Study On Physiological And Biochemical Mechanism Of Plastids During Early Stage Of Seedling De-etiolation Of Phaseolus Radiatus L.

It is important to study on the developing of the plastids in the field of plant photobiology, and it is significant to elaborate mechanism of the chloroplasts biogenesis. In order to elaborate the physiological and biochemical reaction, changes of light signal and regulatory mechanism between plastids and nucleus, we took Phaseolus radiatus L. as experimental material and used many methods such as continuous illumination, flash light and antibiotics control the development of the P. radiatus. Moreover, combining with spectral technique, gel electrophoresis and electron microscope, we investigated the photoreduction of protochlorophyllide (Pchlide), the biosynthesis of chlorophyll (Chi), the activity of photosystem, the assembly of pigment protein complexes, the changes of absorption spectrum and fourth derivatives spectra, the changes of Chi fluorescence kinetics, the formation of P700, and the ultrastructure of chloroplast. The main conclusions are as follows:1. Taking etiolated seedling of P. radiatus as experimental material, we treated the etiolated seedling using monochromatic light of different wavelengths (472nm, 628nm and 655nm), white light and antibiotics. In the condition of continuous illumination and flash light (750ms), we measured the photoreduction of Pchlide and the changes of Chi content in the course of leaf development of seedling. The results showed that in the reduction course of Pchlide from etiolated seedling of P. radiatus, the absorption of light energy is react substrate Pchlide itself. The Pchlide is a primal photoreceptor. The continuous illumination can improve the biosynthesis rate of Pchlide. The flash light can induce the reduction of Pchlide, but the function of the biosynthesis of Pchlide is of little affected. At the initial stage of de-etiolation of seedling leaves (illumination <4 hours), the monochromatic light is beneficial to biosynthesis of Chi, in the later stage of seedling development (illumination > 36 hours), the monochromatic light is not beneficial to the biosynthesis of Chi and seedling growth. The reduction of Pchlide and the fastesterification of chlorophyllide (Chlide) are free from regulation of plastid and nucleus, but the slow esterification of Chlide is controlled by nucleus.2. Under different duration and intensity of illumination, we measured and analyzedthe absorption spectrum and fourth derivatives spectra of seedling leaves of the P. radiatus with micro fiber spectrometer under room temperature. The etiolated leaves of the P. radiatus seedlings had three absorption peaks, 628nm, 638nm and 652nm, respectively. Illumination of 1 μmol.m-2.s-1 light intensity can induce the reduction of photoactive Pchlide to Chlide; Within 10s illumination (20μmol.m-2.s-1), the main physiological and biochemical changes of seeding leaves include the reduction of photoactive Pchlide to Chlide (absorption peak in 690nm and 672nm), and the fast esterification of Chlide into Chi a. Afterwards illumination of 20s (20μmol.m-2.s-1), the most photoactive Pchlide transformed into Chlide. For 1 min of continuous illumination, nonphotoactive Pchlide combines with POR protein and shaped new photoactive Pchlide.3. Using oxygen electrode to measure the photosynthetic rate of leaves and the activity of membrane proteins, the etiolation leaves of seedling were treated with monochromatic light, white light and antibiotic. The membrane proteins of leaves were separated with gel electrophoresis. It showed that the membrane proteins of plastids presented obvious activities and the seeding leaves showed obvious activities of releasing oxygen after 4h of continuous illumination. For the less proteins accumulated it cannot be examined by gel electrophoresis, the bands of gel electrophoresis of the pigment protein complexes appeared lately. The monochromatic light has more physiological activity than white light. In the formatting course of PSI and Lhc, the plastids have little function, which is mainly regulated by nucleus gene expression.4. Using PAM-2100 chlorophyll fluorometer, we meas...