What Are Cgh Emissions

Mitchell et al. (1993)

* C, chamber; CEC, controlled-environment chamber; GC, growth chamber; FACE, free-air CO2 enrichment; GH, greenhouse; OTC, open-top chamber; SPAR, soil-plant-atmosphere-research unit.

* C, chamber; CEC, controlled-environment chamber; GC, growth chamber; FACE, free-air CO2 enrichment; GH, greenhouse; OTC, open-top chamber; SPAR, soil-plant-atmosphere-research unit.

developed (Kirschbaum 1994; Mitchell et al. 1995). Long (1991) postulated that elevated atmospheric CO2 concentration at higher temperatures would increase net CO2 assimilation and carbon pools, which facilitate dissipation of excess light energy resulting in decreased photoinhibition and thus leads to increased plant productivity. As shown in Table 1.1, a positive interaction between elevated CO2 and high temperature on photosynthesis of C3 plants has been reported by some investigators (Hakala 1998; Vu 2005; Borjigidai et al. 2006), but not by others (Mitchell et al. 1993; Prasad et al. 2005; Reddy et al. 2005).

Sionit et al. (1987) reported that under CO2 doubling, soybean yield was greater for plants grown under 26/20°C than for those grown under 22/16°C or 18/12°C of day/night temperature regimes. However, Prasad et al. (2002) showed that in kidney bean (Phaseolus vulgaris L.), elevated CO2 did not offset the detrimental effects of high temperatures on reproductive processes and yield. Also, no direct beneficial effects of elevated CO2 at high temperature was found in both heat-sensitive and heat-tolerant lines of cowpea (Ahmed et al. 1993). As stated by Reddy et al. (1996), CO2 enrichment and increased water and nutrients do not mitigate the adverse effects of the above-optimum temperatures on food and fiber production.

In response to elevated CO2 and high temperature, some researchers working on the same crop species have reported contradictory results (Table 1.1). These differences might be related to differences in experimental approaches, stage of crop development as well as other environmental factors, which probably have not been taken into consideration during the experiments.

Although elevation of atmospheric CO2 and air temperature are important components of global climate change, there are other factors, which are correlated with these two factors (Fig. 1.1). For instance, global warming is likely to affect precipitation patterns around the world in such a way that there will be severe drought condition in one region and flooding in another region (IPCC 2007). As an example, we consider the effects of three components of global climate change, such as CO2, temperature and drought, on canola growth and physiology (Table 1.2).

When drought was not considered as a factor, no differences were found in growth between plants grown under higher temperature at elevated CO2 and plants grown under lower temperature at ambient CO2, because elevated CO2 mitigated the adverse effects of high temperature in the first situation. However, drought stress plus elevated CO2 and higher temperature decreased growth, as did higher temperature at ambient CO2 concentration. Also, regardless of CO2 level, drought stress increased abscisic acid content, but higher temperature inhibited the ability of plants to produce abscisic acid in response to drought (Table 1.3). On the basis of this

Table 1.2 Growth and physiological responses of canola (Brassica napus) plants to elevated CO2 (eCO2), higher temperature (HT) and the combined effects of eCO2 and HT, and eCO2, HT and drought stress (DS), compared to the well-watered plants grown under lower temperature at ambient CO2 level

Crop response

eC02

Renewable Energy Eco Friendly

Renewable Energy Eco Friendly

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable.

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