Contents

1 Climate Change and Global Crop Productivity an Overview 1 Part II The Problem Changing Biosphere 2 Climatic Change and Variability 7 2.3 20th Century Climate 10 2.4 Role of Greenhouse Gases 12 2.5 Anthropogenic Aerosol Effects 17 2.6 Future Climate Change 18 2.7 The IPCC Third Assessment Report 27 2.8 Concluding Remarks 28 References 29 3 Agricultural Contributions to Greenhouse Gas Emissions 37 D C. Reicosky, JL . Hatfield and R.L. Sass 3.2 Fossil Fuel Use in Agriculture 39 3.3 Management of...

Role of Greenhouse Gases

The greenhouse effect is a natural feature of the climate system. In fact, without the atmosphere (and hence the greenhouse effect), the earth's average temperature would be approximately 33 C colder than it is currently. The earth atmosphere system balances absorption of solar radiation with emission of longwave (infrared) radiation to space. The earth's surface primarily absorbs most of the shortwave solar radiation from the sun, but it also reradiates some of this radiation as longwave...

Belowground tree responses to elevated [CO2

Whether or not the potential increase in plant growth under elevated CO2 is realized and will be sustained is a function of the nutrient and water availability and of the ability of plants to compete with soil biota for these resources. In elevated CO2 , plants generally increase their nutrient uptake capacity by allocating more C to their roots, resulting in higher fine-root densities and mycorrhizal colonization (Rogers et al., 1998). The subsequent increased below-ground C losses from root...

Effects of [CO2 Under Waterlimiting Conditions

Much of the global wheat production is water-limited and so the effect of GEC on water availability is crucial. While the effect of elevated CO2 on gs is fairly consistent (even for varieties which differ in gs Samarakoon et al., 1995), the effects on transpiration are complex (Lawlor, 1998). A lower rate of transpiration and less latent cooling increases the water vapour pressure in the intercellular spaces of the leaves, and decreases the humidity of the air in the boundary layer....

Crop Water Relations and Global Climate Change

The major effects of global climate change on crop water relations that are relevant to plant breeding are likely to occur due to changes in rainfall and soil drought for crops grown without irrigation. Where rainfall is reduced, breeding may have to give greater emphasis to enhancing adaptation to drought and this can be a difficult task (Blum, 1988 Eastin et al., 1988). In regions where global climate change substantially reduces rainfall, it may be necessary for farmers to grow alternative...

Conclusions

Of the global change effects discussed here, none is potentially more significant for rangelands than a shift in botanical composition. Yet species change is also among the most difficult of global change effects to predict, because it is highly context-specific at the spatial and temporal scales of field experiments. What is needed is a more systematic examination of the ways in which global changes interact with and modify the characteristics of plants that determine their responses to...

Contributors

G ran I. gren, Department of Ecology and Environmental Research, Swedish University of Agricultural Sciences, PO Box 7072, SE-750 Uppsala, Sweden Leon Hartwell Allen, Jr, USDA-Agricultural Research Service, Institute of Food and Agricultural Sciences, S.W. 23rd St., University of Florida, PO Box 110965, Gainesville, FL 32611-0965, USA Jeffery T. Baker, USDA-ARS NRI RSML, 10300 Baltimore Avenue, Beltsville, MD 20705-2350, USA Marco Bindi, Department of Agronomy and Land Management, University of...

Carbon dioxide

It has been known for a long time that the photosynthesis of single leaves of C3 species generally increases under elevated CO2 . This increase depends not only on CO2 , but also on light, temperature, nutrients, water, leaf age, etc. The daily average photosynthesis of young leaves increased by 30-80 at 60 Pa (600 ppm) compared with ambient (35 Pa) CO2 partial pressure in perennial ryegrass swards (Rogers et al., 1998). Drake et al. (1997) determined an average increase of 58 in photosynthesis...

Crop Yields

Cure (1985) summarized soybean seed yields from 12 elevated- CO2 experiments. Several of the studies were conducted with CO2 enrichment above 1000 mmol mol-1, and most yield responses were reported on a per plant rather than a land area basis. Also, several experiments were conducted in growth chambers rather than in sunlight. Nevertheless, the overall response for soybean was a yield increase of 29 8 from a doubling of CO2 . Rogers et al. (1986) summarized yield response ratios and changes in...

Introduction

The world today is faced with great challenges to produce adequate food, feed and industrial products for the globe's 6 billion people. Nearly 200 new residents are added to our planet every minute and approximately 80 million every year. Furthermore, the area of arable land available to feed this population is shrinking and is subject to significant loss of topsoil and ground-water. Future population growth will continue, most noticeably in developing nations. Closely linked with this...

