Department of Biology, University of Oulu, P.O. Box 3000, FIN-90014, Oulu, Finland.
Protoplasma. 2010 May;241(1-4):19-27. doi: 10.1007/s00709-009-0096-x. Epub 2010 Feb 19.
The difference between drought tolerance of juvenile and mature leaves of the winter-deciduous dwarf shrub bilberry (Vaccinium myrtillus L.) from a northern boreal environment was investigated. It was hypothesised that mature leaves are more drought sensitive than juvenile leaves. Bilberry plants were allowed to dry out by excluding irrigation when leaves were at juvenile and mature stages. Tissue water content decreased at both phenological stages, but the response was more pronounced in the mature leaves. Anthocyanin concentrations increased as the tissue water content decreased, and again this occurred to a greater extent in the mature leaves. Chlorophyll concentrations decreased only marginally at the juvenile stage, while the decrease was significant in the mature leaves. Chlorophyll degradation was enhanced by drought stress. Soluble proteins decreased and protein oxidation increased in the mature leaves, and degradation of oxidised proteins increased in the drought-stressed plants. The results suggest that leaves of bilberry are more sensitive to drought stress at the mature stage, and that drought stress accelerates senescence at the mature stage. The significance of the results is that dry periods during the juvenility of leaves are not as detrimental as they may be later in summer. In addition, the strategy of a winter-deciduous plant is obviously to protect its perennial parts from severe drought by accelerated leaf senescence at the mature stage. Therefore, the deciduous life form may provide an excellent adaptation against drought also in northern ecosystems. The role of anthocyanins in photoprotection under drought stress is also discussed.
研究了北方北方环境中冬季落叶矮灌木越桔（ Vaccinium myrtillus L. ）幼叶和成熟叶的耐旱性差异。假设成熟叶比幼叶对干旱更敏感。当叶片处于幼叶和成熟阶段时，通过排除灌溉使越桔植物变干。在两个物候阶段，组织含水量都下降，但在成熟叶片中反应更为明显。随着组织含水量的降低，花青苷浓度增加，在成熟叶片中更为明显。在幼叶阶段，叶绿素浓度仅略有下降，而在成熟叶片中则显著下降。干旱胁迫会增强叶绿素的降解。在成熟叶片中，可溶性蛋白减少，蛋白质氧化增加，氧化蛋白的降解在干旱胁迫下的植物中增加。结果表明，越桔叶片在成熟阶段对干旱胁迫更为敏感，干旱胁迫会加速成熟叶片的衰老。结果的意义在于，在叶片幼年期的干旱期可能不会像夏季后期那样有害。此外，冬季落叶植物的策略显然是通过在成熟阶段加速叶片衰老来保护其多年生部分免受严重干旱。因此，落叶生活型在北方生态系统中也可能是一种很好的抗旱适应。还讨论了花青苷在干旱胁迫下的光保护作用。
