other.

Lipid and protein molecules often diffuse rapidly in the plane of the membrane.

Central transport of ions and molecules into and out of the cell.

Generate proton gradients for ATP production by oxidative phosphorylation.

Receptors bind extracellular signals and transduce the signal to cell interior.

ALL MOLECULES MOVE CONTINUOUSLY BY SIMPLE DIFFUSION

Heat energy causes molecules to move randomly (sometimes called Brownian motion)

If the concentration of molecules is different in 2 regions (this produces a concentration gradient), diffusion will cause molecules to move from a region of high concentration to one of low concentration

The higher the concentration gradient the more rapid the net diffusion

Diffusion evens out the concentrations so they are equal everywhere (maximum entropy)

If 2 different substances have the same concentration gradient, usually one will move faster than the other

Differences in speed between molecules with the same concentration gradient are given in terms of diffusion constants

A substance with a high diffusion constant moves faster than one with a low diffusion constant

In general, large molecules move slower than small molecules

Diffusion across a membrane is called permeability, and membrane diffusion constants are called permeability constants

Metabolism - sum total of all chemical reactions in living cells

Catabolic reactions - degrade macromolecules and other molecules to release energy

Anabolic reactions - used to synthesize macromolecules for cell growth, repair, and reproduction

Can divide metabolism into 4 groups: carbohydrates, lipids, amino acids, nucleotides.

MOST OF THE ENERGY FOR LIFE COMES FROM SUNLIGHT

Total rate of energy delivery from sun to earth (at the top of the atmosphere) = 175,000 terrawatts

Terrawatt = 10^12 watts

Rate of energy capture by plants from the sun = net primary productivity (NPP) = 100 terrawatts

Only ~ 0.06% of sunlight is captured

Captured in chemical bonds, especially in sugar

Small amounts of energy are available to specialized microorganisms from chemical reactions not linked to sunlight

It is estimated that 99% of the energy used by living cells comes from the sun

Incorporation of sunlight into chemical bonds occurs through the process of photosynthesis

“Invented” by cyanobacteria about 2 billion years ago

NEW CELLS ARE PRODUCED BY DIVISION OF PREVIOUSLY EXISTING CELLS

All cells come from previously existing cells

To make a new cell identical to itself a cell must perform 4 tasks:

It must grow and make additional copies of all its organelles, enzymes, etc..

It must duplicate its DNA

It must accurately separate the DNA into 2 units, so that each cell gets a full set

It must divide into 2 cells (cytokinesis)

SEX IS VERY COSTLY

Large amounts of energy required to find a mate and do the mating: specialized structures and behavior required

Intimate contact provides route for infection by parasites (AIDS, syphillis, etc.)

Genetic costs: in sex you pass on only half your genes to your children

Males are an expensive luxury- in most species they contribute little to rearing offspring

But There are Some Advantages

More genetic diversity: more potential for survival of species when environmental conditions change

Shuffling of genes in meiosis (random separation of homologous chromosomes)

Crossing-over in meiosis (see below)

Fertilization (genes from 2 individuals brought together)

A fair number of practical breeding experiments were done in ancient times

People knew there was a connection between sex and reproduction

The idea had developed that “like begets like”

By selecting certain plants and animals and breeding them many domestic varieties of plants and animals had been developed

Example: corn was developed from a wild grass in Mexico and Central America, probably about 5000 years ago

149 of the top 150 plant crops were domesticated by primitive man

MENDEL’S RULES OF GENETICS DO NOT ALWAYS WORK

Mendel’s rules:

Segregation of alleles

Independent assortment of genes for different characters

Hold for characters:

Which have dominant & recessive traits

Determined by single genes

Genes are on separate chromosomes

Different types of chromosomes, or

Different homologues of same type of chromosome

These conditions are not always met, so there are many complications

Chromosomes are giant molecules of DNA

Found in nucleus: never leave except in cell division

Carry hereditary units, genes

Two homologous copies in diplod cells

Unwind when replicating or making RNA

Wind up (condense) in cell division

Attach to spindle and separate in meiosis & mitosis

Crossing over in prophase of 1st meiotic division

Chromosomes are equally distributed in mitosis, meiosis

Gametes have half the number of chromosomes as body cells

Sister chromatids are observed to split apart longitudinally in anaphase

UNTIL THE 1940S BIOLOGISTS ARGUED ABOUT WHETHER DNA OR PROTEIN WAS THE MOLECULE OF HEREDITY

Nuclei observed to divide when cells reproduced themselves

Large amounts of both DNA & protein in the nucleus

Many though protein was most likely molecule of heredity

Proteins made of 20 different amino acids- could have more variety than DNA (made of only 4 different bases)

DNA replication. The double helix is unwound and each strand acts as a template. Bases are matched to synthesize the new partner strands.

