Many definitions of food security exist, and these have been the subject of much debate. As early as 1992, Maxwell and Smith (1992) reviewed more than 180 items discussing concepts and definitions, and more definitions have been formulated since (DEFRA, 2006). Whereas many earlier definitions centered on food production, more recent definitions highlight access to food, in keeping with the 1996 World Food Summit definition (FAO, 1996) that food security is met when “all people, at all times, have physical and economic access to sufficient, safe, and nutritious food to meet their dietary needs and food preferences for an active and healthy life.” Worldwide attention on food access was given impetus by the food “price spike” in 2007–2008, triggered by a complex set of long- and short-term factors (FAO, 2009b; von Braun and Torero, 2009). FAO concluded, “provisional estimates show that, in 2007, 75 million more people were added to the total number of undernourished relative to 2003–05” (FAO, 2008); this is arguably a low-end estimate (Headey and Fan, 2010). More than enough food is currently produced per capita to feed the global population, yet about 870 million people remained hungry in the period from 2010 to 2012 (FAO et al., 2012). The questions for this chapter are how far climate and its change affect current food production systems and food security and the extent to which they will do so in the future (Figure 7-1).

Food security and food production systems

Phytoremediation: Environmentally sustainable way for reclamation of heavy metal polluted soils.

Folin phenol Reagentの呈色反応について-続-

Currently, food security depends on the increased production of cereals such as wheat (Triticum aestivum L.), which is an important source of calories and protein for humans. However, cells of the crop have suffered from the accumulation of reactive oxygen species (ROS), which can cause severe oxidative damage to the plants, due to environmental stresses. ROS are toxic molecules found in various subcellular compartments. The equilibrium between the production and detoxification of ROS is sustained by enzymatic and nonenzymatic antioxidants. In the present review, we offer a brief summary of antioxidant defense and hydrogen peroxide (H2O2) signaling in wheat plants. Wheat plants increase antioxidant defense mechanisms under abiotic stresses, such as drought, cold, heat, salinity and UV-B radiation, to alleviate oxidative damage. Moreover, H2O2 signaling is an important factor contributing to stress tolerance in cereals.

/pdf/antioxidant-responses-of-wheat-plants-under-stress-2293932w9r.pdf

Antioxidant responses of wheat plants under stress

http://www.indiaenvironmentportal.org.in/files/A%20comparison%20of%20North%20American%20and%20Asian%20exposure.pdf

A comparison of North American and Asian exposure-response data for ozone effects on crop yields.

Threat to food security under current levels of ground level ozone: A case study for Indian cultivars of rice

Heavy metal pollution is one of the major environmental problems which is caused by unchecked and uncontrolled discharge of hazardous chemicals consisting of heavy metals. Heavy metals affect agricultural land and plant’s productivity by affecting its most vital process, i.e., photosynthesis. Exposure of plants to heavy metals leads to generation of ROS, and few heavy metals are directly involved in electron transport. It also leads to lipid peroxidation destroying plant’s cell membrane and its associated organelles. Chlorophyll biosynthesis is affected by heavy metals as it substitutes Mg ion from chlorophyll. Few heavy metals also affect enzyme involved in chlorophyll biosynthesis as well as disturb electron transport in light reactions and affect various enzymes in dark reactions. This detailed information helps us to understand the mechanism linked with the impact of heavy metals on physiological responses affecting plant biomass and productivity which is of concern for agriculture. Therefore, the present chapter consists of whole information regarding the impact of heavy metals on photosynthetic pigments, photosynthetic apparatus, and light and dark reactions.

Impact of Heavy Metals on Physiological Processes of Plants: With Special Reference to Photosynthetic System

The effects of elevated CO2 and O3, singly and in combination were investigated on various physiological, biochemical and yield parameters of two locally grown wheat (Triticum aestivum L.) cultivars (HUW-37 and K-9107) in open top chambers (OTCs). Elevated CO2 stimulated photosynthetic rate (Ps) and Fv/Fm ratio and reduced the stomatal conductance (gs). Reactive oxygen species, lipid peroxidation, anti-oxidative enzymes, ascorbic acid and total phenolics were higher, whereas Ps, gs, Fv/Fm, protein and photosynthetic pigments were reduced in elevated O3 exposure, as compared to their controls. Under elevated CO2 + O3, elevated levels of CO2 modified the plant performance against O3 in both the cultivars. Elevated CO2 caused significant increase in economic yield. Exposure to elevated O3 caused significant reduction in yield and the effect was cultivar-specific. The study concluded that elevated CO2 ameliorated the negative impact of elevated O3 and cultivar HUW-37 was more sensitive to elevated O3 than K-9107.

http://nopr.niscair.res.in/bitstream/123456789/17098/1/IJBB%2050%282%29%20139-149.pdf

Individual and interactive effects of elevated carbon dioxide and ozone on tropical wheat (Triticum aestivum L.) cultivars with special emphasis on ROS generation and activation of antioxidant defence system.

ROS production and its detoxification in early and late sown cultivars of wheat under future O3 concentration.

Tropospheric ozone (O3) is the most important regional atmospheric pollutant causing risk to food production across the globe due to its phytotoxicity and prevalence over agricultural areas. Peak O3 concentrations have declined in Europe and North America due to reductions in precursors during the last decades, however, emissions of O3 precursors have increased in Asia. The current critical level of ozone is determined by the threshold for yield loss which is based on the seasonal sum of the external concentration above 40 ppb. In the present article, the impact of tropospheric O3 on crop photosynthesis, defense mechanism, growth, reproductive processes and yield of crop plants have been documented. O3 upon its entry into the leaf intercellular spaces rapidly forms reactive oxygen species and reacts with components of the leaf apoplast to initiate a complex set of responses that constitute variable countermeasures by antioxidative enzymes. Ozone affects photosynthetic process by influencing photosynthetic pigments, chlorophyll fluorescence kinetics and electron transport as well as carbon fixation in terms of decreased Rubisco activity and quantity. Translocation and allocation pattern of photosynthate also get influenced under O3, which affect reproductive processes and yield of crops. Plant species and cultivars exhibit a range of sensitivity to O3, which is identifiable in terms of biochemical, physiological, molecular and yield responses. Hence, understanding of cultivar sensitivity in context to O3 would be helpful in development of potential O3 biomarkers and O3 tolerant variables.

Richa Rai

Papers

Threat to food security under current levels of ground level ozone: A case study for Indian cultivars of rice

Impact of Heavy Metals on Physiological Processes of Plants: With Special Reference to Photosynthetic System

Individual and interactive effects of elevated carbon dioxide and ozone on tropical wheat (Triticum aestivum L.) cultivars with special emphasis on ROS generation and activation of antioxidant defence system.

ROS production and its detoxification in early and late sown cultivars of wheat under future O3 concentration.

Impact of Tropospheric Ozone on Crop Plants