eChapters

An amine reacts with a carboxylic acid to form an amide. Similarly, the amino group  on one amino acid molecule reacts with the carboxyl group of another amino acid  to form a compound called peptide. A peptide bond is an amide bond that forms when the –COO- group of one amino acid reacts with the -NH₃+ group of another amino acid. The resulting compounds are called peptides. Even after this there is a reactive amino group and a carboxyl group in the peptide. If these groups react further a poly peptide can form and later a polymer called protein can form.

Amino acids are the building blocks of proteins. They occur in all living plant cells as constituents of proteins and as free acids or amides. More than 200 naturally occurring amino acids have been identified in higher plants. Around 20 different amino acids have been observed to be incorporated into proteins. They have two functional groups, an amino group (-NH2) and a carboxylic group(-COOH). Both these groups are attached to the a carbon atom only. Amino acids with this structure are called a amino acids or 2-aminoacids. The unique characteristics of the 20 amino acids are due to the side chain (R), which can be an alkyl, hydroxyl, thiol, amino, sulphide, aromatic, or heterocyclic group.

Amino acids have the general formula, R-CH(NH₂)-COOH. The R represents a side chain. If R=H, the simplest amino acid glycine (NH₂ -CH₂ –COOH) results. Amino acids are alpha (a ) amino carboxylic acids. The carbon atom is tetrahedral in shape. The various groups attached to it are placed in different positions. Since the valence of the carbon atom is four, four groups can be attached to the carbon atom. Based on the groups attached to the carbon atom it may be of two types.

Lipids are non polar substances of biological origin that are sparingly soluble in water, but soluble in organic solvents like chloroform, hexane, benzene etc. The word lipid comes from the Greek word lipos meaning lard or fat. The lipids present in biological systems are either hydrophobic (non polar) or amphipathic (both polar and non polar). Lipids like fats, oils or glycerophospholipids can be hydrolyzed to get fatty acids and other products. Hydrophobic nature is useful in making lipids as membranes which act as effective barriers to more polar molecules. Steroids are also considered lipids, but cannot be hydrolysed and are components of non-saponifiables in fats. Waxes, which are esters of fatty acids with long chain alcohols are also considered as lipids.

Carbohydrates are the most abundant biomolecules on earth. They occur in nature as glucose, starch and cellulose etc. Each year, photosynthesis converts more than 100 billion metric tonnes of carbon dioxide and water into starch, cellulose and other plant products. Carbohydrates are polyhydroxy aldehydes or ketones and their derivatives. They provide 4k calories energy per gram. They promote utilization of lipids and reduce wastage of proteins. They are readily available in roots, tubers, cereal grains, sugarcane and sugar beet.

Carbohydrates have the general formula C_n( H₂O)n, indicting that they are the hydrates of carbon. Some carbohydrates also contain nitrogen, phosphorous or sulfur. They are characterized by the number of carbon atoms they contain. If n=3, they are trioses, n=4 tetroses, n=5 pentoses, n=6 hexoses and n=7 heptoses. The most common sugars in plants are the hexoses. Two or more simple carbohydrates condense together to form polymer sugars like sucrose, starch and cellulose etc. The basic condensing bond is glycosidic bond.

All living organisms are basically made up of chemical components. The chemistry, composition and energy management of living organisms is what we call biochemistry. It tries to explain life processes at the molecular level. Although different organisms differ outwardly in their life processes, there are striking similarities in executing the different tasks. Genetic code, metabolic pathways, enzymes, coenzymes and even regulatory mechanisms are similar to a large extent in all the living organisms. Living organisms have certain extraordinary properties. They can grow, respond to stimuli and replicate themselves with high fidelity. All these activities are ultimately interpretable in chemical terms. The components that constitute organisms are all inanimate. The lifeless organic molecules with appropriate complexity and properties make a living being.

Biochemistry helps us understand how the inanimate molecules that constitute living organisms interact with each other to maintain life. The basic life processes or the biochemistry remains broadly the same in either the unicellular microorganism or the higher organisms such as the plants or the human beings. Life is nothing but thousands of ordered chemical reactions. In other words, chemistry is the logic of all biological phenomena.

