We investigated the role of the ＂sieve tube-companion cell complex＂ lining the tube periphery, particularly the microfilament and microtubule, in assisting the pushing of phloem sap flow. We made a simple phloem tra...We investigated the role of the ＂sieve tube-companion cell complex＂ lining the tube periphery, particularly the microfilament and microtubule, in assisting the pushing of phloem sap flow. We made a simple phloem transport system with a living radish plant, in which the conducting channel was exposed for local treatment with chemicals that are effective in modulating protoplasmic movement （acetylcholine, （ACh） a neurotransmitter in animals and insects; cytochalasin B, （CB） a specific inhibitor of many cellular responses that are mediated by microfilament systems and amiprophos-methyl, （APM） a specific inhibitor of many cellular responses that are mediated by microtubule systems）. Their effects on phloem transport were estimated by two experimental devices： （i） a comparison of changes in the amount of assimilates in terms of carbohydrates and ^14C-labeled photosynthetic production that is left in the leaf blade of treated plants; and （ii） distribution patterns of ^14C-labeled leaf assimilates in the phloem transport system. The results indicate that CB and APM markedly inhibited the transfer of photosynthetic product from leaf to root via the leaf vein, while ACh enhanced the transfer of photosynthetic product in low concentrations （5.0×10^-4 mol/L） but inhibited it in higher concentrations （2.0×10^-3 mol/L） from leaf to root via the leaf vein. Autoradiograph imaging clearly reveals that ACh treatment is more effective than the control, and both CB and APM treatments effectively inhibit the passage of radioactive assimilates. All of the results support the postulation that the peripheral protoplasm in the sieve tube serves not only as a passive semi-permeable membrane, but is also directly involved in phloem transport.展开更多
Explanations for protoplasmic streaming began with appeals to contraction in the eighteenth century and ended with appeals to contraction in the twentieth. During the intervening years, biologists proposed a diverse a...Explanations for protoplasmic streaming began with appeals to contraction in the eighteenth century and ended with appeals to contraction in the twentieth. During the intervening years, biologists proposed a diverse array of mechanisms for streaming motions. This paper focuses on the re-emergence of contraction among the molecular mecha-nisms proposed for protoplasmic streaming during the twentieth century. The revival of contraction is a result of a broader transition from colloidal chemistry to a macro- molecular approach to the chemistry of proteins, the recognition of the phenomena of shuttle streaming and the pulse of protoplasm, and the influential analogy between protoplasmic streaming and muscle contraction.展开更多
The cell organelles of the coenocytic alga Codium fragile （Sur.） Harlot aggregated rapidly and protoplasts were formed when its protoplasm was extruded out in seawater. Continuous observation showed that there were ...The cell organelles of the coenocytic alga Codium fragile （Sur.） Harlot aggregated rapidly and protoplasts were formed when its protoplasm was extruded out in seawater. Continuous observation showed that there were long and gelatinous threads connecting the cell organelles. The threads contracted, and thus the cell organelles aggregated into protoplasmic masses. The enzyme digestion experiments and Coomassie Brilliant Blue and Anthrone stainings showed that the long and gelatinous threads involved in the formation of the protoplasts might include protein and saccharides as structure components. Nile Red staining indicated that the protoplast primary envelope was non-lipid at first, and then lipid materials integrated into its surface gradually. The fluorescent brightener staining indicated that the cell wall did not regenerate in the newly formed protoplasts and they all disintegrated within 72 h after formation. Transmission electron microscopy of the cell wall of wild C. fragile showed electron-dense material embedded in the whole cell wall at regular intervals. The experiments indicated that C. fragile would be a suitable model alga for studying the formation of protoplasts.展开更多
The extruded protoplasm from the coenocytic green alga,Bryopsis hypnoides Lamouroux,was able to reform a cell wall and develop further into a mature alga in seawater.In this paper,the influence of albumen on the abili...The extruded protoplasm from the coenocytic green alga,Bryopsis hypnoides Lamouroux,was able to reform a cell wall and develop further into a mature alga in seawater.In this paper,the influence of albumen on the ability of aggregation and on the photosynthesis of protoplasm was examined.Results show that the protoplasm of B.hypnoides could aggregate in either albumen or chicken egg,which is similar to that in seawater.However unlike in seawater,the aggregation from B.hypnoides in albumen and chicken egg failed to develop into a mature individual.Interestingly,the protoplasm of B.hypnoides could maintain its photosynthetic O_2 evolution in albumen and chicken egg,while the time in chicken egg was longer than that in albumen.展开更多
基金Supported by the National Natural Science Foundation of China （39470432）.Acknowledgements We thank Cheng-Hou Lou and Richard Dawson （ChinaAgricultural University） for their writing assistance.
