eChapters

1.0 INTRODUCTION

Cardamom (Elettaria cardamomum Maton.) acclaimed as the ‘Queen of Spices’ is the true cardamom belonging to the family Zingiberaceae. The cardamom of commerce is the dried ripe fruit and is one of the most important valued spices next only to saffron. It is native of evergreen forests of Western Ghats of South India. Cardamom is a shade loving plant (Pseophyte) thriving well in elevations up to 600-1200 m above MSL under an average annual rainfall of 1500-4000 mm and temperature range of 10-350C. India has been the world’s largest producer of cardamom until 1979-80. Later, Guatemala emerged as world’s premier producer and the exporter of cardamom accounting for about 90 per cent of the global trade. Cardamom is also grown lesser extent in Sri Lanka, Papua New Guinea and Tanzania.

1.0 INTRODUCTION

Black pepper popularly known as ‘King of spices’ or ‘Black gold’ is one of the important and earliest known spices produced and exported from India. Its original home is the dense evergreen forests of Western Ghats in south India. The flavour and fragrance of this oriental spice had a magic spell in human civilization and culture since very ancient days. Expeditions in search of pepper led to the discovery of new trade routes.

1.0 INTRODUCTION

The bacteria in the genus Ralstonia, Xanthomonas, Agrobacterium, Xylella, Pantoea, Leifsonia, Curtobacterium, Enterobactor, Pseudomonas, Corynebacterium, Erwinia cause the most important bacterial diseases of crop plants. Few of them are directly responsible for post harvests losses during storage or transit and many of them are known to cause disease in the field. These diseases are economically important due their potential to cause crop failure in crops including spice crops. Among the bacteria genus Ralstonia is very important owing to its broad host range across the plant kingdom. Traditionally bacterial diseases of crops are prevented by the principle of ‘Disease Avoidance’ rather than disease control in the field. Their fast rate of multiplication, selective host and rapid spread in the field makes the disease control one of the challenges in the production system. The organic strategies are very well fit in the disease avoidance in the field. The preemptive strategies works exceedingly well for management of bacterial disease in any crop. Few genus such as Ralstonia, Enterobacter and Xanthomonas have been frequented in spice crops.

1.0 INTRODUCTION

“Biological control is the reduction of the amount of inoculum or disease producing activity of a pathogen  or parasite  in its active or dormant state, by one or more organisms, accomplished naturally or through manipulation of the environment, host or antagonist or by mass introduction of one or more antagonists ” (Baker & Cook 1974). The biological world is a vast interacting network of living organisms in a state of dynamic equilibrium, reflecting changes in their physical environment and their relations to each other. Organisms exhibit many type of interactions in the process of achieving biological balance.  An organism may exert no effect on another or it may stimulate or inhibit the growth or development of the associate, it may stimulate or inhibit the formation of resting spores of the associate or it may enforce dormancy or cause lysis of the associate (Cooke & Baker, 1983).

1.0 INTRODUCTION

Infestation by insect pests is a major factor responsible for the low productivity of spice crops in India. Spice crops such as black pepper (Piper nigrum L.), cardamom (Elettaria cardamomum Maton), ginger (Zingiber officinale Roscoe) and turmeric (Curcuma longa L.) are infested by many species of insect pests, some of which cause severe crop losses. Adoption of integrated pest management (IPM) schedules in which biological control forms a major component is more relevant in these crops since excessive use of insecticides could lead to pesticide residues in the produce and other ecological hazards. Spices are high-value and export-oriented in nature and pesticide residues are the most important non-tariff barriers on trade in these produces. There has been a renewed interest during the past decade in developing environment–friendly crop management schedules in sustainable agriculture including spice crops, reflecting the increasing concern over pesticide misuse.

1.0. INTRODUCTION

The plant nutrient cycling depends on micro organisms that constitute major components of the biosphere. Although less than one per cent is cultured, a tremendous diversity exists in their populations. Transformation of nutrients from soil to plants is brought about by soil microorganisms. Latest molecular techniques enable scientists to understand and appreciate the diversity and help to utilize the beneficial effects of microbial diversity for increased productivity. Among soil organisms intense activity is found in and around rhizosphere of plants because of the presence of the secreted nutrients such as carbohydrates, amino acids and other cellular components present at the growing tip of roots. These root colonizing micro organism form symbiotic, associative, or parasitic relationship with the plants. These organisms have evolved mechanisms to occupy and reside in the specialized niche. These mechanisms are often utilized both for growth enhancement and disease suppression. The host also plays an important role in selecting its own microflora for the rhizosphere similar to the probiotic microflora of human gastrointestinal tract (Haas and Keel 2003).

1.0 INTRODUCTION

Soil fertility can be considered to be a measure of the soil’s ability to sustain satisfactory crop growth, both in the short and longer-term. Organic farming recognizes the soil as being central to a sustainable farming system. It could be argued that organically managed soils require a higher level of baseline fertility because shortfalls cannot be made up by applications of soluble fertilizers. Soil fertility is determined by a set of interactions between the physical and chemical environments of the system and by biological activity. Organic matter is linked intrinsically to soil fertility, because it is important in maintaining good soil physical conditions (e.g. soil structure, aeration and water holding capacity) and is an important nutrient reserve. Organic matter contains most of the soil reserve of N and large proportions of other nutrients such as phosphorus and sulphur.

