Agriculture Reference
In-Depth Information
(Leon and Sheen 2003). A high glucose concentration leads to
high concentrations of ABA within cells (Arenas-Huertero et
al. 2000) and provides increasing gene transcription of ABA
biosynthesis (Cheng et al. 2002). In addition, sucrose, like
glucose is also necessary for the regulation of ABA biosynthesis.
Cytokinins are often considered abscisic acid antagonists and
auxins antagonists/synergists in various processes in plants
(Table 13).
Low temperature stress caused significant increase in
ascorbate (total, oxide and reduced) and a tocopherol levels in
both roots and leaves. Both roots and leaves of cold tolerant
variety IRCTN 33, ascorbate oxide was signifi cantly higher than
other varieties. Leaf hydrogen peroxide in sensitive variety,
Hoveizeh had signifi cantly increased, which had negative
correlation with the amount of chlorophylls. Significant
increase of malondialdehyde in Hoveizeh leaves showed
severe membrane phospholipid peroxidation. In the leaves the
least amount of H
2
O
2
was observed in cold tolerant genotype
IRCTN34. The roots ascorbate oxide form in IRCTN34 was
signifi cantly less than other genotypes.
However, Hoveizeh had weak antioxidant mechanism
among studied genotypes, while that of low temperature
tolerant genotypes were highly effi cient. Therefore, it is possible
to recommend them as tolerant parent for rice low temperature
breeding (Hassibi 2010).
Both biotic and abiotic stresses can result in oxidative
stress through the formation of free radicals, which are highly
destructive to lipids, nucleic acids, and proteins (Mittler 2002).
Water stress, which is also produced as a secondary stress by
chilling (Levitt 1980).
