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The present work was aimed at understanding and quantifying the effect of sink–source relationships on flower size, using chrysanthemum as a model system. Sink/source ratio was manipulated by flower bud removal (leaving one, two or four flowers, and a control), axillary shoot removal, and varying daily light integral. Furthermore, the influence of flower position within the stem on the flower size was investigated. All means applied to reduce sink/source ratio resulted in a significantly higher individual flower dry mass and area in plants with a fixed number of flowers. Nevertheless, control plants responded to supplementary assimilation light with an increased number of flowers rather than producing larger flowers. Flower position had a negligible effect on flower size in both disbudded and control plants, except that the second-order lateral flowers were significantly smaller than the first-order ones. Singly flowered plants without side shoots represented the greatest potential flower size; they had flowers up to 2.4 times heavier than the control plants. Total aerial plant dry mass was only reduced at very low sink strength treatments, whereas flower mass ratio showed a saturating response to the number of flowers per plant. The results indicate that individual flower size is very sensitive to total plant sink strength, but it does not change with plant source strength when the number of flowers is not manipulated.  相似文献
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A model based on our present knowledge of photosynthetic energy transduction is presented. Calculated electric potential profiles are compared with microelectrode recordings of the thylakoid electric potential during and after actinic illumination periods of intermediate duration. The information content of the measured electric response is disclosed by a comparison of experimental results with calculations. The proton flux through the ATP synthase complex is seen to markedly influence the electric response. Also the imbalance in maximum turnover rate between the two photosystems, common to obligate shade plants like Peperomia metallica used in the microelectrode experiments, is clearly reflected in the electric potential profile.Dedicated to Prof. L.N.M. Duysens on the occasion of his retirement.  相似文献
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The effect of dicyclohexylcarbodiimide (DCCD) on the kinetics of the flashinduced P515 response and on the activity of the ATPase was investigated in isolated spinach chloroplasts. It was found that after the addition of 5×10–8 mol DCCD the rate of ATP hydrolysis induced by a period of 60 sec illumination was decreased to less than 5% of its original value. At this concentration, hardly any effect, if at all, could be detected on the kinetics of the flash-induced P515 response, neither in dark-adapted nor in light-activated chloroplasts. It was concluded that the presence of concentrations of DCCD, sufficiently high to affect the ATPase activity, does not affect the kinetics of the flash-induced P515 response. Since DCCD decreases the H+ permeability of the membrane-bound ATPase, it was concluded that this permeability coefficient for protons is not an important factor in the regulation of the flash-induced membrane potential and, therefore, does not affect the kinetics of the flash-induced P515 response.  相似文献
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Background  

The xylem vascular system is composed of fused dead, hollow cells called tracheary elements (TEs) that originate through trans-differentiation of root and shoot cambium cells. TEs undergo autolysis as they differentiate and mature. The final stage of the formation of TEs in plants is the death of the involved cells, a process showing some similarities to programmed cell death (PCD) in animal systems. Plant proteases with functional similarity to proteases involved in mammalian apoptotic cell death (caspases) are suggested as an integral part of the core mechanism of most PCD responses in plants, but participation of plant caspase-like proteases in TE PCD has not yet been documented.  相似文献
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