1.1 Spice – definition and uses

Spice is defined as “a strongly flavoured or aromatic substance of vegetable origin, obtained from tropical plants, commonly used as a condiment”. A spice is a dried seed, fruit, root, rhizome, bark or vegetative substance or flower bud used in nutritionally insignificant quantities as a food additive for the purpose of flavoring. Spices are distinguished from herbs, which are leafy, green plant parts used for flavoring purposes. Herbs, such as basil or oregano, may be used fresh, and are commonly chopped into smaller pieces; spices, however, are dried and usually ground into a powder (http://www.reference.com/browse/wiki/Spice). American Spice Trade Association (ASTA) defines spices as “any dried plant product used primarily for seasoning purposes”. Included are tropical aromatics (pepper, cinnamon, cloves, etc.), leafy herbs (basil, oregano, marjoram, etc.), spice seeds (sesame, poppy, mustard, etc.) and dehydrated vegetables (onions, garlic, etc.) (http://www.astaspice.org/spice/frame_spice.htm). Many spices have other uses like food preservation, medicine, religious rituals, cosmetics, and perfumery or as vegetables.

Abstract

Nitrogen is the most limiting nutrient controlling production of all agricultural systems. Application of N fertilizer has increased food production tremendously all over the world. However, it also contributes towards global warming and ozone layer depletion through emission of nitrous oxide, a greenhouse gas (GHG). Therefore, there is a need to assess the possibilities of N management for climate change abatement and food security enhancement, while minimizing environmental and human health impacts. In this chapter, role of gaseous-N emission on N use and various mitigation options for Indian agriculture have been discussed. For the base year 2007, the direct and indirect N₂O emissions from Indian agricultural soils was estimated to be 136.29 Gg (35.3 Tg CO₂ equivalent) and 30.61 Gg (5.8 Tg CO₂ equivalent), respectively.

Abstract

Increases in atmospheric concentrations of CO₂ are likely to have major physiological consequences for plants, due to the major effects of atmospheric CO₂ on photosynthetic rates and the centrality of photosynthesis to plant metabolism. We review what is known about the effects of growth at elevated levels of CO₂ on the protein and N concentrations of plants in general, and food crops in particular. Growth at elevated CO₂ typically reduces plant tissue N concentrations by 10-15%. The physiological mechanisms behind this decrease in tissue protein and N are likely complex, and include both dilution from increased tissue concentrations of non-structural carbohydrates and decreased root uptake of N.

Abstract

During the past five decades, the role of nitrogen (N) fertilizer in augmenting foodgrain production has widely been recognized the world over. In Indian soils, N deficiency is recognized as a universal problem and its consumption has increased by more than 300 times during the last 60 years.

Abstract

Intensification of agriculture during the last few decades has resulted in considerable depletion of the productivity of Indian soils and the balance sheet of potassium (K) is highly negative due to very low level of K fertilization. Although the need for balanced fertilization is known for many years, it is not always observed in practice by farmers. Since the effects of nitrogen are easily seen and crops look more vigorous and yield better, excessive use of nitrogenous fertilizers, accompanied by an inadequate supply of other nutrients, is considered by farmers as a reasonable insurance against yield losses. Often, the lack of K restricts nitrogen uptake and utilization, and hence plant growth. When K is limiting, nitrogen fertilizers are used inefficiently by the plants. This nutrient imbalance is thus closely associated with low nitrogen-use-efficiency (NUE) of crop plants, which is detrimental to crop production and environment – because of the consequences of N unused by the crop.

Abstract

The abiotic stresses viz. drought, high temperature, water stress, salinity, heavy metal contaminations etc. cause variable effect on nitrogen (N) mineralization, its uptake and transport, assimilation and remobilization, and subsequently the growth and productivity of plants. The affect is generally negative, however, the magnitude of decrease in various processes is dependent on genotype, age of the plant, tissue under investigation, type and extent of the stress and other agro-climatic conditions. Biological nitrogen fixation and nitrate assimilation appear to be more sensitive than the ammonium assimilation possibly because re-assimilation of ammonia released in the tissue due to catabolism of N molecules is essential for the survival of plants. In addition, synthesis of stress metabolites (proline, glycine betaine and poly amines) is directly dependent on the availability of primary amino acid, glutamic acid. There are few well coordinated and detailed studies, determining the key factors involved in regulating NUE under abiotic stresses.

Abstract

Nitrogen is the most essential nutrient for all plants and is also the major limiting factor in plant productivity. High yielding varieties of all crops are responsive to nitrogen but its ever-increasing use has shown detrimental impact on the environment along with extremely low use efficiency. Nitrogen use efficiency (NUE) in crop plants depends on various internal and external factors, which are dealt in detail. There has been a significant interest in genetic engineering of the crops to improve NUE. The use of biotechnological interventions by manipulating genes of the nitrogen utilization pathway to improve NUE has not been very successful. But transgenics/mutants with modified capacities for nitrate uptake, assimilation and remobilization have enhanced our understanding of the genetic control of NUE. In both cellular, and at whole plant level the mechanisms involved in N remobilization from the senescing organs towards the grain have recently gained importance but their understanding is still preliminary. Recent evidences have shown that grain filling during later stages of crop growth is supported by N recycling.

