Abstract
Exposure of plants to low temperature in the light may induce photoinhibitory stress symptoms, including oxidative damage. However, it is also known that light is a critical factor for the development of frost hardiness in cold tolerant plants. In the present work the effects of light during the cold acclimation period were studied in chilling-sensitive maize plants. Before exposure to chilling temperature at 5°C, plants were cold acclimated at non-lethal temperature (15°C) under different light conditions. Although exposure to relatively high light intensities during cold acclimation caused various stress symptoms, it also enhanced the effectiveness of acclimation processes to a subsequent severe cold stress. It seems that the photoinhibition induced by low temperature is a necessary evil for cold acclimation processes in plants. Greater accumulations of soluble sugars were also detected during hardening at relatively high light intensity. Certain stress responses were light-dependent not only in the leaves, but also in the roots. The comparison of the gene expression profiles based on a microarray study demonstrated that the light intensity is at least as important a factor as the temperature during the cold acclimation period. Differentially expressed genes were mainly involved in most of assimilation and metabolic pathways, namely photosynthetic light capture via the modification of chlorophyll biosynthesis and the dark reactions, carboxylic acid metabolism, cellular amino acid, porphyrin or glutathione metabolic processes, ribosome biogenesis and translation. Results revealed complex regulation mechanisms and interactions between cold and light signalling processes.
Highlights
Low temperature is one of the most important factors limiting the spread and production of plants worldwide
In the 1st set of experiments maize plants were grown at relatively low light intensity (GL1 = 180 μmol m−2 s−1), after which some plants were hardened at even lower light intensity (LL1 or low light intensity 2 (LL2)), followed by chilling stress under continuous illumination at growth light 1 (GL1)
Since it is possible for even chilling-sensitive maize plants to become acclimated to relatively low temperatures (Anderson et al, 1994; Janda et al, 1998), an analogous experiment was carried out to elucidate how light contributes to the development of cold acclimation processes in maize plants
Summary
Low temperature is one of the most important factors limiting the spread and production of plants worldwide. This is especially true for field crops of tropical or subtropical origin. In the case of chilling-sensitive maize plants, temperatures in the 10–15◦C range decrease the capacity for biomass production, while the exposure of plants to still lower temperatures for a prolonged period may lead to irreversible damage and the death of the plants (Bredenkamp and Baker, 1994; Greaves, 1996). Efficient early germination and growth at cool temperatures in the spring is a critical part of resistance to low temperature stress in young maize plants.
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