References

Jr, Boote, K.J., Jones, J.W., Jones, P.H., Valle, R.R., Acock, B., Rogers, H.H. and Dahlman, R.C. (1987) Response of vegetation to rising carbon dioxide photosynthesis, biomass, and seed yield of soybean. Global Biogeochemical Cycles 1, 1-14. Barrett, D. and Gifford, R.M. (1995) Photosynthetic acclimation to elevated CO2 in relation to biomass allocation in cotton. Journal of Biogeography 22, 331-339. Bos, E., Vu, M.Y., Massiah, E. and Bulatao, R.A. (1995) World Population...

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,...

Water

In theory, C4 species should require less water per gram of carbon assimilation than equivalent C3 species within the same environment. In leaves, water vapour passes from the mesophyll cell wall surface through the internal air space, stomata, leaf and canopy boundary layers to the bulk atmosphere through the same pathway as the photosynthetic pCO2 influx. Therefore, both gases are subject to the same diffusive limitations. The primary carboxylase in maize and sorghum, PEPc, is pCO2-saturated...

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

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

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...