Acetylcholine (Ach) is a key component of animal cholinergic system. Recent experiments demonstrated that Ach, choline acetyltransferase, acetylcholinesterase and Ach receptors are present in all parts of plants and...Acetylcholine (Ach) is a key component of animal cholinergic system. Recent experiments demonstrated that Ach, choline acetyltransferase, acetylcholinesterase and Ach receptors are present in all parts of plants and have many functions, including inducing stomatal movement. The authors' previous work has evidenced that microtubules and microfilaments are involved in regulating both stomatal closing and opening. The present investigation is to determine whether stomatal opening induced by Ach is associated with microtubules and microfilaments. The results showed that Ach could induce stomatal opening of Vicia faba L. with or without addition of KCl in the dark. Ach also stimulated protoplast swelling in a K +_free solution in the dark. However, the induction was partially suppressed when the strips and protoplasts were pretreated with either cytochalasin B, an inhibitor of F_actin polymerization, or oryzalin, an inhibitor of plant microtubule polymerization. Thus, our data suggest for the first time that stomatal opening induced by Ach is associated with the dynamics of microtubules and microfilaments.展开更多
Since nuclear extrusion was rediscovered in young Allium scale by S.H.WU in the years of 1950's systematic investigations on this phenomenon were carried out with various kinds of microscopic techniques a...Since nuclear extrusion was rediscovered in young Allium scale by S.H.WU in the years of 1950's systematic investigations on this phenomenon were carried out with various kinds of microscopic techniques and plant materials to collect more effective evidence to clarify the debate about whether the nuclear extrusion is an artifact or normal event. In the cooperative research of S. H. WU and C. H. LOU the normality of the occurrence of nuclear extrusion either in growing part of plant or in senescent tissue has been confirmed. This event is intimately associated with the physiological state of the tissues/cells and may play an important role in redistribution and reutilization of cell contents. Based on the results obtained a hypothesis of intercellular movement of protoplasm as a means of translocation of organic material in plants was suggested. Chromatin extrusion was also discovered in the pollen mother cells (cytomixis) of certain angiosperms by G. C. ZHENG and his team. Intercellular migration of chromatin appears most frequently at the stage of synizesis. Cytomixis has been studied in relation to variation and evolution. Chromosome aberration has been considered to be closely associated with chromatin extrusion. By vital microscopic observations of the live tissues of garlic (Allium sativum L.) bud and wheat (Triticum aestivum L.) ovule combined with cinemicroscopy and video recording it has been uncovered that, not only the nuclear material but also the cytoplasm could traverse the intercellular channels by vigorous contraction and expansion, and they may simultaneously extrude out of a cell but often asynchronously migrate from one cell to another. The involvement of cytoplasmic constituents in intercellular migration was also detected in pollen mother cells with electron microscopy. Regarding the mechanism of intercellular movement a series of experiments provide convincing evidence showing that this kind of movement is an active metabolic process closely coupled with energy metabolism, and the motive power for driving the extrusion may be supplied by the contractile proteins in protoplasm.展开更多
The steel wire rope of continuous conveyor with disc-tube assembly is droved by the driving wheel. When the driving wheel rotates, the gear is combined to the con- nection disc in turn, promoting the connection disc t...The steel wire rope of continuous conveyor with disc-tube assembly is droved by the driving wheel. When the driving wheel rotates, the gear is combined to the con- nection disc in turn, promoting the connection disc to move in succession. Turning the whirling torque of driving wheel into the straight-line traction force. When the steel wire rope is winded by the driving wheel some winded along the circumference, others winded along the straight line. Used motion subject law, this article analyses the change of the velocity and the acceleration of the steel wire rope in the straight movement, and observe the mathematics’ model of velocity and acceleration.展开更多