Cultural and Breeding Strategies for Future Climate

Increasing CO2 will increase crop production potentials, but associated expected climatic changes may decrease potential production. Model predictions of soybean production in the southeastern USA were seriously impacted by both inadequate soil water (inadequate rainfall) and high temperatures (Curry et al., 1990a,b, 1995). When simulations employed optimum irrigation, yields were always improved by elevated CO2 . Irrigation is a cultural practice that could alleviate both inadequate rainfall...

Interactions

Temperature increases from global warming will occur simultaneously with CO2 increases, and the interaction has been suggested by a number of researchers (e.g. Idso et al., 1987) to be beneficial. In a number of species, the response of vegetative growth to CO2 enrichment increases with temperature (Boote et al., 1997 and references cited therein), presumably because the plants are better able to utilize additional carbohydrate when growth rates are more rapid and this minimizes downward...

Impacts on Forage Quality

Animal production on rangelands, as in other grazing systems, depends on the quality as well as the quantity of forage. Key quality parameters for rangeland forage include fibre content and concentrations of crude protein, non-structural carbohydrates, minerals and secondary toxic compounds. Ruminants require forage with about 7 crude protein (as a percentage of dietary dry matter) for maintenance, 10-14 protein for growth and 15 protein for lactation (Ulyatt et al., 1980). Optimal rumen...

Effects of [CO2 and temperature on respiration

Dark respiration is a major component of plant productivity. Approximately 50 of total assimilates acquired by photosynthesis are respired (Amthor, 1997). An unexpected feature of respiration to GEC is an apparent decrease in its rate when expressed per unit of dry matter. Such a decrease is often observed in plants grown in elevated CO2 (Poorter et at., 1992). Part, or all, of this decreased respiration is probably due to the decreased proportion of metabolic components per unit dry matter as...

References

Ankersmit, G.W. and Adkisson, P.L. (1968) Photoperiodic responses of certain geographic strains of Pectinophora gossypiella (Lepidoptera), Journal of Insect Physiology 13, 553-564. Batzli, G.O. (1974) Production assimilation and accumulation of organic matter in ecosystems. Journal of Theoretical Biology 45, 205-217. Berryman, A.A. and Gutierrez, A.P. (1998) Dynamics of insect predator-prey interactions. In Huffaker, C.B. and Gutierrez, A.P. (eds) Ecological Entomology, 2nd edn. John Wiley &...

Photosynthesis

Cotton canopies grown continuously in elevated CO2 responded to increasing solar radiation with increasing rates of photosynthesis (Fig. 8.1). Table 8.1. Treatment structures for experiments conducted on cotton in naturally sunlit environment chambers (SPAR units) for the last 10 years. Table 8.1. Treatment structures for experiments conducted on cotton in naturally sunlit environment chambers (SPAR units) for the last 10 years. 70 days from emergence, well-watered and fertilized (V.R....

Mitigation Options for Agriculture

What agriculture can do to mitigate GHG emissions has been estimated by Cole et al. (1997), whose estimates of potential reduction of radiative forcing by the agricultural sector range from 1150 to 3300 MMTCE year-1. Of the total potential global reduction in GHG emissions, approximately 32 could result from reduction in CO2 emissions, 42 of the C offsets from biofuel production on 15 of the existing croplands, 16 from reduced CH4 emissions and 10 from reduced emissions of N2O. Agriculture can...

Per Unit Mass Growth Dynamics

Suppose that each unit of herbivore mass (H) consumes fh units of resource mass (P), and that rh (respiration rate) units are required to sustain life, then fh - rh units will be available for growth and reproduction. The effects of temperature and levels of food on fh are illustrated in Figure 16.5a. Consumption (f) depends on temperature but also decreases with level of resource (the thinner lines). Also shown is the respiration rate rh (i.e. the Q10 rule), which increases with temperature...

Photosynthesis and respiration

Rice, being a C3 plant, responds very well to increased CO2 . Several long- and short-term CO2 enrichment studies show that doubling the current ambient CO2 increased leaf-level photosynthetic rate by 30-70 . The magnitude of this increase depended on the particular rice cultivar, growth stage and environment (Imai and Murata, 1978 Akita, 1980 Morrison and Gifford, 1983 Fig. 5.3. Schematic drawing of the temperature gradient chamber (TGC) for CO2 enrichment (bottom) and ambient CO2 (top)...