Many surgeons have made attempts to develop minimally invasive surgical techniques with minimum blood loss and fewer traumas, to treat the disease process and minimize patient morbidity. Laparoscopic surgery may provide a wide field of its extensive application particularly in surgical sterilization of different animal species. Furthermore, high demographic urban and industrial area requires an effective animal birth control programme, which can overcome the problem of hospitalization, postoperative complications, and the overall cost reduction of operation. The sterilization of (both male and female) is effective measure in controlling the stray dog’s problem. Because the sterilization of either male or female alone is not effective and also sterilization of female consume more time when compared to male sterilization. To combat stray dogs in Animal Birth Control (ABC) programme, it is effective to sterilize the male also. Castration of male dogs by conventional open method has many disadvantages and postoperative complications such as hemorrhage, wound dehiscence, infections, maggot infestations and scrotal swellings etc. In a large scale Animal Birth Control programme, the conventional methods of sterilization requires a long period between capture of dogs and their release due to the time taken for the surgical wounds to heal. In this aspect, Keyhole surgery (Laparoscopic surgery) can revolutionize the entire programme, as it needs only very small surgical wound, which usually needs no postoperative care or regular dressings. It also avoids postoperative complications such as wound dehiscence, herniation, etc. and reduces the surgical stress to animal as well as recurring cost of each surgery.

Anaesthesia is an important criterion for doing laparoscopic procedure, which is being achieved by induction of general anaesthesia. However, in certain species, e.g. bovine, caprine etc., it can be done by preanaesthetic agent and infiltration of the local anesthetic agent at the site of the trocar placement. Selection of an anesthetic agent depends on the patient conditions, nature of procedure; time to be taken for the laparoscopic procedure and available facility. For the induction of the general anaesthesia follow the same procedure as in the conventional surgery viz. fasting, water withheld, preanaesthetic, fluid administration etc. Further, due to difference in the physiology of cardiopulmonary system of different animals, all these considerations varied from species to species and breed-to-breed. For instance cattle and buffalo are more prone to regurgitation and subsequent aspiratory pneumonia in general anaesthesia than those of dog and cat. While going for induction of general anaesthesia, an anesthetist should know about the different drug being used, their mechanism of action, effect on the different body system, their adverse effect and pure antagonist, if possible. Besides this an anesthetist should also know about the patient physiology and equipment for the administration of the anesthetic agents, because veterinary anesthetist is faced with numerous disturbances of cardiopulmonary and skeletal muscle function associated with general anaesthesia. For anaesthesia no anaesthetic agent is safe until and unless it is used by an experienced anesthetist.

14.1. INTRODUCTION

The climate of a place is the average weather that is experiences over a period of time. It is the natural phenomenon that has occurred throughout the history of the earth. Climate change is strongly associated with higher temperature, altered precipitation, and higher levels of atmospheric CO₂ and other greenhouse gases. It is a very slow process; it takes a long time to settle in. Climate change in IPCC (2007) usage refers to any change in climate over time, whether due to natural variability or as a result of human activities. Over the last 150-200 years the changes to our climate are happening more quickly now than they have ever done before in the geological past. Human activities have altered natural climatic processes at a geographically rapid pace by booting atmospheric concentrations of several greenhouse gasses. Following are the changes taken place over years of industrial age (IPCC, 2007):

13.1. INTRODUCTION

Photosynthetically active radiation is a primary energy resource for terrestrial plants, necessary for the plant growth. Plants receives this photosynthetically active radiation from sunlight as a consequence, plants are also exposed to the ultraviolet (UV)-radiation. Seven percent of the electromagnetic radiation emitted by the sun is the UV range (200-400 nm). Though representing only a small portion of the total solar electromagnetic spectrum, UV-B has a disproportionately large photobiological effect. As it passes through the atmosphere, the flux transmitted is greatly reduced, and the composition of the UV-radiation is modified. This UV-radiation is mainly divided into three classes, namely UV-A, UV-B and UV-C. The UV-A region of the spectrum (wavelengths from 320 to 400 nm) are not attenuated by ozone, so their influence will be unaffected by ozone layer reduction. This portion of the UV radiation is less damaging and important for photomorphogenic signal in plant development (Bjorn, 1994). The wavelength of UV-B portion ranges from 280 to 320 nm. This region of UV is very energetic and effectively absorbed by ozone in the stratosphere. Thus, only a very small portion, approximately 4% is transmitted to the earths. Shortwave UV-C radiation (200-280 nm) is highly energetic and strongly absorbed by atmospheric oxygen and ozone. Thus, none of this sterilizing radiation is present in terrestrial sunlight.