Plasmodesmata (PDs) are cytoplasmic structures that link adjacent cells to form the symplast of a plant. PDs are involved extensively in a plant's life by mediating symplastic transport of a wide range of ions and...Plasmodesmata (PDs) are cytoplasmic structures that link adjacent cells to form the symplast of a plant. PDs are involved extensively in a plant's life by mediating symplastic transport of a wide range of ions and molecules. Major components of a plasmodesma (PD) include a plasma membrane, a desmotubule, and a cytoplasmic annulus, all of which are readily detectable by electron microscopy. Both the plasma membrane and the desmotubule contain proteinaceous particles, thought to be involved in altering the size of the cytoplasmic annulus. Cytoskeleton elements (actin and myosin) are essential for maintaining the integrity of PDs. Together with these elements, calcium_binding proteins probably play a significant role in regulating PD function. Symplastic transport occurs through the cytoplasmic annulus for the great majority of solutes, while other substances may traverse through the desmotubule internal compartment, the desmotubule shell, or the plasma membrane. The symplast is subdivided into several domains with varying molecular size exclusion limits (ranging from <1 kD to >10 kD). Plasmodesmata can be either primary or secondary; the former are developed during new wall formation and the latter are made in existing walls. The dynamic nature of plasmodesmata is also reflected by their changing frequencies, which, in turn, depend on the developmental and physiological status of the tissue or the entire plant. While diffusion is the major mechanism of symplastic transport, plasmodesmata are selective for certain ions and molecules. Upon viral infection, viral movement proteins interact with PD receptor proteins and, as a result of yet unknown mechanisms, the plasmodesmata are remarkably dilated to allow viral movement proteins and the bound viral genome to enter healthy cells. Some proteins of plant origin are also able to traverse plasmodesmata, presumably in ways similar to viral movement proteins. Some of these plant proteins are probably signal molecules contributing to cell differentiation and other activities. Other proteins move cell_to_cell in a non_specific manner.展开更多
The tourist industry, as global mass phenomenon, is inextricably linked to the evolution of air transport systems and air carriers, in turn, depends on tourism to ensure stability in routes and prices. Therefore, both...The tourist industry, as global mass phenomenon, is inextricably linked to the evolution of air transport systems and air carriers, in turn, depends on tourism to ensure stability in routes and prices. Therefore, both sectors must face the new challenges together, the transport industry is heading a problem of energy and cost overruns, that inevitably will affect tourism in the short term. The first energy crisis that they are starting to live, has been mitigated by changes in three parameters： （1） the international regulation of commercial aviation; （2） the connectivity and business （birth of low cost companies） models; and （3） the new policies for climate change and gas emission. So far, the rapid growth of the tourist industry has being held on a fast and cheap access to transport energy resources based on the false belief of unlimited access to energy. The article is a review of the state of the art, and the research papers published on air transportation, relating to tourism and the emergence of low cost airlines, in order to give a global vision for the decision makers of mass destinations, as it is the case of the Canary Islands that we will use as a reference.展开更多
文摘Acetylcholine (Ach) is a key component of animal cholinergic system. Recent experiments demonstrated that Ach, choline acetyltransferase, acetylcholinesterase and Ach receptors are present in all parts of plants and have many functions, including inducing stomatal movement. The authors' previous work has evidenced that microtubules and microfilaments are involved in regulating both stomatal closing and opening. The present investigation is to determine whether stomatal opening induced by Ach is associated with microtubules and microfilaments. The results showed that Ach could induce stomatal opening of Vicia faba L. with or without addition of KCl in the dark. Ach also stimulated protoplast swelling in a K +_free solution in the dark. However, the induction was partially suppressed when the strips and protoplasts were pretreated with either cytochalasin B, an inhibitor of F_actin polymerization, or oryzalin, an inhibitor of plant microtubule polymerization. Thus, our data suggest for the first time that stomatal opening induced by Ach is associated with the dynamics of microtubules and microfilaments.
