Under Low Temperature Stress, The Changes Of Some Physiological Characteristics Of The Two Tropical Acacia

The intact seedlings of Acacia auriculiformis A. Cunn and A. mangiumWilld were exposed to low temperature under humid conditions whichprevented dehydration. Effects of low temperature stress on physiologyand biochemistry of the two species were tested. And the survival of thetwo species was recorded after chilling treatment. The effect ofpretreatment with abscisic acid(ABA) prior to low temperature, which wasarranged in 4 leyels of both concentration and pretreatment time, wasdetermined by means of electrolyte loss in the leaves of A. mangium under3℃ and 0℃. Relationships between the tested index and the survivalrates of both species were also analyzed. Main results are given asfollows:(1)The potential ability of cold resistance between the two specieswas greatly different. When exposed to the low temperature of both 3℃ and 0℃, the electrolyte loss in the leaves of both plants wassignificantly increased compared to the controls. Leakage ofelectrolytes of A. mngium reached 13. 37% and 21. 23% of the total amountin the leaves, and that of A. auriculiformis reached about l7. 39% and32. 32% reciprocally. When exposed to 6℃, the leaves of A. mangiumwilted, while not for A. auriculaeformis until under 3℃. Under thelower temperature of 3℃, the leaves of the former were severely wiltedand parts of the leaves appeared to be water logging at the same time.(2)Under low temperature stress, the contents of the soluble sugar,the soluble protein and the free proline are increased significantly.There are significant correlation between them and the survival of theseedlings.(3) When exposed to the chilling temperature the net photosyntheticrate and transpiration rate were decreased significantly, while theactivity of S0D increased in the whole.(4) The analysis of the relationship among all the index showed thatthe re1ative co-efficient between the electro1yte 1oss and the survivalof the seedlings and the so1uble protein were more than 0. 9. The re1ativeco-efficient between the survival and the rmA contat, S0D activity andthe net photosynthesis rate were larger than 0. 6. So the above indexshould be applied to appraised the cold resistance of both species. Theco - efficient between the free proline and the surviva1 ofA. aUrjcu1ibos was 0. 8059, but it was 0. 3093 of A. edum(5) The co1d resistance of seed1ings of both species was increasedby pretreatment with abscisic acid. The resu1t showed that thepretreatment of either 10-'M ABA for 24 hOurs or 10fe A8A for 36 hours wasthe optimum treatments to improve p1ant co1d resistance.