文摘We investigated the role of the ＂sieve tube-companion cell complex＂ lining the tube periphery, particularly the microfilament and microtubule, in assisting the pushing of phloem sap flow. We made a simple phloem transport system with a living radish plant, in which the conducting channel was exposed for local treatment with chemicals that are effective in modulating protoplasmic movement （acetylcholine, （ACh） a neurotransmitter in animals and insects; cytochalasin B, （CB） a specific inhibitor of many cellular responses that are mediated by microfilament systems and amiprophos-methyl, （APM） a specific inhibitor of many cellular responses that are mediated by microtubule systems）. Their effects on phloem transport were estimated by two experimental devices： （i） a comparison of changes in the amount of assimilates in terms of carbohydrates and ^14C-labeled photosynthetic production that is left in the leaf blade of treated plants; and （ii） distribution patterns of ^14C-labeled leaf assimilates in the phloem transport system. The results indicate that CB and APM markedly inhibited the transfer of photosynthetic product from leaf to root via the leaf vein, while ACh enhanced the transfer of photosynthetic product in low concentrations （5.0×10^-4 mol/L） but inhibited it in higher concentrations （2.0×10^-3 mol/L） from leaf to root via the leaf vein. Autoradiograph imaging clearly reveals that ACh treatment is more effective than the control, and both CB and APM treatments effectively inhibit the passage of radioactive assimilates. All of the results support the postulation that the peripheral protoplasm in the sieve tube serves not only as a passive semi-permeable membrane, but is also directly involved in phloem transport.
文摘Explanations for protoplasmic streaming began with appeals to contraction in the eighteenth century and ended with appeals to contraction in the twentieth. During the intervening years, biologists proposed a diverse array of mechanisms for streaming motions. This paper focuses on the re-emergence of contraction among the molecular mecha-nisms proposed for protoplasmic streaming during the twentieth century. The revival of contraction is a result of a broader transition from colloidal chemistry to a macro- molecular approach to the chemistry of proteins, the recognition of the phenomena of shuttle streaming and the pulse of protoplasm, and the influential analogy between protoplasmic streaming and muscle contraction.
基金the Project for Supporting the National Development(2006BAD09A04)the Hi-Tech Research and Development (863) Program of China (2006AA05Z112 and 2006AA10A413)grants from the NationalNatural Science Foundation of China (U0633006).
文摘The cell organelles of the coenocytic alga Codium fragile （Sur.） Harlot aggregated rapidly and protoplasts were formed when its protoplasm was extruded out in seawater. Continuous observation showed that there were long and gelatinous threads connecting the cell organelles. The threads contracted, and thus the cell organelles aggregated into protoplasmic masses. The enzyme digestion experiments and Coomassie Brilliant Blue and Anthrone stainings showed that the long and gelatinous threads involved in the formation of the protoplasts might include protein and saccharides as structure components. Nile Red staining indicated that the protoplast primary envelope was non-lipid at first, and then lipid materials integrated into its surface gradually. The fluorescent brightener staining indicated that the cell wall did not regenerate in the newly formed protoplasts and they all disintegrated within 72 h after formation. Transmission electron microscopy of the cell wall of wild C. fragile showed electron-dense material embedded in the whole cell wall at regular intervals. The experiments indicated that C. fragile would be a suitable model alga for studying the formation of protoplasts.
基金Supported by the National Natural Science Foundation of China (No.30830015)the Project of Supporting the National Development (No.2006BAD09A04)and the National High Technology and Development Program of China (863 Program) (Nos.2006AA 10A402,2007AA09Z406,2006AA05Z112,2006AA10A413)
文摘The extruded protoplasm from the coenocytic green alga,Bryopsis hypnoides Lamouroux,was able to reform a cell wall and develop further into a mature alga in seawater.In this paper,the influence of albumen on the ability of aggregation and on the photosynthesis of protoplasm was examined.Results show that the protoplasm of B.hypnoides could aggregate in either albumen or chicken egg,which is similar to that in seawater.However unlike in seawater,the aggregation from B.hypnoides in albumen and chicken egg failed to develop into a mature individual.Interestingly,the protoplasm of B.hypnoides could maintain its photosynthetic O_2 evolution in albumen and chicken egg,while the time in chicken egg was longer than that in albumen.
