Agriculture Reference
In-Depth Information
evapotranspiration indices could lower or deplete the water reservoir in
soils, creating water stress in plants during dry seasons. For example, wa-
ter stress is of great concern in fruit production, because trees are not ir-
rigated in many production areas around the world. It is well documented
that water stress not only reduces crop productivity but also tends to ac-
celerate fruit ripening (Henson, 2008). Other investigators forecast for the
near future that rising air temperature could induce more frequent occur-
rence of extreme drought, flooding or heat waves than in the past (Assad
et al., 2004).
Carbon dioxide (CO
2
), also known as the most important greenhouse
gas, and ozone (O
3
) concentrations in the atmosphere are changing during
the last decade and are affecting many aspects of fruit and vegetable crops
production around the globe (Felzer et al., 2007; Lloyd and Farquhar,
2008). Carbon dioxide concentrations are increasing in the atmosphere
during the last decades (Mearns, 2000). The current atmospheric CO
2
con-
centration is higher than at any time in the past 420,000 years (Petit et al.,
1999). Exposure to elevated temperatures can cause morphological, ana-
tomical, physiological, and, ultimately, biochemical changes in plant tis-
sues and, as a consequence, can affect growth and development of differ-
ent plant organs. These events can cause drastic reductions in commercial
yield. However, by understanding plant tissues physiological response to
high temperatures, mechanisms of heat tolerances and possible strategies
to improve yield, it is possible to predict reactions that will take place in
the different steps of fruit and vegetable crops production, harvest and
postharvest (Kays, 1997).
In citrus, climate risk is mainly influenced by temperature in addition
to elevated CO
2
. Woolf and Ferguson (2000) reported that the high tem-
peratures, both in terms of diurnal fluctuations and long-term exposure,
can result in differences in internal quality properties such as sugar con-
tents, tissue firmness, and oil levels. Singh
et al. (1998) found that the Kin-
now fruit showed sigmoid curve with three distinct phases from 15th May
to 15th July; 15th August to 15th November and 29th November to 8th
February. The TSS content as sugars increased while juice acid decreased
during the entire period of fruit growth, whereas ascorbic acid increased
initially and decreased with the advancement of the fruits development
distinctly in subtropical climatic condition. Tao et al. (2003) elaborated the
effect of light as environmental signal on stimulating carotenoid synthesis,
especially the accumulation of β-cryptoxanthin in citrus fruit peel. Other
