Institute of Botany, Unit Functional Plant Biology, University of Innsbruck, Sternwartestrasse 15, A-6020 Innsbruck, Austria.
Tree Physiol. 2011 Nov;31(11):1217-27. doi: 10.1093/treephys/tpr103. Epub 2011 Oct 18.
Winter frost resistance (WFR), midwinter frost hardening and frost dehardening potential of Pinus cembra L. were determined in situ by means of a novel low-temperature freezing system at the alpine timberline ecotone (1950 m a.s.l., Mt Patscherkofel, Innsbruck, Austria). In situ liquid nitrogen (LN₂)-quenching experiments should check whether maximum WFR of P. cembra belonging to the frost hardiest conifer group, being classified in US Department of Agriculture climatic zone 1, suffices to survive dipping into LN₂ (-196 °C). Viability was assessed in a field re-growth test. Maximum in situ WFR (LT₅₀) of leaves was <- 75 °C and that of buds was less (-70.3 °C), matching the lowest water contents. In midwinter, in situ freezing exotherms of leaves, buds and the xylem were often not detectable. Ice formed in the xylem at a mean of -2.8 °C and in leaves at -3.3 °C. In situ WFR of P. cembra was higher than that obtained on detached twigs, as reported earlier. In situ LN₂-quenching experiments were lethal in all cases even when twigs of P. cembra were exposed to an in situ frost hardening treatment (12 days at -20 °C followed by 3 days at -50 °C) to induce maximum WFR. Temperature treatments applied in the field significantly affected the actual WFR. In January a frost hardening treatment (21 days at -20 °C) led to a significant increase of WFR (buds: -62 °C to <- 70 °C; leaves: -59.6 °C to -65.2 °C), showing that P. cembra was not at its specific maximum WFR. In contrast, simulated warm spells in late winter led to premature frost dehardening (buds: -32.6 °C to -10.2 °C; leaves: -32.7 to -16.4 °C) followed by significantly earlier bud swelling and burst in late winter. Strikingly, both temperature treatments, either increased air temperature (+10.1 °C) or increased soil temperature (+6.5 °C), were similarly effective. This high readiness to frost harden and deharden in winter in the field must be considered to be of great significance for future winter survival of P. cembra. Determination of WFR in field re-growth tests appears to be a valuable tool for critically judging estimates of WFR obtained on detached twigs in an ecological context.
在奥地利因斯布鲁克的帕彻尔科普费尔山（海拔 1950 米）的高山林线生态交错带，利用一种新型的低温冷冻系统，对欧洲赤松的冬季抗冻性（WFR）、隆冬抗冻能力和抗冻恢复能力进行了原位测定。原位液氮（LN₂）淬火实验应检查属于最抗冻针叶树群的欧洲赤松的最大 WFR（被美国农业部气候带 1 分类）是否足以承受浸入 LN₂（-196°C）。在野外再生长试验中评估了其生存能力。叶片的最大原位 WFR（LT₅₀）为-75°C，芽的最大原位 WFR 为-70.3°C，这与最低含水量相匹配。隆冬时，叶片、芽和木质部的原位冻结放热通常无法检测到。冰在木质部中形成的平均温度为-2.8°C，在叶片中形成的平均温度为-3.3°C。与之前报道的相比，欧洲赤松的原位 WFR 高于从离体小枝获得的 WFR。即使将欧洲赤松的小枝暴露于原位抗冻处理（-20°C 下 12 天，然后在-50°C 下 3 天）以诱导最大 WFR，原位 LN₂淬火实验也会导致死亡。在现场进行的温度处理对实际的 WFR 有显著影响。1 月进行的抗冻处理（-20°C 下 21 天）导致 WFR 显著增加（芽：-62°C 至<-70°C；叶片：-59.6°C 至-65.2°C），表明欧洲赤松未达到其特定的最大 WFR。相比之下，早春的模拟暖期导致过早的抗冻恢复（芽：-32.6°C 至-10.2°C；叶片：-32.7°C 至-16.4°C），随后早春芽的肿胀和破裂明显提前。值得注意的是，无论是升高空气温度（+10.1°C）还是升高土壤温度（+6.5°C），这两种温度处理都同样有效。这种在冬季现场进行的高度抗冻和抗冻恢复的能力必须被认为对未来欧洲赤松在冬季的生存具有重要意义。在野外再生长试验中测定 WFR 似乎是批判性判断在生态背景下从离体小枝获得的 WFR 估计值的一种有价值的工具。
