Study On The Physiological And Biochemical Changes In Avrolles (Malus Domestica) After Natural Dormancy Releasing

This experiment was carried out in'xiaojinkou'apple orchard of Tai'an and Horticultural experiment station of Shandong Agricultural University from 2006 to 2009. Avrolles (Malus domestica), which germinates 20d later than some other apple varieties (such as Golden Delicious, Fuji, Judeline(Malus domestica), etc.) and can avoid late frost damage, was used to research the ecological features (light and temperature) and physiological and biochemical changes (endogenous hormones, respiratory metabolism and phenolic substances, etc.) from natural dormancy releasing to germination. Taking Judeline for control, the main results were as follows:1. Methods of water cultivation in the artificial lighting incubator and water state determination were used to test the dormancy state of Avrolles and Judeline. The date of bud dormancy releasing of Avrolles was at the end of January, while Judeline at the end of December, one-month difference between the two varieties. Using 0～7.2℃model to estimate the chilling requirement of natural dormancy releasing, Avrolles'chilling requirement (1200～1500 h) was, about two times higher than that of Judelin (600～850 h). The phenological observation showed that Avrolles geminated at mid-and-late April, while Judeline at mid-and-late March. 5°C was usually treated as the initial temperature to calculate the efficiently accumulative temperature of germination. The sum of efficiently accumulative temperature (∑T) was 320～380°C and 100～150℃for Avrolles and Judeline, respectively. When growth degree hours (GDH℃) was used to calculate the heat requirement of germination, Avrolles was 7800～9300 GDH℃at the green opened in buds, which was 1.7 times higher than that in Judeline. These showed that Avorlles required not only higher chilling requirement, but also higher heat requirement. The heat requirement of germination in Avrolles reduced when the chilling requirement was added, but the relation was not reciprocity, adding more 5d and 10d chilling requirement, the heat requirement only replaced 80% and 60%, respectively. The length of sunshine had little effect on germination.2. The content of endogenous hormone in buds showed that growth-promoting hormones, such as GA3, IAA and ZR, increased while growth-inhibiting hormones, such as ABA, declined, with the natural dormancy released. During the procedure of germination, GA3 concentration of Avrolles was significantly higher than that of Judeline at the same period. In addition, GA3 concentration and the ratio of GA3/ABA were 1.55 and 2.08 times higher than that of Judeline before germination, respectively. The time for ZR concentration increasing in Avrolles was 26d longer than in Judeline. The value of ZR and ZR/ABA were 2.12 and 1.55 times higher than that of Judeline, respectively, while the ratio of GA3 + IAA + ZR)/ABA was 1.59 times as large as that of Judeline. That indicated that a relatively higher concentration of growth-promoting hormones (GA3, ZR etc. ) was required in the germination process of Avrolles, which led to the high ratio of GA3/ABA, ZR/ABA and (GA3 + IAA + ZR)/ABA, compared with Judeline3. The total and EMP respiration intensity of Avrolles were less than that of Judeline, only 84.6% and 84.7% at the highest point, respectively. PPP accumulation in Avrolles was 21 days longer than that in Judeline. Furthermore, the running activity was higher and the increased amplitude was 2.02 times than that in Judeline. With the bud dormancy releasing and germination proceeding, the content of soluble sugar which as the substrate of respiration, increased, while starch content declined for transforming into soluble sugars. Soluble sugar content of Avrolles was significantly lower than that of Judeline at the same period.4. The respiration rate of buds declined with adding inhibitor of electron transfer (KCN and SHAM), which implied the existence of both cytochorome pathway and cyanide-resistant pathway in the buds. In contribution rate to total respiration (ρ'Vcyt/Vt), the cytochorome pathway was always higher than cyanide-resistant pathway, which indicated that cytochorome pathway was the main electron transfer pathway. During the whole germination process, the respiration rate of cyanide-resistant pathway,ρValt/Vt and the coefficient of running(ρ)in buds of Avrolles were always higher than that of Judeline, which indicated that the germination of Avrolles required high activity of electron transfer in cyanide-resistant pathway to supply energy to resist the low external temperature.5. Compared with Judeline, Avrolles had the low O2-. production and H2O2 level, and the activity of antioxidase and content of substance resisting oxidation in the process of germination, which indicated that the metabolism rate of active oxygen in the buds of Avrolles was lower than that of Judeline. O2-. mainly comes from the electron leak of mitochondrion respiration. POD played an important role in eliminating H2O2 at the early stage of germination, while CAT at the late stage of germination. Content of GSH and AsA increased in the process of germination which indicated that the AsA-GSH Cycle had been started in the process of the elimination of active oxygen. 6. With the dormancy deepening, content of total phenolics and activity of PAL rised. As the dormancy released, content of total phenolics and activity of PAL declined while activity of PPO increased, which indicated that total phenolics was a germination inhibitor. Compared with Judeine, Avrolles had the high the content of total phenolics, the activity of PAL and PPO, of which the total phinolics content was 25% higher. That indicated that the late-germination of Avrolles was related to metabolism of total phenolics. By HPLC, the content of six monophenols, i.e. gallic acid, epicatechin, meletin, phloretin, ferulic acid and caffetannic acid, were measured. The content of meletin followed by epicatechin was the highest, while the content of gallic acid was the lowest. The content of epicatechin in the buds of Avrolles was 1.31 times higher than that of Judeline, the content of phloretin was 76.8% lower than that of Judeline. The content of ferulic acid increased as the dormancy strengthened while it declined in the process of germination, which indicated that ferulic acid was an inhibitor of germination.