Studies On Endogenous Hormones During Phase Change In Seedling Plant Of Malus Hupenhensis

Phase change, the transition from juvenility to maturity is an intriguing phenomenon in wood perennials. During the whole life cycle, there is a juvenile zone at the base of seedling which has inability to flowering. It has been proved that the phase change is associated with progressive changes in physiological and morphological characteristics, and the plant height is the most important factor that governs phase change of seedlings. In order to avoid zygotic diversity effect within seedlings and to provide more evidences for the mechanism of phase change, apomixis seedlings of crabapple (Malus hupenhensis) were selected as trial material ,and the scions from various height of a seedling were grafting to the 4-year old stocks which had been pruned back at the height of 30cm previously to remove the environment affect coming from the various regional factors of seedling's height. The relationship between plant height and endogenous hormone's(GA,,IAA,ABA and ZT) content and their ratio were studied by HPLC analysis. The main results are summarized below:1. The content of endogenous GA3 decreased with plant height both in the seedling and in the grafting, and made an emergency landing in the zone of 150-200cm,that was just the zone of the lowest zone of emerging flowers. The content of IAA and ZT decreased in the juvenile zone and appeared a peak in the zone of 150-200cm.In the adult zone, the content of IAA raised again, but the content of ZT hardly changed. The content of ABA in the adult zone were higher than the ones in the juvenile zone ,and appeared a peak in the middle zone of 150-200cm.2. The ratios of ABA/GA3,ZT/GA3,IAA/GA3, IAA/ZT were rarely changed in the juvenile zone, and appeared a peak value when the juvenile shift to the transition zone in 150-200cm,and showed a tendency to increasing again in adult zone.3. The seasonal changes in the content of endogenous GA3,IAA and ZT showed the same trend within all the three zone:in May and July ,when the shoots of seedling were growing fast, the contents were more than in June and August,when the growth of seedling shoots were slow down.The AliA's content increased in whole the growth season and reached it's maximum in Agust.4. Grafting the scions from various height of a seedling to the 2-year old stocks which had been pruned back at the height of 30cm previously could clear up the affect from the various regional factors of seedling's height.The results of analysis of the grafted materials is similar to that of seedlings'.Which showed the plant height was an important factor of phase change.At last ,the mechanism of phase change was also discussed.