Department of Botany, University of Innsbruck, A-6020 Innsbruck, Austria.
Plant Physiol. 2014 Feb;164(2):992-8. doi: 10.1104/pp.113.228403. Epub 2013 Dec 16.
Freeze-thaw events can affect plant hydraulics by inducing embolism. This study analyzed the effect of temperature during the freezing process on hydraulic conductivity and ultrasonic emissions (UE). Stems of 10 angiosperms were dehydrated to a water potential at 12% percentage loss of hydraulic conductivity (PLC) and exposed to freeze-thaw cycles. The minimal temperature of the frost cycle correlated positively with induced PLC, whereby species with wider conduits (hydraulic diameter) showed higher freeze-thaw-induced PLC. Ultrasonic activity started with the onset of freezing and increased with decreasing subzero temperatures, whereas no UE were recorded during thawing. The temperature at which 50% of UE were reached varied between -9.1°C and -31.0°C across species. These findings indicate that temperatures during freezing are of relevance for bubble formation and air seeding. We suggest that species-specific cavitation thresholds are reached during freezing due to the temperature-dependent decrease of water potential in the ice, while bubble expansion and the resulting PLC occur during thawing. UE analysis can be used to monitor the cavitation process and estimate freeze-thaw-induced PLC.
冻融事件会通过诱导栓塞来影响植物的水力学特性。本研究分析了冻结过程中温度对导水率和超声发射（UE）的影响。将 10 种被子植物的茎脱水至水势为 12%导水率损失百分比（PLC），然后暴露于冻融循环中。霜循环的最低温度与诱导的 PLC 呈正相关，其中导管较宽（水力直径）的物种表现出更高的冻融诱导 PLC。超声活动随着冻结的开始而开始，并随着亚零温度的降低而增加，而在解冻过程中没有记录到 UE。在不同物种中，达到 50% UE 的温度在-9.1°C 和-31.0°C 之间变化。这些发现表明，冻结过程中的温度与气泡形成和空气播种有关。我们认为，由于冰中水分势随温度的下降而下降，导致在冻结过程中达到了特定物种的空化阈值，而气泡膨胀和由此产生的 PLC 则发生在解冻过程中。UE 分析可用于监测空化过程并估计冻融诱导的 PLC。
