Background information. Cadmium (Cd) is a highly toxic heavy metal that causes changes in plant metabolism through inhibiting photosynthesis and respiration. The effects of Cd on the morphology and function of the chloroplast and mitochondria, as well as on the production and localization of ROS (reactive oxygen species), were studied at the single-cell level in Arabidopsis.Results. The present study showed that the morphology of chloroplasts changed after Cd treatment, and the photochemical efficiency dramatically declined prior to obvious morphological distortion in the chloroplasts. A quick burst of ROS was detected after Cd treatment. The ROS appeared first in the mitochondria and subsequently in the chloroplast. Simultaneously, the mitochondria clumped irregularly around the chloroplasts or aggregated in the cytoplasm, and the movement of mitochondria was concomitantly blocked. Furthermore, the production of ROS was decreased after pre-treatment with ascorbic acid or catalase, which prevented inhibition of photosynthesis, organelle changes and subsequent protoplast death. Our results suggest that the distribution and mobility of mitochondria, the morphology of chloroplasts and the accumulation of ROS play important roles in Cd-induced cell death. The results are in good agreement with previous reports of many types of apoptotic-like cell death.Conclusion. The changes in the distribution and mobility of mitochondria, and morphology of chloroplasts, as well as the accumulation of ROS, play important roles in Cd-induced cell death.

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Gerbera hybrida (Shenzhen No.5) seedlings' inflorescence development was divided into six stages (P1-P6). With these six stages petal, delayed luminescence (DL) were observed during petal development using lab-made detector system, fluorescence spectrum and confocal imaging were also observed. The results showed that the intensity of DL were increased during P1-P4 and decreased in P5 and P6; with the excitation wavelength of 488 nm, fluorescence spectra were obviously different during P1-P6 stages; imaging of chlorophyll autofluorescence by confocal laser scanning microscopy (CLSM) showed that the intensity were stronger in P3 than in P1, while P6 stage autofluorescence only displayed in guard cell of epidermis. Our results suggested that the DL technique, combining with fluorescence spectra and CLSM imaging, might be useful for the rapid and noninvasive evaluation of chlorophyll content and degradation in petal development in Gerbera hybrida.