Agriculture Reference
In-Depth Information
A plant's ability to generate abundant energy becomes more
important when it is put under additional stress, such as cold
soil and air temperature.
Cold acclimatization of plants is a highly active process
resulting from the expression of a number of physiological and
metabolic adaptations to low temperature (Levitt 1980). Major
metabolic changes in carbohydrates, proteins, nucleic acids,
amino acids, and growth regulators have been documented
during the acquisition of cold tolerance. Among these, water
soluble carbohydrates like the fructose polymers and fructans
were shown to accumulate during cold acclimatization of
grass species (Pollock and Crains 1991, Livingston 1991).
Fructans are claimed to enhance the cold tolerance in plants.
The ability of plants to synthesize fructans correlates their
survival in colder climates. Relationship between cold tolerance
and fructan accumulation has been noted in cereals (Suzuki
and Nass 1988, Pontis 1989). Evidence suggests that soluble
sugars, such as sucrose and oligosaccharides of the raffi nose
family, in combination with heat stable proteins could play a
determinant role in cold stress tolerance by protecting proteins
and membranes against freeze-induced denaturation (Gusta
et al. 1996).
Cold stress induced major changes in amino acid levels
in wintering crowns of the three ecotypes and the highest
contributions to total amino acid accumulation after
acclimatization at low temperatures came from proline,
glutamine and glutaric acid. Heat stable proteins have been
isolated from cold acclimated plants and a correlation between
a heat stable protein accumulation and cold induced freezing
tolerance suggested that cold acclimatization induced proteins
may act in combination with soluble carbohydrates and
compounds in the acquisition of freezing tolerance (Gusta et
al. 1996).
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