Abstract:

Abstract： This study was conducted to assess the impact of leaf age on nutrition，biomass of leaf layer，content of chlorophyll and variety of leaf shape in tetraploid Robinia pseudoacacia. At an interval of 10 d from budbreak the leaf shape, and chlorophyll and nutrients in leaves were measured. The results showed that the leaf nutrition value was at the best level during the first 45 days，and for the same aged leaves，higher during the growing period than the decaying stage. In addition，the biomass of 35～45 d leaf layer reached the highest level. The results also indicated that young leaves contained low content of chlorophyll，which increased gradually to higher levels during the leaf developing stages until it climbed up to the climax. It then decreased with the leaf senility. As for the leaves of the same age，their chlorophyll a，chlorophyll b and the total chlorophyll contents differed in various growth stages. The leaf shape changed rapidly during the first 20 d and then kept a slow pace in developing. The statistics further revealed positive correlations between leaf age and the contents such as ether extract，ash，calcium，as well as leaf length and leaf area (length×width)； while the contents of crude protein and phosphor of the same aged leaves demonstrated negative correlations with different growing stages.

Key words: Key words： tetraploid Robinia pseudoacacia, leaf age, nutrition of leaves, biomass of leaf layer, chlorophyll, leaf shape