Photosynthetic Phisiology Prohibition And Cell Pathology Studies On Bean Broad Wilt Virus-infected Host Plants

Bean broad wilt virus 2(BBWV 2) is reported in many regions of China, caused serious loses in economic crops. In this paper, the ultrastructural alteration of two host plants respectively infected with isolates of BBWV were systemically studied by transmission electron microscope (TEM). And the physiological mechanism of restrained photosynthesis induced by BBWV was investigated by photosynthetic and fluorescent technique. Furthermore, the system of plant protoplasts invested by PLCV was established.1. Wither symptoms occurred on the leaves of Vicicafaba inoculated with the B935 isolate, P158 isolate and PV131 isolate of BBWV2.The typical mosaic symptoms occurred on the leaves of Chenopodium quinoa inoculated with the three isolates of BBWV2 and leaves of V.faba inoculated with NSRV1 isolate of BBWV1. Under the TEM, two main ultrastructural changes were observed in the thin sections of the infected leaves of V.faba and C. quinoa: (1) virus-form tubular structures in diameter were formed of 17-19 virus-like particles in the leaves infected by B935, while this tubular structures were formed of 9 virus-like particles in the leaves infected by other isolates of BBWV.Secong, chloroplasts were disrupted in the infected cells of V.faba leaves. Most of the B935-infected chloroplasts showed inhibition of lamellar development or membrane vesiculation and the other isolates infected chloroplasts showed swollen or disintegrated membrane.2. The effects of BBWV 2 isolates B935,P158 and PV131 infection on photosynthetic activities, fluorescence emission spectras at 77K and chloroplast ultrastrucrure in host plants were investigated. As the disease progressed, net photosynthetic rate (P_n), stomatal conductance (G_s) of leaves, the chlorophyll content and chlorophyll a/b ratio decreased while the intercellular CO2 concentration (c₁) of leaves rose in comparison with that of the healthy plants. After BBWV 2 infection, Fv / Fm Fy' / Fm' ΦpsII and qp values all became lower, but the NPQ values were higher than the healthy control plants. The fluorescence emission spectras at 77K indicated that infected leaves had higher F686/F734 values and shifted peaks from those of normal ones. The datas may conclude that the infection inhibited mainly the PS II activity and the energy distribution between PS II and PS I was affected at the same time. The values also showed that PV131 infection caused greater changes on these parameters than the other two isolates. This difference may caused by their different nosogensis.3. Callus were induced from baccy leaves to acquire cells cultured in liquid medium. Then protoplasts were abrupted separately from the leaves and the callus. Then better methods to establish the virus-infected protoplasts system were disgust. On the other hand, the microtubule pattern was revealed by means of immunoblotting in the protoplast. Eximious method were chosen to do the further investigation.