Kong Ricky S, Henry Hugh A L
Department of Biology, University of Western Ontario, 1151 Richmond St. N., London, ON, Canada, N6A 5B7
Department of Biology, University of Western Ontario, 1151 Richmond St. N., London, ON, Canada, N6A 5B7.
Am J Bot. 2016 Nov;103(11):1890-1896. doi: 10.3732/ajb.1600176. Epub 2016 Nov 1.
Both freezing and drought cause cellular dehydration, and they elicit similar increases in protective compounds, which suggests that these stresses could potentially interact. We examined whether the physiological changes that occur in response to freezing in the fall and spring could affect subsequent survival and growth after summer drought.
We froze Poa pratensis tillers in the late fall, early spring, or late spring at 0, -5, or -10°C for 3 d and then subjected them to no drought (-0.025 MPa), moderate drought (-0.140 MPa), or severe drought (-0.250 MPa) for 3 wk in the summer. We quantified survival and total biomass after a 3-wk recovery period, and we determined leaf soluble sugar concentrations before and then 0, 30, and 55 d after freezing.
For survival and biomass, there were significant interactions between freezing and drought. Spring frozen tillers had the highest biomass and survival following severe drought, whereas fall freezing did not significantly increase the biomass of tillers following the severe drought. Increased drought tolerance after spring freezing did not appear to be associated with increased soluble sugar content, given that the freezing effects on leaf glucose, fructose, and sucrose content were absent 55 d post freezing.
Our results demonstrate that multiple stresses that occur over different seasons can interact; this interaction is highly relevant to herbaceous species in northern temperate regions that are experiencing more intense and frequent stress as a result of changes in snow cover and extreme climatic events.
冷冻和干旱都会导致细胞脱水，并且它们会引发保护性化合物的类似增加，这表明这些胁迫可能会相互作用。我们研究了秋季和春季因冷冻而发生的生理变化是否会影响夏季干旱后的后续存活和生长。
我们在深秋、早春或晚春将草地早熟禾的分蘖在0、-5或-10°C下冷冻3天，然后在夏季使其遭受无干旱（-0.025兆帕）、中度干旱（-0.140兆帕）或重度干旱（-0.250兆帕）处理3周。我们在3周的恢复期后对存活率和总生物量进行了量化，并在冷冻前以及冷冻后0、30和55天测定了叶片可溶性糖浓度。
对于存活率和生物量，冷冻和干旱之间存在显著的相互作用。春季冷冻的分蘖在重度干旱后具有最高的生物量和存活率，而秋季冷冻在重度干旱后并没有显著增加分蘖的生物量。春季冷冻后耐旱性的提高似乎与可溶性糖含量的增加无关，因为在冷冻后55天，冷冻对叶片葡萄糖、果糖和蔗糖含量没有影响。
我们的结果表明，不同季节发生的多种胁迫可能会相互作用；这种相互作用与北温带地区的草本物种高度相关，由于积雪覆盖变化和极端气候事件导致这些物种正经历更强烈和频繁的胁迫作用。