12.1. INTRODUCTION

Air is polluted when it contains enough unhealthy particles and gases to harm human beings, animals, plants and even objects such as building and statues. Air pollutant may present as solid, liquid or gas form. Industrial revaluation in the 19th and 20th centuries leads faster increase in concentration of air pollutants in the atmosphere. The most important air pollutants that damage the plants’ growth and development, subsequently the economic yields of crop plants are ozone (O₃), nitrous oxides (NO₂ and NO), carbon monoxide (CO), ammonia (NH₄), peroxiacetyl nitrate (PAN), sulphur dioxide (SO₂), hydrogen fluorides (HF), particulate matters (cement dust, magnesium-lime dust, carbon shoot etc.), smoke etc. Burning of hydrocarbons in motor vehicle engines gives rise to CO₂, CO, SO₂, and NO in varying proportions and ethylene (C₂H₄) as well as other hydrocarbons. Industrial plants release SO₂, H₂S, NO₂ and HF into atmosphere. Hydrogen peroxide (H₂O₂) is another potentially injurious molecule, can form by the reaction between O₃ and naturally release volatiles (terpenes) from forest trees.

11.1. BORON TOXICITY
11.1.1. Introduction

Boron (B) is essential micro-nutrient. It is necessary for cell wall formation, membrane integrity, calcium uptake and carbohydrate synthesis and transportation. B affects many functions in plants, which includes flowering, pollen germination, fruiting, cellular activities (division, differentiation, maturation, respiration etc.), water relationships and the movement of hormones. It is not translocated and leached easily from soils.

10.1. CADMIUM
10.1.1. Introduction

Cadmium (Cd) is a strongly phytotoxic heavy metal in an increasing environmental problem worldwide. It is one of the most dangerous metal due to its high mobility and the small concentration at which its effects on the plants being to appear. It is released into the environment by the power stations, heating systems, metal-working industries or urban traffic. It is recognized as an extremely significant pollutant due to its high toxicity and large solubility in water (Pinto et al., 2004). Soil solutions which have a Cd concentration ranging from 0.32 to 1.00 mM can be regarded as polluted to a moderate level (Sanita di Toppi and Garbrielli, 1999).

9.1. INTRODUCTION

Iron (Fe) is important component of a plant’s energy-power house chlorophyll. It also interacts with all the major enzymes and proteins at higher concentration in the soil, and it is toxic to plants. Fe-toxicity creates a range of nutrient disorders and deficiencies of P, K, Ca, Mg, Mn and Zn in plants. These elements were reported to play decisive roles in manifesting toxicity symptoms in rice (Sahu, 1968; Ottow et al., 1983; Yamauchi, 1989; Sahrawat et al., 1996). Excess absorption and translocation of Fe in the rice plants led to toxicity, which has been a major limiting factor in wetland rice. Average yield loss due to Fe-toxicity accounts to 50% and in fact ranges from 10-100% (Brigit et al., 1993).

8.1. INTRODUCTION

Aluminium (Al) is not considered as essential nutrient, but at low concentrations it may increase plant growth or induce other desirable effects (Bollard and Butler, 1966; Foy, 1988; Huang et al., 1992a, b; Roy and Mandal, 2005). Al affects about 40-70% of the world arable land, which has the potential for food crops biomass production (Haug and Caldwell, 1985). Acid soils constitute about 3.95 billion hectares globally. About 38% of those are present in Tropical Asia (Datta, 2002). It is believed to cover more than 800 million hectares of forest and tropical Savana ecosystems of tropical America (Jaffe and Rojar, 1994; Prakash 2000). Nearly 75% of Amazon Basin contains acid and infertile soil classified as oxisols and utisols. About 383 million hectares (79%) of the Amazon area, suffers from Al toxicity. Acid soil occurs extensively in the some of the Mediterranean countries and Southern Australia. Low laying acid sulfate of Bay Islands in India chronically suffer from Al-toxicity (Chowdhury et al., 2001).

7.1. INTRODUCTION

Abiotic stress is a major limiting factor in crop productivity. Several stresses, such as high temperature, high light intensity, osmotic stress, heavy metals, and several herbicides and toxin lead to over production of reactive oxygen species (ROS), causing extensive cellular damage and inhibition of photosynthesis (Allen, 1997). ROS is produced in both unstressed and stressed cells. Plants have well developed mechanisms against ROS, involving both limiting the formation of ROS as well as instituting its removal. Under unstressed conditions, the formation and removal of O₂ are balance. Introduction of molecular oxygen (O₂) into atmosphere by O₂- evolving photosynthetic organisms, ROS has been the unwelcome companion of anaerobic metabolism. In contrast to O₂, these partially reduced or activated derivatives of oxygen (O₂¹, O2-, H₂O₂, and HO) are highly reactive and toxic and can lead to the oxidative destruction in tissues during stress.

