Abstract
Morphological development of forced tree peony (Paeonia suffruticosa) was observed in 17 Chinese and 3 Japanese cultivars (cvs) and the effects of pre-chilling on the growth and development in the Chinese and Japanese cv groups were compared. The development from bud swelling to flowering was divided into 8 stages. The leaves, stem and flower buds mainly grew during stages IV-VII, and stage VI was the longest showing the most vigorous growth. Stages III, IV and V were very complicated in morphology and varied with the cv, but could be identified easily by the leaf development. The pre-chilling promoted the growth and advanced the flowering, but the stage sensitive to the chilling in the Chinese cvs differed from that in Japanese cvs, which indicated the existence of different growth mechanisms. The pre-chilling was effective at the early stages in the Chinese cvs, but at the later stages in the Japanese cvs. The Chinese cvs grew more rapidly and responded to low temperature at an earlier stage, but their cut flower quality was inferior to the Japanese cvs. These results corresponded to a smaller requirement of cumulative temperature for flowering in the Chinese cvs. The pre-chilling decreased the stem length and foliage extension, but promoted the flower size and advanced the flowering date. Non-flowering cvs had normal leaves developed a normal stem and responded to pre-chilling as well as did the flowering cv. These results suggested that the vegetative growth is somewhat independent of the generative growth.
