Comparative Study Of Frost Hardiness Of Ligustrun Lucidum And Several Other Ornamental Trees

Sophora japonica‘Golden Stem’, Sophora japonica var. 1oligpophylla, Malus micromalus Mak., Malus spetabilis Royalty, Chimonanthus praecox (L.) Link and Ligustrun lucidum Ait. are the common ornamental trees of landscape. Especially Ligustrun lucidum Ait. is an uncommon evergreen broad-leaved tree growing in the northern landscapes, which has high practical value. However, it originats from southern China and has lower cold resistance. This experiment studied on the frost hardiness (FH) of ornamental trees in order to provide theoretical basis for FH during the dehardering. The electrical impedance spectroscopy (EIS), FH and some physiological indexes, such as moisture content, soluble sugar and starch, as well as proline content of stem were analyzed. The FH was determined by means of the EIS and electrolyte leakage (EL) methods. The changes of the parameters of EIS and the physiological indexes were verified, and their correlations were found. The main results are as follows:1. As dehardening process, the FH of six ornamental trees gradually decreased. The FH of the six ornamental trees was the highest in the early of April during dehardening, and their FH order was Malus spetabilis Royalty > Malus micromalus Mak. > Sophora japonica var. 1oligpophylla > Sophora japonica‘Golden Stem’> Chimonanthus praecox (L.) Link > Ligustrun lucidum Ait. And the FH of Ligustrun lucidum Ait. was 18.1℃lower than that of Malus spetabilis Royalty. The FH of the six ornamental trees was the lowest in the early of May during dehardening, and the FH order was Ligustrun lucidum Ait. > Malus micromalus Mak. > Malus spetabilis Royalty > Chimonanthus praecox (L.) Link > Sophora japonica var. 1oligpophylla > Sophora japonica‘Golden Stem’, and the FH of Sophora japonica‘Golden Stem’was 3.5℃lower than that of Ligustrun lucidum Ait..2. With the enhancement of the FH, some changes occurred for the EIS parameters and electrical impedance spectra of six ornamental trees during dehardening.3. During dehardening, there was a high correlation between the soluble sugar and the specific extracellular resistance re of Sophora japonica‘Golden Stem’, as well as re of Sophora japonica var. 1oligpophylla (R~2=0.91; 0.95). There was also a higher correlation between the soluble sugar and the distribution coefficient of relaxation timeψof Sophora japonica var. 1oligpophylla; the starch content and the re, the specific intracellular resistance ri of Ligustrun lucidum Ait.; the soluble sugar and ri of Chimonanthus praecox (L.) Link; the soluble sugar and the relaxation timeτ, as well as theψof Ligustrun lucidum Ait.4. During dehardening, the Protein contents and Proline contents of ornamental trees changed. The same or opposite trends between the Protein contents, Proline contents and some of EIS parameters were found with a certain degree of correlation between them.5. During dehardening, the FH correlated with the water content, the soluble sugar and starch contents, Protein contents, and Proline contents, so these physiological indicators could be used to estimate the frost hardiness.6. During dehardening, the FH measured by EL and the EIS parameters re andτwithout frozen treatment (R~2=0.94-0.96), thus these two EIS parameters could be used to estimate the FH of ornamental trees.