ANTHOCYANINS UNDER DROUGHT AND DROUGHT-RELATED STRESSES IN BILBERRY (VACCINIUM MYRTILLUS L.), ACTA UNIVERSITATIS OULUENSIS A Sci e n t i a e Rerum Nat u r a l i u m 556

The aim was to study the effects of drought and indirect drought-related stresses on anthocyanin\ncontent in bilberry (Vaccinium myrtillus L.). Anthocyanin content was also studied in relation to\ndevelopmental stage (juvenile vs. mature leaves, previous vs. current-year stems). It was\nhypothesised that drought-stressed plants accumulate anthocyanins, but their direct role in osmotic\nregulation was questioned.\nDirect drought was created by preventing water supply. Freezing-induced dehydration was\naccomplished by removal of snow. Effects of summertime chilling (+2 °C during active growth,\n+5/0 °C during frost hardening) on water status were tested. The trace metal Nickel (Ni) was\napplied to the soil, as Ni may interfere with plant water relations at the rhizospheric level. Salt\n(Na+) was added to the soil to observe salt-induced disturbance in osmotic balance and ion\nhomeostasis.\nTissue water content (TWC) decreased and anthocyanin level increased under direct drought,\nespecially in the mature leaves. The freezing-stressed plants contained the same TWC and\nanthocyanin levels in mid-winter compared to plants that overwintered below snow. The freezingstressed\nplants had lower TWC and a similar anthocyanin level in early spring, and lower TWC\nand anthocyanin level in late spring than plants that overwintered below snow. In the summer and\nautumn following snow removal, current-year stems of freezing-stressed plants had the same\nTWC, but higher levels of anthocyanins than current-year stems of plants that overwintered below\nsnow. New growth was thus affected by the freezing stress experienced by previous-year stems.\nChilling had no effect on anthocyanins. Although TWC decreased and anthocyanin level increased\nfrom active growth to the beginning of frost hardening, no increase was observed during frost\nhardening. Ni did not cause drought stress in the aboveground shoots, but anthocyanin level\ndecreased in the aboveground shoots along with Ni accumulation in the belowground stems. Na+\nincreased TWC in the belowground stems, but decreased TWC and anthocyanin level in the\naboveground stems.\nIt is proposed that anthocyanins do not have direct role in osmotic regulation, or in the\ndevelopment of freezing tolerance. It is suggested that the increase in anthocyanin level under\ndirect drought stress is mainly due to the photoprotection of chlorophylls by anthocyanins. This is\nsupported by two facts: (1) At increased anthocyanin level in the juvenile leaves, chlorophyll a\nwas stabilized despite continuing drought stress, and (2) after the initial peak in the mature leaves,\nthe accumulation of anthocyanins ceased although the drought became more severe. As\nchlorophyll a decreased in the mature leaves due to senescence, there was less demand for such\nhigh levels of anthocyanins.

ISBN-10:
978-951-42-6204-3
Kieli:
eng.
Sivumäärä:
118 s.
Tekijät:
Tahkokorpi Marjaana
Tuotekoodi 013984
20,00 €