Productivity

Most productivity studies on agronomic C3 and C4 species were done before 1975 (Loomis and Gerakis, 1975). After that time, the focus has been on increasing their harvest index (fraction of the plant harvested), as well as on aspects of plant performance that can be affected by molecular biology biotechnology. Very little such attention has been devoted to CAM plants, although efforts to preserve the germplasm with field plantings in various countries have been made with prospects for increased...

Some Modelling Preliminaries

The question of how to model complex biological systems and how much detail to include in the model remains open. The debate is often couched in arguments about simple vs. complex models. Here the focus will be on physiologically based models of intermediate complexity (i.e. process models) that are driven by weather and influenced by various abiotic factors. For convenience, a simple food chain consisting of a plant (P), herbivore (H) and carnivore (C) is used to illustrate the issues. All of...

Potato

Short photoperiods (i.e. long nights) and cool temperatures induce tuber formation in potato (Ewing, 1997). Potato yields are particularly sensitive to high-temperature stress because tuber induction (Reynolds and Ewing, 1989 Gawronska et al., 1992) and development (Krauss and Marschner, 1984) can be directly inhibited by even moderately high temperatures. There is an interaction between photoperiod and temperature the higher the temperature, the shorter is the photoperiod required for...

Summary and Conclusions

Cotton crops grown in future environments will be subjected to projected climatic changes for which they were not bred. Our series of studies, using SPAR, OTC and FACE experimental technologies and facilities, provided detailed insight into how cotton will respond to a changing environment. We believe that several important conclusions regarding the effects of elevated CO2 , temperature, water and nutrients on plants can be drawn from our cotton experiments. The direct physiological effects of...

Nutrient deficits

While plants growing under limited N supply show reduced above-ground growth compared with non-limited plants, their root mass increased (Hebeisen etal., 1997) or decreased (Jongen etal., 1995 Soussana et al., 1996). However, the root shoot biomass ratio increased strongly (Soussana et al., 1996) i.e. a smaller proportion of total biomass was harvested. Leaf N and root N decreased, though the reduction in root N was much smaller. The larger proportion of root biomass implies that the roots...

Wheat Quality

Despite the great emphasis placed on quality of wheat for nutritional and industrial uses (Heyne, 1987), there is little understanding of the interaction between environmental and genetic factors determining composition of wheat grain under current conditions. Supply of nutrients, particularly N, determines (in conjunction with other factors such as water supply and temperature) protein amounts relative to starch and other non-N components. Nutrient supply thus alters N-concentration, but only...

Site scale

Simulated climatic change in northern Europe resulted in small to considerable increases in a mean tuber yield for both irrigated and non-irrigated potato crops (Fig. 9.10a,c). In central and southern Europe, climatic change resulted in both small decreases and increases in tuber yields for both irrigated and Fig. 9.10. Simulated potato tuber yields (mid variety) using NPOTATO. Present and future climate conditions at sites in northern (Jokioinen, Tylstrup and Oxford) and southern Europe...

Transpiration and Water

Water is the key variable that affects cotton production, since the crop is grown mostly in arid and semi-arid regions of the world under rain-fed conditions. Transpiration from individual leaves growing in high CO2 is usually lower than that from leaves growing in ambient CO2 (e.g. Kimball and Idso, 1983 K.R. Reddy et al., 1996b) because the elevated CO2 causes partial stomatal closure. Changes in stomatal density in herbarium samples collected over several centuries indicate that increasing...

Reproductive development

High temperature affects reproductive development in two ways, both of which potentially reduce yields. Firstly, the rate of reproductive development is accelerated, which shortens the seed-filling period and the fruit maturation period. Generally, this results in lower individual seed and fruit weights and in some cases reduced concentrations of soluble solids in the fruit. In addition, in many crops the reproductive events themselves are prevented at temperatures only a few degrees above...

Water deficits

The yield of perennial ryegrass under moderate drought stress increased by an average of 19 and 14 in low- and high-N swards, respectively, at elevated CO2 (Table 12.1) (Casella et al., 1996). In summer, when the water deficit was greater, elevated CO2 increased yield by 48 . In spring and autumn, the yield increased by only 6 . However, the effects of water deficit and temperature were confounded. At elevated CO2, a temperature increase of 3 C increased the water deficit in summer, due to...