Abstract

Nitrogen is the most important element in terms of nutrition for plants, nitrate being the most preferred form. Nitrate not only acts as nutritional element but also as a signal to modulate metabolism and plant architecture. Nitrate sensing mostly happens in the root tip through a hitherto unknown mechanism, but its response can be demonstrated on an organism-wide scale. Functional genomic studies revealed over a thousand nitrate-responsive genes, involved not only in N and C metabolism, but also in various other physio-logical processes. Identification of nitrate response element/s common to all these genes could pave the way to unravel the mechanism of nitrate signaling, but findings in this direction have remained inconclusive so far. Several trans-acting factors have been implicated in N signaling and response, but none of these have been convincingly demonstrated to be specific to this response. Nitrate uptake, which is sometimes associated with nitrate sensing, is also highly regulated process and involves multiple transport systems like HATS, LATS and dual affinity transporters.

Abstract

Nitrate reductase (NR) catalyzes the reduction of nitrate to nitrite, which is the first step in the nitrate assimilation pathway, but can also reduce nitrite to nitric oxide (NO), an important signaling molecule that is thought to mediate a wide array of developmental and physiological processes in plants. Accordingly, the amount of NR protein and its catalytic activity are closely controlled in the cell. This chapter focuses on the posttranslational regulation of NR activity, which has been known for some time to involve reversible protein phosphorylation. The hinge 1 region of NR contains the serine-534 regulatory site, which when phosphorylated can bind a 14-3-3 protein resulting in inhibition of NR activity. This fundamental mechanism underlies the rapid modulation of NR activity in leaves in response to light/dark transitions, and the activation of NR that occurs in response to hypoxia (e.g., as with soil flooding). Recent results suggest that the basis for hypoxia-induced NR activation, which is thought to be essential for plant survival, may involve reactive oxygen species (ROS), such as H₂O₂, that are produced in response to many plant stressors including hypoxia.

Abstract

Nitrate uptake from the soil is the first step in nitrate acquisition and utilization by plants. Nitrate uptake and its release into cells is mediated by nitrate transporter(s) located into the plasma membrane of the root. Three transporters have been identified by kinetic measurements in plant roots. These are constitutive high affinity nitrate transporter (cHATS), inducible high affinity nitrate transporter (iHATS) and low affinity nitrate transporter (LATS). Two of these display saturable kinetics; a low capacity constitutive system and a high capacity inducible system. In addition, a non-saturating low affinity, high capacity system becomes apparent only at higher external NO^-₃ concentration. Genes that encode representatives of each class of transport system have been identified and fall into two families: NRT1 and NRT2. Members of these families are induced in response to nitrate in the environment and are regulated by internal signals including nitrogen metabolites and shoot demand for nitrogen. This chapter deals with the physiology and molecular biology of nitrate transporters in higher plants.

Introduction

Engineered nanoparticles are a group of products that are defined by their size, ranging from 1 to 100 nm. Due to the smaller size, the physio-chemical properties of nano particles become very different from those of the same material in a larger form. Total production of nano-materials is expected to increase considerably in the near future. Nanotoxicology is yet another emerging field of science dealing with the effects of nano-devices and engineered nano-particles on living organisms. It has been observed that the materials in nano-dimensions react totally different in comparison to their existence in micro or macro sizes.

Introduction

The characterization of the potential health impact of engineered materials produced through nanotechnology is an emerging issue of considerable discussion and debate. The current focus on nanotoxicity fails to assess the risk in different local environments and populations. People in developing countries may be more prone to adverse effects of nanoparticles because of underlying health conditions and malnutrition. Moreover, genetic susceptibility to toxic effects varies in diverse ethnic groups and geographical areas. The scientific community needs to identify these information gaps before developing regulations and standard methodologies for nanotoxicity assessment.

Introduction
 
Nanotoxicity is a serious concern to be addressed sooner than later as nano-based processes and products in various fields are being extensively exploited. Nanotoxicology is the science of engineered nanodevices and nanostructures that deals with their effects in living organisms (Oberdorster et al., 2005). The unique property of nanoparticles is in its very large surface area to mass ratio, which is considered to be a boon to create novel products. But this distinctive property also challenges the way we identify, understand and address potential risks caused by nanoparticles (Rajkishore et al., 2011). It is sufficient to alert us to the fact that some engineered nanoparticles do indeed behave differently to their more conventional counterparts and may present new and unusual risks. Kahru and Dubourguier (2010) assessed the existing literature on nanotoxicity to main food chain levels (bacteria, algae, crustaceans, ciliates, fish, yeasts and nematodes) and classified the NPs of Ag and ZnO as “extremely toxic”, C60 fullerenes and CuO NP as “very toxic”, SWCNTs and MWCNTs as “toxic” and TiO₂ NP as “harmful”.