Abstract:

For testing the practicability of using portable non_destructive meter of SPAD-502 and Agriexpert PPW_3000 for measuring the chlorophyll and leaf nitrogen changes during leaf autumn senescence, two local species of Syringa oblata, Maackia amurensis and one introduced species from north China, Amorpha fruticosa were measured from late summer (September) to late autumn (October) of 2003 by these SPAD-502, PPW-3000 and standard chemical method. The results showed that: 1) Readings from the two instruments could represent chlorophyll a,b and a+b and nitrogen content per unit leaf area, rather than per unit leaf fresh mass; 2) Although a general linear tendency between readings of PPW-3000 and SPAD-502 and real values of chlorophylls and nitrogen through 3 species was observed (R² =0.51～0.65),readings from these 2 instruments alone could not effective identify the real difference among these 3 species. Therefore, a calibration line for each species between real values and the readings should be determined in the interspecies comparison; 3)When description of chlorophyll and nitrogen difference in different phases of leaf autumn senescence, two equipments could effectively descript the chlorophyll and nitrogen changes of two local species of S. oblata, M. amurensis (R²>0.82). However, they could not make effective description in the case of introduced species of A. fruticosa (R²<0.66), and sometimes the correlation was not significant. The reason for this might be attributed to the fact that, comparing with local species, chlorophyll of introduced species didn’t degrade simultaneously with leaf autumn senescence and dewatering. Thus, these two instruments are more suitable for measuring local species with simultaneous changes in leaf senescence and chlorophyll degradation; 4)Comparison on the practicability between PPW-3000 and SPAD-502 showed no obvious difference on the description of chlorophylls and nitrogen changes in the case of local species of S. oblata, M. amurensis. However, PPW-3000 showed better description on nitrogen changes of introduced species of A. fruticosa than SPAD-502.

Key words: Syringa oblata, Maackia amurensis, Amorpha fruticosa, SPAD-502, PPW-3000, chlorophyll, nitrogen