Temperature

The temperature response of plant growth shows an optimum curve. At low temperature, elevated CO2 has no or only small effects, as indicated by the lack of increase in photosynthesis. At elevated CO2 , the annual yield of ryegrass did not change in response to a 3 C increase in temperature, but the root fraction of total biomass decreased (Casella et al., 1996). However, the yield increased in spring and autumn, when temperatures were suboptimal, and decreased in summer. The decline in the CO2...

Sourcesink relations and fruit production

Another major difference between trees and non-woody plants is their source-to-sink ratio. A sink is defined as the region of a plant that is a net consumer of carbohydrates a source is defined as the region of a plant that is a net producer of carbohydrates. The canopy, as a whole, is essentially viewed as source tissue therefore, pruning of tree canopies results in a reduced source activity. However, a new and rapidly developing canopy may also be viewed as sink tissue. Whereas photosynthesis...

Uniformity and variability in tree responses

In comparison with crop species, the response of tree species to CO2 enrichment is slightly less well understood. This is probably due to the large buffering effect of the woody storage compartments. However, the effects of elevated CO2 , and to a much lesser extent of temperature, on tree growth and physiology have been extensively examined and reviewed during the last decade. Reviews on above-ground responses (e.g. Eamus and Jarvis, 1989 Mousseau and Saugier, 1992 Ceulemans and Mousseau, 1994...

Effects of temperature extremes

Quite separate from the effects of temperature on wheat phenology are the effects of temperature extremes. Extreme cold may kill wheat, and late frost induces sterility (Russell and Wilson, 1994). Chilling temperatures (below 5 C) and hot temperatures (above 30 C) at anthesis can damage pollen formation, which in turn reduces grain set and can decrease yield (Dawson and Wardlaw, 1989 Tashiro and Wardlaw, 1990). There is a wide range of susceptibility to these effects among varieties. GEC will...

Raja Reddy and Harry F Hodges

Department of Plant and Soil Sciences, 117 Dorman Hall, Box 9555, Mississippi State University, Mississippi State, MS 39762, USA Weather is the most important cause of year-to-year variability in crop production, even in high-yield and high-technology environments. There has been considerable concern in recent years about the possibility of climatic changes caused by human activities, because any change in weather will increase uncertainty regarding food production. Since the beginning of the...

Crop Pest Relations and Global Climate Change

A major potential problem confronting farmers would be where global climate change results in the occurrence of much larger populations of troublesome insect pests in specific regions. In temperate and subtropical climates, the extent to which insect pest populations build up during the growing season can depend on how well the insect pests survive the winter and how fast their populations increase during the growing season. Relatively small increases in minimum temperatures during the winter...

Water

Carbon dioxide can influence water use of plants in two ways. Firstly, CO2 directly controls stomatal conductance through its control of stomatal aperture. In most crops, including soybean, stomata are partially closed by elevated CO2 . Morison (1987) analysed 80 sets of data and found that doubled CO2 decreased stomatal conductance of leaves by about 40 5 . On the other hand, CO2 can promote growth, and thus produce more leaf area that will increase the transpiring surface area per unit land...

Growth and Development Phenology

Elevated CO2 effects on soybean phenology appear to be small and not consistent. Allen et al. (1990a) summarized the effect of CO2 on soybean developmental stages for four experiments from 1981 to 1984. They fitted vegetative stage (V) vs. DAP to a linear regression equation as follows where 00 intercept of the regression on the V-stage axis and 01 mainstem nodes per day. In general, 01 increased slightly with increasing CO2 , but the responses among the four experiments were variable. The...

Growth and Development Growth Rates of Organs

Carbon dioxide affects the partitioning of dry matter to various plant organs. Acock and Allen (1985) summarized growth and development information for Table 7.6. Plastochron interval and final mainstem node number for soybean in CO2 and air temperature experiments in controlled-environment chambers. (Adapted from Baker et al, 1989.) Table 7.6. Plastochron interval and final mainstem node number for soybean in CO2 and air temperature experiments in controlled-environment chambers. (Adapted from...

Impacts on the Vegetable Industry

It is not clear whether the overall impact of global warming will be positive or negative relative to production of vegetable crops. In areas where mean daily temperatures do not currently exceed 25 C during the growing season, overall effects should be beneficial, while they may be negative where growing-season temperatures are higher. Higher temperatures should also be more beneficial in areas that currently have short growing seasons and most production in the summer, compared with areas...

Preface

Human activities are creating changes in our earth ecosystem. Emissions of carbon dioxide and other greenhouse gases are increasing. The evidence, using state-of-the-art computer models incorporating as much of the theoretical understanding of the earth's weather as possible, suggests that global warming is occurring along with shifting patterns of rainfall and incidences of extreme weather events. The rate of global climate change and warming expected over the next century is more than has...