DNA replication, the basis for biological inheritance, is a fundamental process occurring in all living organisms to copy their DNA. This process is “replication” in that each strand of the original double-stranded DNA molecule serves as template for the reproduction of the complementary strand. Therefore, following DNA replication, two identical DNA molecules have been produced from a single double-stranded DNA molecule. Cellular proofreading and error toe-checking mechanisms ensure near perfect fidelity for DNA replication.

In a cell, DNA replication begins at specific locations in the genome, called “origins”.

Unwinding of DNA at the origin, and synthesis of new strands, forms a replication fork. In addition to DNA polymerase, the enzyme that synthesizes the new DNA by adding nucleotides matched to the template strand, a number of other proteins are associated with the fork and assist in the initiation and continuation of DNA synthesis.

Viruses are much simpler than cells

Protein capsid

Genetic information stored on DNA or RNA:

Types of genome:

Double strand DNA: sometimes circular

Single strand DNA: sometimes circular

Double strand RNA

Single strand RNA

Some can be crystallized

BACTERIA HAVE SMALL, COMPACT GENOMES

We now know the complete DNA sequences for about a dozen bacteria

Bacteria seem to need about 500 to 5000 genes to conduct their lives

Because they are small, bacterial genomes are highly organized

Most of the time there are only a few bases between the end of one gene and the beginning of the next

Few introns are found in bacteria

Bacteria contain accessory “chromosomes” called plasmids; each has only a few genes

Restriction enzymes cut only at specific sequences of 4 to 8 bases

A long restriction site is rare. Cutting rare sites will produce a few large pieces of DNA.

Restriction enzymes with long sites → small number of large fragments

Restriction enzymes with short sites → large number of small fragments

The polymerase chain reaction (PCR) is a rapid way of amplifying (duplicating) specific DNA sequences

Method was devised by Kary Mullis of Cetus Corporation, Emeryville He recieved a $20,000 bonus and later a Nobel Prize

DNA heated to high temperature is not destroyed; separates into single strands, but reforms helix when cooled

PCR Method:

DNA to be amplified is put into solution containing:

WHAT IS PLANT?

A. Definition - by most definitions, a plant:

is multi-cellular;

is non-motile

has eukaryotic cells

has cell walls comprised of cellulose

is autotrophic; and

exhibits alternation of generations - has a distinctive diploid (sporophyte) and haploid (gametophyte) phase.

Water, of its very nature, as it occurs automatically in the process of cosmic evolution, is fit, with a fitness no less marvelous and varied than that fitness of the organism which has been won by the process of adaptation in the course of organic evolution.

WATER IS ABSOLUTELY ESSENTIAL FOR ALL LIVING ORGANISMS

The evidence:

Most organisms are comprised of at least 70% or more water. Some plants, like a head of lettuce, are made up of nearly 95% water;

When organisms go dormant, they loose most of their water. For example, seeds and buds are typically less than 10% water, as are desiccated rotifers, nematodes and yeast cells;

Earth is the water planet (that’s why astronomers get so excited about finding water in space).

Water is the limiting resource for crop productivity in most agricultural systems.

I. Definitions

Transpiration - evaporation of water from a plant surface

Evapotranspiration - evaporation of water from a plant surface and the soil (and abiotic surroundings.

Take-home-lesson: Plants loose a lot of water by transpiration. See text for some specific examples.

I. Definition

Solute transport in plants, translocation, primarily occurs in the phloem, but it can occur in the xylem.

II. Solute Transport in the Xylem

Some solutes are transported in the xylem

Water and dissolved ions are the main substances in vessels/tracheids

These materials are transported via transpiration stream

Xylem sap may also contain organic materials, usually in relatively low concentration (with a notable exception being maple sap in the spring which is comprised of 2% or more sucrose).

Substances move at different rates depending on matrix effects, metabolic needs, etc.

PLANT NUTRITION

Plants use inorganic minerals for nutrition, whether grown in the field or in a container. Complex interactions involving weathering of rock minerals, decaying organic matter, animals, and microbes take place to form inorganic minerals in soil. Roots absorb mineral nutrients as ions in soil water. Many factors influence nutrient uptake for plants. Ions can be readily available to roots or could be “tied up” by other elements or the soil itself. Soil too high in pH (alkaline) or too low (acid) makes minerals unavailable to plants.

