Studies On Cyanide-resistant Respiration Of Nectarine Buds During Endodormancy Induction

The reseach had been carried out in horticultural experimental station and laboratory of protected pomology of Shandong Agricutural University from 2006 to 2007 with nectarine trees. In order to study effects of different treatments on operation regulations of two main electron transport pathways in nectarine buds during endodormancy induction, total respiration rate (Vt), the development and operation of the alternative pathway and partitioning of electrons between the cytochrome and alternative pathways of nectarine buds under supplemental light and shade treatments and natural condition were investigated. In the same time, some physiological changes during endo- dormancy induction were studied. Mechanism of cyanide-resistant respiratory participating in endodormancy induction was discussed. The main results were as follows:1.Endodormancy of buds were induced by shortenning photoperiod and low temperature and shoots stopped growing was the main character.Under natural condition, buds entered the state of endodormancy induction on September 16th. Supplemental light treatment postponed the beginning of endodormancy induction (September 13th) for one week or so. Shade treatment advanced the beginning of endodormancy induction by one week.2.Changes of Vt of flower and leaf buds showed single and double hump- shaped curves, respectively, indicating that mechanisms of respiratory metabo- lism in flower and leaf buds were different. Changes of Valt andρValt of buds under different conditions showed that high jumps in the capacity and activity of the alternative pathway were prominent character. Natural low temperature in autumn increased the flux of electrons to the alternative pathway when Vt ascending, while short photoperiod declined the flux of electrons to the alternative pathway when Vt ascending. These results showed that induction mechanisms of natural low temperature in autumn and short photoperiod were different. It was interesting to note thatρ′Vcyt /Vt was always further higher thanρValt/Vt. Therefore, during endodormancy induction, the cytochrome pathway was the main pathway for mitochondrial electron transport in buds.3. With development of the process of endodormancy induction, physiolo- gical metabolism, such as water concentration and status, membrane permea- bility, soluble protein, carbohydrate and proline concentration changed significantly. Total water concentration of buds showed a rising trend the end of September and beginning of October and then declined until stabilizing at lower level, indicating that buds were going into the state of endodormancy. Relative electral conductivity and malondialdehyde concentration of buds both showed falling trends, especially in flower buds. Soluble protein and proline concentration of buds both showed rising trends with the process of endo- dormancy induction and then remained at higher level at the end of endo- dormancy induction. Dehydrins which were synthesized in late autumne were one of the possible reasons for above changes. Soluble sugar and starch con- centration of nectarine buds gradually accumulated in endodormancy inducti- on, but it was not essential for this conversion because changes of them didn't showed the characteristic of one rising after another declining.The correlation between the process of endodormancy induction and physiological indices showed that concentrations of bund water, soluble protein, soluble sugar, starch and proline positively correlated with the process of endodormancy induction, and correlation coefficients decreased in the order of bund water, starch, proline, soluble protein and soluble sugar concentration. Concentrations of free water and malondialdehyde, and relative electral conductivity negatively correlated with the process of endodormancy induction, and correlation coefficients decreased in the order of free water concentration, malondialdehyde concentration and relative electrical conduc- tivity. Total water concentration of buds had little correlations with the process of endodormancy induction. The correlation coefficients of relative electrical conductivity, free water, malondialdehyde, starch and proline concentration and the process of endodormancy induction were significant.4. Valt andρValt of flower buds positively correlated with concentrations of soluble sugar, starch and proline, and negatively correlated with relative electrical conductivity and malondialdehyde concentration. However, these were opposite in leaf buds.ρ′Vcyt of buds positively correlated with concentration of free water and malondialdehyde and relative electrical conductivity, and negatively correlated with concentrations of bund water, soluble protein, soluble sugar, starch and proline, but these correlation coefficients were smaller. It seemed likely that accumulated soluble protein, carbohydrate and proline regarding as physiological metabolism and osmore- gulation, participated in regulation of endodomancy induction. Therefore, correlation between physiological changes and respiratory pathways was more complicated.