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Comparison of methods for detecting vulnerability of xylem embolism in Robinia pseudoacacia
AN Rui, MENG Feng, YIN Peng-Xian, DU Guang-Yuan
Chin J Plant Ecol    2018, 42 (11): 1113-1119.   DOI: 10.17521/cjpe.2018.0145
Abstract   (1092 HTML135 PDF(pc) (1502KB)(1276)  

Aims The vulnerability of xylem embolism is one of the key physiological factors that are related to plant mortality. Vulnerability curves are typically used for determining the vulnerability of xylem embolism. However, the shapes of vulnerability curves vary with the methods of assessment, especially in plant species with long xylem vessels. This study aims to investigate the feasibility of using different methods for establishment of vulnerability curves.
Methods Robinia pseudoacacia branches, with long xylem vessels, were used as plant materials for comparison of three different methods in establishing vulnerability curves, including bench top dehydration, Cochard Cavitron centrifugation and Sperry centrifugation. In the Sperry centrifugation method, rotors of two different sizes were used to test the ‘open vessel artifact’ hypothesis.
Important findings The vulnerability curve established by the bench top dehydration method displayed an “s” shape, while both the Cochard Cavitron centrifugation and Sperry centrifugation methods produced “r” shape curves. Vulnerability curves derived from the bench top dehydration method and the centrifugation methods were significantly different. Using the Sperry centrifugation method, the R. pseudoacacia branch samples in the 14.4 cm rotor had a higher proportion of open vessels, while the embolic vulnerability curves established on the 27.4 cm and 14.4 cm long stem segments were similar, indicating that the Sperry centrifugation method does not produce “open vessel artifact”.


Fig. 1 The probability that the xylem conduit is within the length x interval (Px) and stem length (x) derived from the xylem conduit length distribution of Robinia pseudoacacia (mean ± SD).
Extracts from the Article
空气注入法测定出刺槐的导管长度为(20.020 ± 1.835) cm, 根据Cohen理论, 长14.4 cm的茎段所含开口导管的概率为(0.032 ± 0.002)%, 而长27.4 cm的茎段所含开口导管的概率为(0.019 ± 0.002)% (图1)。尽管27.4 cm和14.4 cm的刺槐茎段所含有的开口导管数上有显著性的差异(p < 0.05), 但采用Sperry离心机法在两种长度茎段上建立的VC无明显差异(图2), 它们的P50差异不显著(表1)。
刺槐是一种长导管物种, 本研究得到刺槐的平均导管长度为20.02 cm, 这与最近的一些文献报道的刺槐的平均导管长度为20.55 cm (Wang et al., 2014; 李荣等, 2016)的结果一致, 并且通过近几年报道的各物种的导管长度的数据来看, 刺槐的导管长度比大多数物种长(Jacobsen et al., 2014; 李荣等, 2016)。根据Cohen理论, 两种长度枝条的开口导管概率数分别为0.019%和0.032%, 如果Sperry离心机法在测定刺槐枝条时存在“开口导管假象” (Cochard et al., 2010; Choat et al., 2010), 那么两种不同长度枝条的VC应该有显著差异, 然而试验结果不支持该观点(图1)。近年来, 有研究在测定长导管植物VC时未发现“开口导管假象”(Jacobsen and Pratt, 2012; Sperry, et al., 2012)。例如, Sperry等(2012)用离心机法建立长导管植物Quercus gambelii和其他物种短茎段和长茎段的栓塞脆弱性曲线并没有差别。同时Jacobsen和Pratt (2012)用相同的方法建立的葡萄(Vitis vinifera)的VC, 发现其P50值也无明显差异。相比较而言,Cochard Cavitron离心机法可能更容易出现“开口导管假象” (Cochard et al., 2005)。
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