6.1. INTRODUCTION

Low temperature is one of the major environmental factors that limit the plant growth. Many plants of tropical origin suffer cold damage when exposed to temperature below 20ºC (Graham and Patterson, 1982, Andrews, 1987). Cold temperature in crop plants are compounded by cold snap– a lower than usual drop in temperature that causes the crop to fail. Low temperature in growing season may reduce germination, retard vegetative growth by inducing metabolic imbalances and can delay or prevent productive development. Each plant species has an optimum range of temperature for its normal growth and development. It varies among the genotypes within a species, the specific temperature also depends on the growth stage and development of the particular genotype.

5.1. INTRODUCTION

Temperature is the one of the most important environmental element influencing the plant growth and development limiting the productivity and adaptation of crops, especially when it coincides with critical ranges (Chen et al., 1982; Paulsen, 1994). Nearly all commercial crops in the arid and semi-arid tropics often suffer from heat stress. Every plant has an optimal temperature for its normal growth, deviation from this may cause stress to plants. The adverse effects on plant of temperatures higher than the optimal considered as heat stress. Crops are exposed to periods of heat stress during their life-cycle. The optimum temperature for the most species ranges from 25 to 35 0C. Above this value, a decline in the photosynthesis rate is observed (Berry and Bjorkman, 1980; Pimentel, 1998). Even brief periods of heat-shock between temperature ranges of 45-50 0C induce marked change in plant growth processes.

4.1. INTRODUCTION

Water stress is the single most severe limitation to the productivity of rice in the rainfed ecosystem (Widawsky and O’Toole, 1990). Drought has been defined as the inadequacy of water availability, including precipitation and soil moisture storage capacity, in quantity and distribution during the life cycle of the crop to restrict expression of its full genetic yield potential. Drought is actually a meteorological event which implies the absence of rainfall for a period of time, long enough to cause moisture-depletion in soil and water deficit with a decrease of water potential in plant tissues. Under drought conditions, water stress develops in the plants as the demand exceeds supply of water; this may occur either/or both due to atmospheric or soil conditions, and is reflected in a gradient of water potentials developed between the soil or soil-root interface and leaf, the transpiring organ. Moisture stress is likely to develop to a different rate in different plant organs along with the gradient. Drought like many other environmental stresses has adverse effects on plant growth and yield.

3.1. INTRODUCTION 

Transitory waterlogging occurs extensively in both irrigated and dry land agriculture on clay flats and duplex soils. Most of the humid tropical lowlands, with adequate, rain-fed but poor drainage, have the problems of waterlogging, which is further intensified by low water table and poor root aeration. In submerged condition, only root is exposed to excess water and the injury to the shoot is not a primary effect.

The term ‘waterlogging’ is defined as a condition of the soil where excess water inhibits gas exchange of roots with the atmosphere. Waterlogging is different from ‘flooding’ because the latter results in addition factors of partial or complete submergence of the shoot. The waterlogging replaces a gaseous air by liquid water, leading to the gas stresses. Schematic representation of adverse effects of waterlogging on plant growth and survival has been given in Fig. 3.1.

2.1. INTRODUCTION

Salt stress has become an ever increasing threat to food production. It is a major factor limiting the crop productivity in the arid and semi-arid areas of the world (Ashraf, 1994; Foolad and Jones, 1992) and it affects about 10% of the total global land area (Richards, 1995). Increased salinization of arable lands is expected to have devastating global effects, resulting in 30% land losses within the next 25 years and up to 50% by the year 2050 (Wang et al., 2003).

Soluble salts can cause harm to plant, if they are in high concentration in water or soils and it limit crop cultivation world wide. Generally an array of stresses interplay in saline soils and reduces productivity of salt sensitive crops. In India, about 12 mha of land has been affected with salinity and alkalinity (Yadav and Gupta, 1984); an area of nearly 4 mha of land suitable for rice affected with salinity (Paul and Ghosh, 1986). The optimum salt concentration for the growth of halophytes is found to be about 0.5 M NaCl (Flower and Yeo, 1981). Most of the crop plants are salt sensitive glycophytes.