Plant hormones - They are defined as:

1. Small
2. Organic compounds;
3. Synthesized by the plant;
4. Active in low concentration (<10^-6);
5. Promote or inhibit growth and developmental responses;
6. Often show a separation of the site of production and the site of action (although this isn’t as clear a distinction as in animals).

Based on these criteria, would the following substances be considered hormones? Ca²⁺, sucrose, 2 4 - D, glycine, or K⁺?

INTRODUCTION

The debate on climate change is going on. From the report of the Inter Governmental Panel on climate change (IPCC), a premier organization set up in 1998 by the World Meteorological Organisation and United Nations Environment Programme, it is known that the average surface temperature has increased over the 20th century by about 0. 6ºC. The number may seem insignificant but it is an unprecedented rise. In the past 150 years, the 11 hottest years were witnessed. It says that 1990s was the warmest decade and 1998 the warmest year since 1861. Worse, the Artic is warming twice as rapidly as the rest of the world and there is a distinct possibility of the Greenland Ice Sheet collapsing altogether and pushing up sea levels by several metres. It is predicted that 2035 is the year when Himalayan glaciers may totally disappear causing catastrophic disruptions. Unfortunately, India is among the countries that will suffer the most serious consequences as a result of global warming. Following is the probable effect of global warming.

INTRODUCTION

Research in agriculture and allied activities and the subsequent technological innovations are important requisites for enhanced productivity and generating income for the farmers. In India, farming is a way of livelihood to 65 per cent of nearly 1. 1 billion population. Our farm population is increasing annually by 1. 84 per cent. The average farm size is becoming smaller each year and the cost-riskreturn structure of farming is becoming adverse with the result that farmers are getting increasingly indebted. There is no option except to produce more food and other commodities under conditions of diminishing per capita arable land and irrigation water resource. Hence, we must harness the best in frontier technologies, thus integrate them with traditional wisdom and thereby launch an eco-technology movement.

The productivity in agricultural sectors is dependent on several bio physical and socio-economic factors. The significant biophysical factors are weather parameters, soil health, water resources, crops/ varieties and pest environments. In order to monitor the impact of weather parameters, we need to have weather forecasts and the accuracy of which to harvest the economic benefits should be given top priority. Only fifty years ago, weather forecasting was an art which was derived after interpretation of data received from land based observing stations, balloons and aircraft etc. Now, modern technology particularly computers / weather satellites / radars has resulted in enormous improvements in the accuracy of weather forecasting with the help of various coordinated meteorological observing networks.

INTRODUCTION

Inspite of recent technological developments which have helped to increase agricultural production in many countries, growth of plants and animals continue to depend to a large extent on the weather conditions. Each plant has its own climatic requirements for growth and development and any large scale deviation from it exert negative influence.

Growth of plants is most sensitive to temperature just above a threshold value and near the maximum value, where growth normally stops. Therefore, periods of extreme temperature i. e. low temperatures below the threshold value and high temperatures above the maxima are hazardous to plant development and growth. Extreme temperature conditions during cold spells cause stress and frost; high temperatures lead to heat stress, and both affect agricultural production. Snow and ice storms in late spring or early autumn are very hazardous to many temperate crops.

Similarly extremes of moisture conditions namely dry desiccating winds, drought episodes and low moisture conditions as well as very humid atmospheric conditions including wet spells tend to affect agriculture. High soil moisture situations of water logging and flooding associated with heavy rainfall and tropical storms have adverse effect on plant growth and development since they influence the rate of transpiration, leaf area expansion and ultimately plant productivity. Drastic changes in rainfall variability can have very significant impact, particularly in climatically marginal zones such as arid, semi-arid and sub-humid areas where incidence of widespread drought is frequent. Dry desiccating and strong winds reduce agricultural production as a result of very high evapotranspiration rates. It also causes mechanical damage to plant with weak stems by lodging such as the sugarcane and the banana.

INTRODUCTION

In spite of technological developments for the last few decades, Indian agriculture is still rain dependent. Extreme weather events such as drought in 2002, cold wave during 2002-03, heat wave in the year 2003, increased temperatures during rabi 2003-04 and 2004-05, deficit rainfall in many parts of the country during 2004 and excess rains in 2005 (100cm in Mumbai, floods in MP, Gujarat, Orissa, AP, Tamilnadu and Karnataka) could affect the food grain production considerably. The spatial and temporal changes in important weather parameters such as rainfall, temperature, wind, cloud cover, humidity, etc. would influence crop yields by affecting farmers’ decision in selection of cultivar, use of inputs, crop management practices, etc. These decisions significantly influence the aggregate agricultural output, which , in succession has an impact on the economy of the country as a whole. Thus, the timely and accurate weather based agro -advisories is the need of the hour for sustainable agricultural production.

