Reconciling discrepancies in measurements of vulnerability to xylem embolism with the pneumatic method
Reconciling discrepancies in measurements of vulnerability to xylem embolism with the pneumatic method
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DOI：
10.1111/nph.18531
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发表时间：
2023-01-01
期刊：
影响因子：
9.4
通讯作者：
Saleska, Scott R.
中科院分区：
文献类型：
--
作者：
Brum, Mauro;Pereira, Luciano;Saleska, Scott R.
Chen 等人（2021）报告了气动方法与其他测量植物木质部组织栓塞脆弱性的方法之间的差异，导致他们警告不要使用气动方法。我们表明，这种差异源于错误的实施：未能测量足够负水势的空气排放量，他们低估了最大空气排放量（ADmax），从而低估了栓塞阻力。栓塞脆弱性方法确定茎必须脱水到什么程度（水势，P50）才能导致木质部电导率损失 50%。气动方法需要测量的水势大约是 P50 脱水量的两倍。然而陈等人。通常会在比其他方法显示的 P50 更低的幅度上停止，这使得他们的气动实施在数学上不可能测量真实的 P50。我们的模拟证实，过早停止会导致派生的 P50 产生较大误差，从而解释了报告的差异。此外，文献研究表明气动方法和其他方法之间存在一致的一致性。因此，Chen 等人的气动结果是无效的，不应被视为破坏气动测量的信心。我们推荐最佳实践，包括用于自动测量的“Pneumatron”，以防止 Chen 等人的错误。并对栓塞脆弱性进行快速、可复制且准确的气动测量。
Chen et al.(2021) reported discrepancies between pneumatic and other methods for measuring embolism vulnerability in plant xylem tissue, leading them to caution against using the pneumatic method. We show that this discrepancy arises from faulty implementation: failing to measure air discharge to sufficiently negative water potentials, they under-estimated maximum air discharge (ADmax), and hence embolism resistance. Embolism vulnerability methods identify how dehydrated a stem must become (in water potential, P50) to cause a 50% loss in xylem conductivity. Pneumatic methods require measurements to water potentials roughly twice as dehydrated as P50. Yet Chen et al. often stopped at magnitudes even less than what other methods showed P50 to be, making it mathematically impossible for their pneumatic implementation to measure true P50. Our simulations confirmed that premature stopping causes large errors in derived P50, accounting for reported discrepancies. Further, literature studies show consistent agreement between pneumatic and other methods. Thus, Chen et al.’s pneumatic results are invalid, and should not be taken to undermine confidence in pneumatic measurements. We recommend best practices, including the ‘Pneumatron’for automated measurements, that prevent the errors of Chen et al. and make pneumatic measurements of embolism vulnerability that are fast, replicable, and accurate.