文摘Since nuclear extrusion was rediscovered in young Allium scale by S.H.WU in the years of 1950's systematic investigations on this phenomenon were carried out with various kinds of microscopic techniques and plant materials to collect more effective evidence to clarify the debate about whether the nuclear extrusion is an artifact or normal event. In the cooperative research of S. H. WU and C. H. LOU the normality of the occurrence of nuclear extrusion either in growing part of plant or in senescent tissue has been confirmed. This event is intimately associated with the physiological state of the tissues/cells and may play an important role in redistribution and reutilization of cell contents. Based on the results obtained a hypothesis of intercellular movement of protoplasm as a means of translocation of organic material in plants was suggested. Chromatin extrusion was also discovered in the pollen mother cells (cytomixis) of certain angiosperms by G. C. ZHENG and his team. Intercellular migration of chromatin appears most frequently at the stage of synizesis. Cytomixis has been studied in relation to variation and evolution. Chromosome aberration has been considered to be closely associated with chromatin extrusion. By vital microscopic observations of the live tissues of garlic (Allium sativum L.) bud and wheat (Triticum aestivum L.) ovule combined with cinemicroscopy and video recording it has been uncovered that, not only the nuclear material but also the cytoplasm could traverse the intercellular channels by vigorous contraction and expansion, and they may simultaneously extrude out of a cell but often asynchronously migrate from one cell to another. The involvement of cytoplasmic constituents in intercellular migration was also detected in pollen mother cells with electron microscopy. Regarding the mechanism of intercellular movement a series of experiments provide convincing evidence showing that this kind of movement is an active metabolic process closely coupled with energy metabolism, and the motive power for driving the extrusion may be supplied by the contractile proteins in protoplasm.
基金Supported by Education Office of Liaoning Province (20081218)
文摘The steel wire rope of continuous conveyor with disc-tube assembly is droved by the driving wheel. When the driving wheel rotates, the gear is combined to the con- nection disc in turn, promoting the connection disc to move in succession. Turning the whirling torque of driving wheel into the straight-line traction force. When the steel wire rope is winded by the driving wheel some winded along the circumference, others winded along the straight line. Used motion subject law, this article analyses the change of the velocity and the acceleration of the steel wire rope in the straight movement, and observe the mathematics’ model of velocity and acceleration.
文摘Plasmodesmata (PDs) are cytoplasmic structures that link adjacent cells to form the symplast of a plant. PDs are involved extensively in a plant's life by mediating symplastic transport of a wide range of ions and molecules. Major components of a plasmodesma (PD) include a plasma membrane, a desmotubule, and a cytoplasmic annulus, all of which are readily detectable by electron microscopy. Both the plasma membrane and the desmotubule contain proteinaceous particles, thought to be involved in altering the size of the cytoplasmic annulus. Cytoskeleton elements (actin and myosin) are essential for maintaining the integrity of PDs. Together with these elements, calcium_binding proteins probably play a significant role in regulating PD function. Symplastic transport occurs through the cytoplasmic annulus for the great majority of solutes, while other substances may traverse through the desmotubule internal compartment, the desmotubule shell, or the plasma membrane. The symplast is subdivided into several domains with varying molecular size exclusion limits (ranging from <1 kD to >10 kD). Plasmodesmata can be either primary or secondary; the former are developed during new wall formation and the latter are made in existing walls. The dynamic nature of plasmodesmata is also reflected by their changing frequencies, which, in turn, depend on the developmental and physiological status of the tissue or the entire plant. While diffusion is the major mechanism of symplastic transport, plasmodesmata are selective for certain ions and molecules. Upon viral infection, viral movement proteins interact with PD receptor proteins and, as a result of yet unknown mechanisms, the plasmodesmata are remarkably dilated to allow viral movement proteins and the bound viral genome to enter healthy cells. Some proteins of plant origin are also able to traverse plasmodesmata, presumably in ways similar to viral movement proteins. Some of these plant proteins are probably signal molecules contributing to cell differentiation and other activities. Other proteins move cell_to_cell in a non_specific manner.
文摘The tourist industry, as global mass phenomenon, is inextricably linked to the evolution of air transport systems and air carriers, in turn, depends on tourism to ensure stability in routes and prices. Therefore, both sectors must face the new challenges together, the transport industry is heading a problem of energy and cost overruns, that inevitably will affect tourism in the short term. The first energy crisis that they are starting to live, has been mitigated by changes in three parameters： （1） the international regulation of commercial aviation; （2） the connectivity and business （birth of low cost companies） models; and （3） the new policies for climate change and gas emission. So far, the rapid growth of the tourist industry has being held on a fast and cheap access to transport energy resources based on the false belief of unlimited access to energy. The article is a review of the state of the art, and the research papers published on air transportation, relating to tourism and the emergence of low cost airlines, in order to give a global vision for the decision makers of mass destinations, as it is the case of the Canary Islands that we will use as a reference.