Further, the quality of utility of agro-advisories can be improved through value addition to the agromet information including forecast and demonstration of economic benefits accrued due to the following of the advisories. Thus making farmers to adapt weather-based advisories for (i) Increasing the quality and quantity of produce, (ii) Efficient utilization of resources, (iii) Minimizing losses due to adverse weather, (iv) Effective utilization of favourable weather events, and (v) Reducing cost of cultivation to enhance profits.

INTRODUCTION

The discipline of Agrometeorology, an applied science is less than fifty years old. Its services are operationally used by individual farmers in developed countries, and by agricultural or development services in more than half of the countries of the world. Its contribution to agricultural production by examining forecast is sought in virtually all countries. In many countries, the respective governments have expressed the desire to use meteorological information to a much larger extent in day-to-day farm planning and operations. The climate database is used for the development of practical criteria in planning and management of irrigated and rainfed crop production system (Martin Smith, 2000).

Though a huge set of Agromet data exists in India, its utility has not been effective due to the scattered location of these data sources and the impediments for free flow of data to the users to analyze and interpret for real-time decision making in agriculture. There is also a considerable time lag between the actual observation and data availability. In view of the importance and the immediate exigency to centralize the database system for helping the researchers and planners, a central agrometeorological databank facility funded by DST from 1998 to 2003 and later by ICAR with the following objectives was established at Central Research Institute for Dryland Agriculture (ICAR), Hyderabad.

INTRODUCTION

India is endowed with a vast and rich diversity of natural resources particularly soil, water, climate and agro-biodiversity. To realize the optimum potential of the agricultural production system on a sustainable basis, there is a need to bestow a paramount importance in the arena of efficient management of natural resources. India with a geographical area of 329 M ha presently supports 17% of the world’s population on merely 2. 5% of world’s land area and 4% of world’s freshwater resources. India’s economy is predominantly agrarian in nature with about 72. 2% of its 1028 million population (census 2001) living in villages and about 54. 4% people (cultivators) directly depending on agriculture.

INTRODUCTION

Any crop has its own optimal requirements or selective response to the environmental factors such as rainfall/ soil moisture supply, day/night air temperature, soil temperature, duration of sunshine and its intensity. The growth and development of a plant which ultimately governs the agricultural productivity of a region, is closely related with climatic factors. Weather phenomenon has a profound influence on crop growth stage. A moderate wind or a light rain, when the crop growth is near to harvest, may do more damage than even heavy rain and high wind in the vegetative phase. So land use planning by matching crop growth with weather parameters forms a basis for successful agriculture (Samra, 2003) in a particular region. In order to achieve sustainable agricultural productivity in the 21^st century, the climate and weather systems are being recognized as critical agenda and input.

INTRODUCTION

The agriculture in north eastern hill region of India is mainly rainfed in nature and shifting cultivation, known as jhuming, is the dominant farming system. The shifting cultivation is detrimental to both soil and vegetation as it is connected to heavy soil and nutrient losses when practised in steep slopes. The burning and slashing operations are responsible for reduced floral and faunal diversity in the region. It is a well known fact that climate is the main driving factor that governs the sustainability of other natural resources such as land, water and vegetation. So far the NE region gets abundant rainfall for survival of the crops at least during the kharif season. The rainfall starts early March and continues up to the late October. The jhum cultivators follow the rainfall trend and get their field ready for sowing of seeds by early March itself so that vegetative stage of crops gets plenty of rainwater for growth and development. Due to increased population pressure, the hills of NE region are over exploited and the jhum cycle has been reduced from 10-12 years to 4-5 years now-adays. Hence the soils do not get sufficient time to revitalize it and are subjected to more and more exploitation and get degraded permanently.

INTRODUCTION

Of an estimated 142 mha of net cultivated areas in India, about 67 % is rainfed and only 45 mha is irrigated. The NCA (1976) predicted that even when the full irrigation potential of the country is exploited by 2013 AD, over 50% of arable land would continue to remain rainfed in future. It is the rainfed belt where cultivation of 91 % coarse cereals (Sorghum, Pearl millet and Finger millet), 91% pulses (Chickpea and Pigeon pea), 80% oilseeds (Groundnut, Rapeseed, Mustard and Soybean) and 65% cotton have predominated. Even the crop that formed the backbone of green revolution such as rice and wheat, still have 50% and 19% area under rainfed condition, thus emphasing the importance of rainfed agriculture in India. Inadequate resource (soil and rain water) management coupled with traditional farming practices are responsible for subsistence farming. Monocropping, traditional crops and their varieties, low and imbalance nutrients and inadequate crop establishment, in past, had been the major cause for poor development of dryland agriculture in the eastern region.