Effects of [CO2 and temperature on crop development

It is difficult to disentangle with certainty direct (as CO2 per se) and indirect (temperature increases due to smaller gs) effects of CO2 on crop development. However, there is little evidence of any direct CO2 effect on the rate of development in wheat at any stage. Slightly faster rates of leaf, ear, spike and tiller development are frequently observed in wheat grown at elevated CO2 and are probably indirect. The complete absence of an effect of elevated CO2 on wheat phenology in conditions...

The Concept of Interaction

Some of the topics addressed by Krupa et al. (1998a) relate to the application of existing scientific knowledge of environment crop interactions to the global spatial grid for revealing patterns of their spatial variability at the present time. Other topics are more fundamental for understanding the dynamic relationships that occur at any spatial level, from global to the local scale. The contents of this chapter are in the latter context, without considering the spatial term. The focus is on...

Feedback to natural greenhouse gases water vapour

The most abundant greenhouse gas in the atmosphere is water vapour, but humans are not directly increasing its amount. However, it is anticipated that atmospheric increases in other greenhouse gases will lead to global warming, which will in turn lead to increased water vapour in the atmosphere because of increased evaporative capacity. Therefore, increase in water vapour is viewed as a feedback from the increases in the anthropogenically produced greenhouse gases CO2, CH4, N2O and CFCs, rather...

Transpiration and water use

Leaf-level transpiration rate (E, mmol m-2 s-1) can be expressed as E K e*(7L) - ej (ra + n) (Eqn 5.2) where K is a slightly temperature-dependent, physical constant for the conversion of vapour pressure (kPa) to gas concentration (mmol mol-1) e*(7L) is the saturation vapour pressure at leaf temperature, TL ea is the vapour pressure of air and ra and rs are the boundary layer and stomatal diffusive resistances of water vapour (mol m-2 s-1), respectively. A similar relationship to that shown in...

Plant Responses to Increases in Atmospheric [CO2

Substantial changes occurred in atmospheric CO2 in the geological past and in the 20th century (Allen, 1994). Millions of years ago, atmospheric CO2 was about 1200-4000 mol mol-1 but it decreased substantially over centuries (Sundquist, 1986). Analysis of air trapped in polar ice indicates that prior to 1800, atmospheric CO2 fluctuated between 180-290 mmol mol-1 for at least 220,000 years (Barnola et al., 1987 Jouzel et al., 1993). Since 1800, ice core data indicate accelerating increases in...

Management of Soil Carbon

Usa Midwest Soil

Conversion of forest land to agricultural land or urban use can result in changes in emissions of soil C as CO2. Conversely, net additions of forest and crop biomass can result in soil acting as a sink for CO2 (Raich and Potter, 1995). Agriculture and intensive tillage have caused a decrease of between 30 and 50 in soil C since many soils were brought into cultivation more than 100 years ago (Schlesinger, 1986 Houghton, 1995). There needs to be a better understanding of tillage processes, the...

Physical processes and current distributions

In recent years the potentially countervailing influence of aerosol forcing to increased greenhouse gas forcing on the atmosphere has become a new focus of attention (Wigley, 1989 Houghton et al., 1990). Aerosols are solid or liquid particles in the size range of 0.001 to 10 mm. Aerosols in the atmosphere influence the radiation balance of the earth directly, through scattering and absorption, and indirectly, by altering cloud properties. They affect the size, number and chemical composition of...

Comparative Responses of Crops and Weeds

15.2.1 Climatic change and photosynthetic pathway Almost all crop and weed species fall into two of the three major photo-synthetic pathways C3 and C4. Plants with the CAM pathway, such as pineapple and cacti, will not be discussed here (see Chapter 14, this volume). Numerous observations of the response of growth of C3 and C4 species to elevated CO2 support the expectation, discussed earlier, that C3 species are more responsive than C4 species. In a survey of responses of crop species, Kimball...

James A Bunce and Lewis H Ziska

Climate Stress Laboratory, USDA-ARS-BARC, B-046A, 10300 Baltimore Avenue, Beltsville, MD 20705-2350, USA 15.1 Introduction 15.1.1 The impact of weeds Plants have managed to occupy nearly all terrestrial habitats. Wherever humans attempt to reserve areas of land for the growth of directly useful species (crops), other species (weeds) grow there also. Because all plants use the same basic resources of light, minerals, water and carbon dioxide, and have the ability to disperse, the growing of crop...

