Comparison of Cold Hardiness Evaluation of Woody Species by ELLT and TTCLT

Cold hardiness evaluation is important for screening woody species in cold areas. We compared cold hardiness by estimating the 50% lethal temperature (LT 50 ) using electrolyte leakage test (ELLT 50 ) and triphenyltetrazolium chloride test (TTCLT 50 ) for 26 woody species in the Bashang region of China. One-year-old shoots were collected in January and exposed to five subfreezing temperatures in a programmable temperature and humidity chamber. LT 50 was estimated by fitting relative electrolyte leakage and percentage of dead tissue against test temperature. For all tested species, triphenyltetrazolium chloride (TTC) staining of the pith was weak and the cambium TTCLT 50 was lower than the extreme minimum temperature (−37 °C) recorded in the region. The cambium TTCLT 50 and the sd were lower than that for the phloem and xylem. The phloem TTCLT 50 was lower than the xylem TTCLT 50 , and the two sd s were similar. The ELLT 50 showed no significant correlation with any TTCLT 50. For most species, the ELLT 50 was higher than the cambium and phloem TTCLT 50 and was not significant different with the xylem TTCLT 50 . The ELLT 50 showed higher sd than any tissue TTCLT 50. Based on results obtained in this study, when choosing cold hardiness of single stem tissue as an indicator for screening woody species, the xylem should be considered first, followed by the phloem; the cambium and pith were unsuitable. The cold hardiness estimated by ELLT 50 was more suitable as indicator for screening woody species than that of stem tissue in winter estimated by TTCLT 50 .