INTRODUCTION

Rubber cultivation in regions extending from 10°N to 10°S latitude is known as the traditional region and the areas other than its natural climatic origin is termed as the non-traditional region. Northeast India comprises majority of the non-traditional areas in India with major climatic constraints like high seasonal rainfall, excessive precipitation and to some extent dry conditions. These areas extending from 22 to 29^°N latitude, holds promise in extending rubber cultivation because of its exceptional climatic make-up and abundant amount of annual precipitation (2000 mm) distributed over a fair period of time.

This perennial crop generally yields latex rubber at the 7th year after planting (with an economic life span of 20 years), although the period (immaturity period) it requires, is higher in the non-traditional region (Rubber Growers Companion, 2006). This immaturity period has also been shown to reduce with water availability in sub-humid climates (Vijayakumar et al. , 1998). Harvest of this crop is by tapping. Tapping is a process of controlled wounding during which thin shavings of bark are removed, thus opening the latex vessels which exude latex. Dry rubber yield is obtained after the latex is coagulated and rolled into sheets (about 500gm) which is then smoked and dried.

INTRODUCTION

The weather conditions during the growing season of crops influences the onset and development of disease. The relationship between weather and plant disease development is the basis for meteopathological forecasting. On the basis of observed or forecast weather conditions, the incidence of plant disease is likely to be predicted.

Such predictions are designed to warn growers of expected significant developments in the manifestation of a particular plant disease. Such disease forecasts, if sufficiently accurate, permit efficient and competent counter measures to be adopted. A short range or medium range of disease forecast, issued at short intervals during the growing of crops, can give guidance to the farmers on the best remedial measures. Growers can decide whether a chemical control measure is needed or not, and if needed then optimum date on which to be applied and similar day to day decisions to fight against disease to minimize the losses to be caused.

The result, of adopting such a plan of weather based control measures, is to reduce the number of chemical sprays to a well timed few, thus giving an equal or even better protection at a lower cost in chemical and labour, and simultaneously reduces losses caused by phytotoxic and mechanical damage to the crop. The reduction in the use of potentially toxic chemical is a matter to be welcomed in the present world, considering the consequences of the widespread use of toxic chemicals.

INTRODUCTION

Integrated Pest Management (IPM) has been defined as a “system that, in the context of the environment and the population dynamics of the pest species, utilizes all suitable techniques and methods in as compatible manner as possible that maintain the pest populations at levels below those causing economic injury” (Glass 1975). The Inter society Consortium for Plant Protection (ICPP) has defined integrated pest management as “the use of multiple tactics in a compatible manner to maintain pest population at levels below those causing economic injury while providing protection against hazards to humans, domestic animals, plants and the environment”. The term ’integrated’ means it is a broad interdisciplinary approach taken using scientific principles of plant protection of variety of management strategies and tactics to fuse into a single system. The terms ‘pest’ means all biotic agents which adversely affect plant production. This includes insects, mites, nematodes, weeds, bacteria, fungi, viruses, parasitic seed plants and vertebrates. The term ‘management’ indicates to keep the pest population below some level based on economic criteria. It does not mean complete eradication of entire pest population.

INTRODUCTION

Mizoram is a hilly terrain lying in the north eastern part of the country. The total geographical area of the state is 21, 087 sq. km and lies between 92º 15/ to 93º 29/ E longitude and 21º 58/ to 24º 35/ N latitude. Out of six agro climatic zones of the NEH region, Mizoram comes under sub tropical hill zone and posses a sub tropical and humid climate due to high rainfall (Fig. 1). These climatic conditions are very conducive for the cultivation of a large number of agri-horticultural crops. The physiography of the state is divided into hills and valley lands. About 90 % area of the state comes under hills and only 10 % area is under valley. The valley lands are sporadically distributed in small patches except in Champhai district. The slope of the hills in Mizoram is much steep as compared to the other states in the North Eastern region. The land use statistics of the state is presented in Table1.