Fossil Fuel Use in Agriculture

Energy is required for all agricultural operations. Modern intensive agriculture requires much more energy input than did traditional farming methods, since it relies on the use of fossil fuels for tillage, transportation and grain drying, for the manufacture of fertilizers, pesticides and equipment used as agricultural inputs, and for generating electricity used on farms (Frye, 1984). Early estimates suggested that fossil fuel usage by agriculture, primarily of liquid fuels and electricity,...

Growth and Development

As noted previously, there is uncertainty as to whether or not there is any direct effect of elevated pCO2 on photosynthetic carbon gain in C4 plants, but considerable evidence of a direct effect on respiration (Drake et al, 1999). There is still debate as to whether or not elevated CO2 directly enhances plant growth in C4 species. Increased growth under elevated pCO2 has been reported for a number of C4 species, including maize and sorghum (Wong, 1979 Poorter, 1993 Amthor et al., 1994)....

Impacts on Plant Species Composition

13.5.1 Importance of botanical composition Research has emphasized global change effects on plant and ecosystem production and water balance, but changes in plant species composition could have at least as great an impact on the goods and services that rangelands provide as might changes in production. Rangelands are used primarily for grazing. For most domestic herbivores, the preferred forage is grass. Other plants, including trees, shrubs, and other broadleaf species, can lessen livestock...

Values for Component Indices of Environmental Productivity Index

To determine the component indices of EPI (equation 14.1), plants are generally placed in environmental chambers, and one environmental factor is varied while the others are maintained at optimal values. Net CO2 uptake is then measured over 24 h periods. The only commercial CAM species for which the environmental indices relating to soil water status, temperature and PPF (equation 14.1) have been fully determined are A. fourcroydes, O. ficus-indica and S. queretaroensis partial results are...

Historical Trends Cotton Yields [CO2 and other Technological Advances

Cotton Lint Yield Per Acre

Historical US cotton yields (USDA, 1998) are presented in Fig. 8.12 along with changes in CO2 (Friedli et al., 1986 Keeling and Whorf, 1998). There has not been any attempt to relate long-term yield responses to temperatures because temperature data are much more complex. Cotton yields prior to 1940 were approximately 200 kg ha-1 and remarkably stable from year to year. Yields began to increase by about 1940 and reached 800 kg ha-1 in the mid-1990s. Numerous changes in technology occurred...

Nitrous Oxide and Methane Emissions from Animal Wastes and Lagoons

Nitrous oxide is produced from a wide variety of biological sources in soil, water, and animal wastes. During the last two centuries, human activities have increased N2O concentration by 13 (EPA, 1998). The main activities producing N2O are fossil fuel combustion, agricultural soil management and industrial sources. Use of large amounts of N fertilizer creates secondary problems associated with N2O released in anaerobic conditions (Mosier et al., 1998a). Agricultural soil management activities...

References Of Crop Physiology

Jr (1985) Crop responses to elevated carbon dioxide concentration. In Strain, B.R. and Cure, J.D. (eds) Direct Effects of Increasing Carbon Dioxide on Vegetation. US Department of Energy, Carbon Dioxide Research Division, DOE ER-0238, Washington, DC, pp. 53-97. Acock, B., Reddy, V.R., Hodges, H.F., Baker, D.N. and McKinion, J.M. (1985) Photosynthetic responses of soybean canopies to full-season carbon dioxide enrichment. Agronomy Journal 77, 942-947. Allen, L.H. Jr...

Introduction and Background

The best known crassulacean acid metabolism (CAM) crop species is the bromeliad pineapple (Ananas comosus), which is cultivated for its fruit on 720,000 ha in about 40 countries (Table 14.1 Bartholomew and Rohrbach, 1993). However, another CAM species (Opuntia ficus-indica), referred to as prickly pear, prickly pear cactus, cactus pear and nopal, is cultivated on just over 1 Mha in about 30 countries (Table 14.1 Russell and Felker, 1987 Nobel, 1996a Mizrahi et al, 1997). Most such cultivation...

Biotechnology and Abiotic Stresses

Plant Heavy Metal Mechanism

Recent advances in plant and microbial genomics have provided new and exciting molecular tools that allow scientists to dissect the biochemical and molecular mechanisms of stress tolerance or resistance. This information can be utilized to develop new crop plants that are protected from the impact of abiotic stresses. Since many of these major abiotic stresses arise as a result of a common biochemical phenomenon, efforts to improve tolerance to one Fig. 20.1. Mechanisms of plant response or...