Analysis of Principal Components and Subordinate Function on Heat Tolerance of Two Seedlings of Rhododendron Subgenus Hymenanthes

Abstract:

In order to explore the indices and evaluation method of heat tolerance of Rhododendron subgenus Hymenanthes, 4-year-old seedlings of R. jinggangshanicum Tam and R. simiarum Hance were planted in artificial climate chamber under different high temperatures (30℃, 38℃, and with 22℃ as control). The contents of malondialdehyde (MDA), hydrogen peroxide (H₂O₂), proline (Pro), soluble protein, ascorbic acid (AsA) and the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX) were determined after treated for 6 days. The heat tolerance of two species was comprehensively evaluated by principal components analysis and fuzzy subordinate function based on the measurement values of tested parameters. The results showed that MDA, H₂O₂, SOD, CAT, POD, APX were the most important physiological and biochemical indexes for heat tolerance of Rhododendron seedlings. A very significant correlation (r=0.987^**) was found between the subordinate function values (U value) of 6 main indices and U value of whole indices. The U value and increased range of U value in R. simiarum were larger than those in R. jinggangshanicum at 30℃ and 38℃, the evaluation results accorded with their behavior in the field. It is suggested that the method can give an objective evaluation on the comprehensive heat tolerance between different species of Rhododendron subgenus Hymenanthes seedlings.