INTRODUCTION

Several biophysical factors govern the agricultural productivity of a region. Among the key biophysical factors, weather and more particularly rainfall has the over riding impact on agricultural productivity since rainfall is a primary source of water and the first requirement for raising any crop. This element influences various dynamics of crop growth and development and accounts from nearly two thirds of variation in agricultural productivity. The amount of rainfall at a particular place is important; an equal important factor is its temporal distribution, which is uneven, uncertain and erratic in most part of the country. Breaks in monsoon are common phenomenon during the monsoon period. The analysis of rainfall characteristics such as occurrence and distribution of dry or wet spell is essentially required for successful crop planning, development of befitting agro techniques, recommendation of suitable crop variety, designing of water harvesting ponds, earthen dams and other soil conservation structures. It is also an established fact that the crop development will be affected if the dry spell coincides with sensitive phonological stage of the crop and sometimes beneficial if it coincides with the ripening stage. Hence for the purpose of crop planning and to carry out the agricultural practices, it is important to know the sequence of dry and wet periods. An attempt has been made in this paper to analyse the rainfall in standard meteorological week as well as monthly basis at different probability levels for Lembucherra by using computer based forecasting technique.

INTRODUCTION

The state of Manipur is located at the easternmost border of India and is characterized by flat valleys comprising of four valley districts (Bishnupur, Imphal East, Imphal West and Thoubal) surrounded by five mild to steep slope hill districts (Chandel, Churachanpur, Senapati, Tamenglong, and Ukhrul). The state is geographically bordered by Nagaland in the north, Burma in the east, Mizoram in the south and Assam in the west. The total geographical area of the state is 22, 327sq. km divided into 20, 089sq. km in the hills and 2, 238sq. km. in the valley. More than 98% of the population in the hill is in rural areas whereas around 60% of the population in the valley is in rural and around 40% are in the urban areas.

The AAS Unit, Imphal is located at 24045' N latitude, 93054' E longitude at an altitude of 774m above msl. The agro-climatic zone of the state covers sub tropical plain zone, sub tropical hill zone, temperate hill zone and sub temperate zone.

INTRODUCTION

It is well accepted that the climatic changes also influence the geomorphic process efficiency and landform development (Ahamad, 1985). Glaciation, sea level changes, flooding and many other geo- environmental events are related with global and regional climatic changes along with tectonic and other non-tectonic factors like natural vegetation, soil, organic development etc. Considering the role of climate on landform development and dynamics of the Late Quaternary climate, a climato-geomorphic study was conducted on the coastal and paleo-coastal areas of the Bengal Basin namely-lower Western (West Bengal coast) and Eastern (Tripura Paleo-coastal Fold Belt Province) Geo-provences. The main objectives of the study were to investigate (i) Development of the landforms during Late Quaternary period with sea level changes and (ii) Climatological influences on the landform modifications.

INTRODUCTION

India has varied agroclimatic conditions, which favour the cultivation of various horticultural crops. Based on the adaptability and system of cultivation, the horticulture can be grouped into four major class such as Temperate, Sub-tropical, Tropical and Arid. India has become the second largest producer of both fruits and vegetables with a total production of 46. 75 million tonnes of fruits from an area of 4. 56 million ha and 93. 16 million tonnes of vegetables from 6. 30 million ha (2003-2004). Besides, there is a tremendous scope for increasing the production of flowers, spices and condiments, plantation crops and medicinal and aromatic plants. Floriculture has emerged as a viable agribusiness. The commercial cultivation of flowers in open field conditions was much popular than protected cultivation in India. But, now- a-days, the protected cultivation has brought a great revolution in Indian floriculture and it helps for the quality production and export to earn sizeable amount of foreign exchange. India has approximately 350 ha under green house cultivation with export value of approximately Rs. 330 crores during 2003-04(APEDA). On the other hand, the prevailing climatic conditions in India are highly suitable for cultivation of the almost all spices from tropical black pepper to temperate saffron. The major spices are mainly grown in humid tropics like Western Ghats and NE States. Out of 21 agro-ecological sub regions in India, spices are grown in 14 different agro ecological sub regions. Fruits, vegetables, flowers spices and condiments, plantation crops and medicinal plants are widely distributed across the country, while plantation crops are restricted to a few regions.

INTRODUCTION

Edible mushrooms are higher fungi occurring seasonally all over the world in various habitats varying from sandy plains to thick forests. About 2000 fungal species in the world have been identified as edible, of which, only a few (20) are cultivated commercially (Chang and Miles, 1991). These mushrooms are generally considered as the good source of protein, vitamins and minerals in addition to their flavour and condiment value. About 3.

