Effect Of High Temperature Stress On Electrical Impedance Spectroscopy Parameters And Chlorophyll Fluorescence Characteristics Of Chrysanthemum

This research used the white chrysanthemum varieties ’ Jinba ’ ( Dendranthema grandiflora ’ Jinba ’ ) as test material, with the conditions of high temperature stress, it could study in following several aspects: the electrical impedance spectroscopy (EIS) parameters of chrysanthemum under high temperature stress, the kinetic parameters change of chlorophyll fluorescence and the response of the peroxidation defense system of chrysanthemum leaves under high temperature stress and other aspects of research. The main research results as follows:1. The study showed that the influence of the electrical impedance spectroscopy (EIS) parameters under high temperature stress. Extracellular resistance of chrysanthemum stems did not change significantly in the 25 ~ 40℃, it increased significantly when the temperature reached 45℃, and then decreased sharply. In the 25 ~ 45℃, with temperature increasing, the intracellular resistance increased irregularly and decreased sharply beyond 45℃. Extracellular resistance of chrysanthemum leaves increased sharply in the 30℃, before the temperature reached 45℃, it did not change any more, and it’s higher than the extracellular resistance when the temperature was 25℃, then it decreased sharply beyond 45℃. With the intracellular resistance of chrysanthemum leaves firstly increased and then decreased with temperature increasing. The trend of relaxation time of stems and leaves showed an irregularly change: increased-decreased-increased-decreased. The distribution coefficient of relaxation time changed slightly, the change of the stems was greater than the leaves. This showd that the change of the electrical impedance spectroscopy parameters had close contact with the physiological structure of the cell.2. Under high temperature stress, with increasing temperature, the chrysanthemum leaf conductivity, proline content and MDA content showed a upward– downward- upward trend, SOD activity, soluble protein content showed a drop - upward - downward trend, but the activity of POD change slightly. It showed that in the early when the temperature increased, the injury caused by high temperature stress could be reduced by autoregulation of the chrysanthemum, but as the temperature stress gone higher, this ability was gradually reduced.3. Under high temperature stress, the relative conductivity of the stems had significant negative correlation with extracellular resistance, and the relaxation times showed significant negative correlation(r=0.94, 0.92). However, the change of the relative conductivity of the leaves had great negative correlation with the intracellular resistance, the extracellular resistance and the relaxation time(r=0.89, 0.88, 0.89). There was significant negative correlation between the proline content and the relaxation times(r=0.98, 0.99), and it had negative correlation with the intracellular resistance(r=0.94). The SOD activity of leaves of chrysanthemum had no significant correlation with the electrical impedance spectroscopy parameters. The activity of POD had great negative correlation with the extracellular resistance and the intracellular resistance (r=0.96, 0.93). There was on significant negative correlation between soluble protein content and the electrical impedance spectroscopy parameters. In sum, the extracellular resistance and the relaxation times were suitable for determining the heat resistance of chrysanthemum with the electrical impedance spectroscopy parameters, and the extracellular resistance was the most suitable parameter. It showed that compared with other electrical impedance spectroscopy parameters, the extracellular resistance indicated the heat resistance of the samples better.4. With the temperature increasing, the chrysanthemum leaf chlorophyll fluorescence parameters Fo, qN, Y(NPQ), Y(NO) showed irregular upward trend. qP, Fv/Fm,ΦPSII and ETR value showed irregular decline. The changes of chlorophyll fluorescence under high temperature showed that the optical system of the chrysanthemum was injured by high temperature, the luminous energy absorption and transmission efficiency was lowered, and heat dissipation increases, thus affect the photosynthetic electron transfer process and photophosphorylation.