莲雾苗低温危害等级划分标准初探

为了解低温对莲雾苗的影响，采用盆栽方法在人工气候箱内对1a生莲雾嫁接苗(黑珍珠)进行低温处理，日最低温度(Tmin)分别设定为2.0、1.0、0.0、?1.0、?2.0℃，气温日较差分别设为15℃和6℃，按照固定程序设置日内温度变化过程，每个处理持续1～3d。处理结束当日分别对莲雾苗形态和生理生化指标进行观测,常温下放置10d后再观测其恢复状况，依此对造成莲雾苗叶片和枝条受害的界限低温进行分析，初步构建莲雾苗冷害指标等级。利用地理移置试验观察莲雾苗形态的变化，以对人工控制试验建立的指标进行检验和订正，得到莲雾苗低温危害等级指标。结果表明，地理移置试验结果与人工控制试验结果相一致。莲雾苗的冷害指标等级分别为：（1）Tmin≤?2℃致死，（2）?2℃＜Tmin≤?1℃严重受冻，（3）?1℃＜Tmin≤2℃中度受冻，（4）2℃＜Tmin≤5℃轻度受冻，若Tmin在2~5℃间持续3d以上，且持续时间越长，温度越低，莲雾苗的部分叶片会因低温而干枯脱落，并影响后期生长；（5）Tmin＞5℃正常生长。

Effects of Low Temperature Stress on Syzygiums amarangense Seedlings and Its Cold(Frozen)Injury Grades Index

In order to establish the low temperature injury grades on Syzygiums amarangense, one year old Syzygiums amarangense graft seedlings (var. Black Pearl) were treated in the climate chamber for 1day, 2 days and 3 days respectively, where the daily minimum temperature (Tmin) were set at 2℃, 1℃, 0℃, ?1℃ and ?2℃, the diurnal temperature differences were set 15℃ (radiation temperature decrease) and 6℃ (temperature decrease with highly humidity). There were 10 treatments, and each treatment included 3 replicates. 3 plants was as CK in nature light in fields (photo flux density was 300～500μmol·m?2·s?1） under normal atmospheric temperature（daily average temperature was 15～20℃). Morphological changes of S. amarangense graft seedling were observed and recorded both immediately and 10 days after treatment. Those physiological and chemical index related stress were detected, such as soluble sugars, proline, soluble proteins, and MDA concentrations, SOD activity, relative electrical conduction in its leaves. The critical temperatures that injured the leaves and branches of S. amarangense graft seedling were preliminary analyzed. The cold injury indexes of S. amarangense seedling were established depending on the morphological changing, the physiological index variation with the Tmin changing and its durations. In order to verify and test the injury index that established with controlling conditions. Morphological changes of S. amarangense graft seedling were observed in different elevations and latitudes. The results showed that the injury critical temperature index obtained from controlled conditions were consistent to geographical displacement test. The low temperature injury index were divided into 5 grades, that were, (1)death, Tmin≤?2℃; (2)serious injury, ?2℃＜Tmin≤?1℃; (3)moderate injury, ?1℃＜Tmin≤2℃; (4)light injury, 2℃＜Tmin≤5℃, lasting for more 3 days the leaves of S. amarangense seedlings maybe fall off, and the following growth should be affected. The grades of death; (5)normal, Tmin＞5℃.