INTRODUCTION

Livestock plays a very important role in the mixed farming system of the country contributing about 25 per cent of Gross Domestic Products (GDP) from agricultural sector. India has the largest population of cattle and buffaloes and the highest producer of milk in the world. India has also the second largest population of goats and one of the leading countries in poultry sector. There has been a tremendous increase in milk, meat and egg production since independence. However, owing to various reasons viz. , low genetic potential, scarcity of feeds and fodders, diseases, poor management practices etc. , the productivity is quite low. Climatic conditions of a place have also an important bearing on livestock production and productivity. Climatic factors like ambient temperature, humidity, solar radiation and wind velocity are the important ones which make up the physical environment of the animal having direct and indirect influences on animal’s responses towards climate. Temperature and humidity are the most crucial with the former being the most researched one. Extremes of hot and cold weather are creating stress to any animal and the effects are more severe under hot and humid climate. The varied effects of undesirable climate on animals are pertaining to feed and water intake, physiological, biochemical and endocrinological aspects, reproduction, health and productivity etc. Thus, the positive and negative effects of the environment on the livestock have been discussed in a way to undertake some protective measures.

INTRODUCTION

Prediction of helminthic infections is impractical. The aim of any control programme must therefore, ensure that parasite populations do not exceed levels compatible with economic production. The parasitological monitoring (e. g. faecal egg counts or pasture sampling) at intervals, forecasting on the basis of meteorological data and computer simulation may provide an alternate approach to control parasitic infection (Brunsdon, R. V. , 1980) in a given geographical area. The most common gastrointestinal parasite prevalent throughout the year in Meghalaya, India is Strongyle infection. This is because of the high rainfall and humidity prevalent in the North-Eastern region.

As the prevalence of this infection is mainly dependent on rainfall and humidity, study was being initiated to identify the relationship between rainfall/temperature and strongyle infection. The study would be also helpful in predicting/ forecasting the disease occurrence based on the prevailing pattern of rainfall in a particular location.

INTRODUCTION

One of the most important changes in the global environment which affects the existence of all living things , is the climate change. The climate change globally and locally also changes the aquatic habitat which, in turn directly and indirectly affects the environment. Anyway, the changes in climate are certain to occur and may be inevitable. The only possible way is to analyze the situation and find out the reasons for such changes and take immediate steps to minimize the impact of these climate changes. Global warming has eventually become synonymous with climate change because almost all the variables of the ecosystem are influenced directly or indirectly at different levels.

Aquatic environment is extremely diverse and influenced by the climate changes to a large extent both locally and globally. The changes in the ocean and its life are well studied at different levels with all possible details compared to the freshwater habitats. Unlike agriculture and animal husbandry, the vast majority of the fish production still comes from the natural habitat or the wild collections. Agriculture and animal husbandry usually focus on few important species but for fisheries, all the species of fishes including most of the aquatic living organisms are commercially important. The media (water) in which the aquatic organisms dwell, is much more important to all living organisms of the earth and so the influence by climate changes on water becomes very much relevant in the present situation. Freshwater habitats are limited and are much more complex to investigate in respect of climate changes due to the variability and diverse micro and macro level interactions. A holistic approach to deal with all these problems has not got much attention both globally and locally even though , it is the need of the hour to address the issues of impact of climate changes in the aquatic environment.

INTRODUCTION

Aquaculture had undergone rapid expansion and intensification in the recent past and has taken the shape of a full-fledged diversified industry. But the risk involved in aquaculture activity has also increased significantly due to the outbreak of diseases which has a devastating effect on the aquaculture crops. Fish are aquatic and poikilothermic, their existence and performance are dominated by the quality of their environment . The aquatic environment is a complex system subject to constant physical and chemical changes brought about by natural and manmade processes. Therefore, choosing the proper site to develop aquaculture facility is paramount to its success.

A disease is an abnormal condition of an organism caused by infection, inherent weakness or environmental stress; it prevents the organism from functioning normally which ultimately leads to death (Avault, 1998). In an aquatic environment, there is a profound balancing of relationship between host (fish), pathogen and the environment existing and this is the fundamental concept to disease susceptibility of fish (Snieszko, 1973). A disease organism may be present in the environment or host, but will not cause disease as long as the host has high natural resistant or the physical condition of the host is strong. Once the imbalance is created to any of the component, opportunistic pathogen invades the host resulting to the outbreak of disease.

