Studies On Structure And Photosynthetic Activity Of Plastids In Garlic Scape

To investigate the structure and photosynthetic activity of the plastids in each tissue area of different color segments in garlic scape,in this paper,the distribution,morphology and ultrastructure of plastids were observed by means of freehand sectioning,microscopy and electron microscopy,and photosynthetic pigment content,photosynthetic rate,optical properties,fourth derivative spectrum,chlorophyll fluorescence parameters and light response curve of plastids were studied at organ,tissue and molecular levels with spectrophotometry,gas exchange,optical fiber spectroscopy and chlorophyll fluorescence technology,in order to provide valuable clues to understand physiological and ecological functions,and the roles in the development,storage and preservation of the plastids from garlic scape.The results were as follows:(1)The plastids were distributed in 4-5 layers of parenchyma cells in the cortex and 1-2 layers of parenchyma cells on the outside of each whorl of vascular bundle in garlic scape,and the plastids in different color segments and tissue areas of garlic scape were different in morphology and structure.(2)Among the color segments,the sequence of chlorophyll a(Chl.a),chlorophyll b(Chl.b)and carotenoid(Car.)content was green segment>color conversion segment>yellow segment;in different tissue areas of the same color range,the content order of Chl.a and Chl.b was cortex>the first whorl vascular bundle>the second whorl vascular bundle>the third whorl vascular bundle,however,the order of Car.content was the third round of vascular bundle>the second round of vascular bundle>the first round of vascular bundle>cortex.(3)In the range of 400 nm-800 nn,the order of reflectance and transmittance in different color and tissue areas was the third whorl of vascular bundle>the second whorl of vascular bundle>the first whorl of vascular bundle>cortex,while the order of absorption rate was opposite.(4)The absorption peaks of the photosynthetic proteins PSI,LHCII and Cytb559 were redshifted or blue-shifted 1-5 nm in the fourth derivative spectra of the tissue areas in different color segments.(5)Among each tissue ares of the different color segments,the order of the actual photochemical efficiency(Y(?)),the photochemical quenching(qP)and the electron transfer efficiency(ETR)was cortex>first whorl vascular bundle>second whorl vascular bundle>third whorl vascular bundle,But the order of NPQ was opposite.The difference between the cortex and the vascular bundles F0,F,,Fv/Fm,Fv/F0 reached an extremely significant level.These results suggested that the plastids structure and photosynthetic activity of various tissue areas in different color sections of the garlic scape were significantly differentiated.