1.1 Introduction

Greenhouse effect, regulated by the presence of greenhouse gases in the earth’s atmosphere, is a natural process that plays a major part in shaping the earth’s climate. A continued rise in concentration of the greenhouse gases has led to enhanced greenhouse effect resulting in global warming and global climate change. The impact of human activities on greenhouse gases (GHGs) emission through fossil fuel burning, agriculture and industrial processes is important and familiar to people. This chapter addresses basic principles and physics of greenhouse effect and the role of Indian agriculture in GHG emissions. Agriculture is a potential source and sink to GHGs in atmosphere. It is a source for three primary GHGs: CO₂, N₂O and CH4 and sink for atmospheric CO₂ . Management of agricultural land, land use change and forestry has a profound influence on atmospheric GHGs concentration. The two broad anthropogenic sources of GHGs emission from agriculture are the energy use in agriculture (manufacture and use of agricultural inputs and farm machinery) and the management of agricultural land. Large sections of the India’s population depend on biomass resources like wood, crop residues and cattle dung for energy. In the agriculture sector, besides the CO₂ emissions due to burning of crop and animal waste, India’s large ruminant population and rice fields are significant contributors to CH₄ emissions. An understanding of GHG emissions by sources and removal by sinks in agriculture is important to take appropriate mitigation and adaptation strategies and to estimate and create inventory of GHGs.

2.1 Introduction

Weather has always been a popular topic but in the recent past it has received wide attention and debate as the public concern has increased about unforeseen changes in our climate. Over the 20^th century the average temperature of the earth has increased by 0.4 -0.8^oC. This increase is expected to continue and by 2100 the average global temperature is likely to be 1.4 - 5.8 ^oC warmer. One of the anticipated effects of climate change is the possible increase in both frequency and intensity of extreme weather events, such as heat waves, cold waves, hurricanes, floods and drought spells. The warming of the earth may fuel interactions between the ocean and atmosphere that will amplify the frequency and intensity extreme weather events. The possible changes in the frequency, distribution and intensity of extreme climate events have a significant influence at local, regional and global scales due to their multi-sectoral impacts on the overall economy.

3.1 Introduction

Ozone (O₃) is present throughout the atmosphere and can have either positive or negative effect depending on where it is found. The stratosphere (15-50 km) has the largest (90%) concentrations of O₃ (Colls, 1997). Stratospheric O₃ is important as it regulates the transmittance of ultraviolet light to the surface of the earth. Hence reductions in stratospheric O₃ in Polar regions, particularly the Antarctic “ozone hole”, are of concern regarding the health effects of exposure to increased levels of ultra violet (UV) radiation. In the troposphere (0-15 km), O₃ is a toxic pollutant of global importance and it is a major constituent of photochemical smog. Interest in pollutant O₃ and in its effects on living organisms has increased in the last decades as a consequence of the rise in its ground-level concentration and of the widening of its diffusion (Ashmore, 2005). Economic growth requires more energy production, which would result in increased production of NOx and volatile organic compounds (VOCs) precursors for O₃ formation (Ghude et al., 2008).

4.1 Introduction

Circumstantial evidences almost confirm researchers’ on early predictions of a changing climate and a warming world. The trend of changes also establishes the primary influence of increased greenhouse gas concentration on the global warming and the consequential events. The global mean surface air temperature has increased by about 0.74°C over the last 100 years. It is projected to rise 1.4 to 6.4 °C by the year 2100 (IPCC AR4, 2007). Changes will vary from region to region. Eleven of the twelve years in the period 1995-2006 rank among the top 12 warmest years in the instrumental record (since 1880). The radiative forcing of CO₂, CH₄ and N₂O is very likely (> 90% probability) increasing at a faster rate during the current era than any other time in the last 10,000 years. This is because of the increase in the global abundance of the three key greenhouse gases. The atmospheric CO₂ concentration has reached the level of 389 ppm in 2010 (WMO, 2011) from 270 ppm the pre-industrial era. In addition, global abundance of other greenhouse gases such as methane (CH₄) has increased from 700 ppb in the pre-industrial era to 1808 ppb in 2010 and in the same period, nitrous oxide (N₂O) has increased from 270 ppb to 323 ppb.

5.1 Introduction

In recent decades, human induced changes in climate of the earth have the focus of scientific and social attention. The most imminent of this is the increased concentration of greenhouse gases (GHGs) namely, carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) in the atmosphere. The concentration of CO₂, CH₄ and N₂O have increased markedly by 30%, 145% and 15%, respectively as a result of human activity since 1750, the era of Industrial Revolutions (IPCC, 2007). Between 1750 and 2005, the concentration of CO₂, CH₄ and N₂O in the atmosphere has increased from 280 to 379 ppm, 715 to 1774 ppb and from 270 to 319 ppb, respectively (IPCC, 2007). However, there was a steep increase during the recent years i.e. 70% increase of GHGs between 1970 and 2004.