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991.
红壤旱坡地桔园覆盖的生态效应及经济效益评价 总被引:11,自引:2,他引:9
柑桔是南方红壤地区栽培的主要果树种类,栽培面积达1126×106hm2。柑桔是一种常绿果树,生长量大,挂果期长,周年需要消耗大量的水分。我国南方红壤地区虽然雨水充沛,但降水季节分布不均,柑桔果实迅速生长的7~10月正是该地区雨水少、蒸发量大的伏秋干旱季节。经常性的伏秋干旱是制约我国柑桔产量和质量进一步提高的主要障碍因素之一。桔园夏秋进行秸秆覆盖可以降温[1]、保水[2]、防止杂草生长[3]等,但桔园应用地膜覆盖及常年连续覆盖对桔园的生态效应方面的研究较少,为此我们开展了这方面的工作,并通过连续3a的产量及产值分析覆盖桔园的经… 相似文献
992.
北方稻田生态系统水量平衡及水分效率研究 总被引:15,自引:8,他引:7
1993~1995年研究了5种不同模式水稻田生态系统水量平衡及水分效率结果表明,不同水稻田模式其总耗水量之间有明显差异,其中节水模式和节水节肥模式较常规模式节省灌溉水达15~23%,水分生产效率增加30%以上.各模式蒸发蒸腾耗水量在同一生长季内基本相同.田间结构及调控管理对其无明显影响实测水稻生育期田间蒸发蒸腾量与计算的可能蒸发蒸腾量相差不过5%。 相似文献
993.
994.
995.
水稻叶片对模拟酸雨伤害的生理反应 总被引:4,自引:0,他引:4
水稻暴露于pH2.5~4.2的模拟酸雨中2个月后测定表明:叶片叶绿素含量下降,细胞液离子外渗率增加,气孔阻抗增高,蒸腾速率降低。不同叶位的水稻叶片对模拟酸雨的敏感性不同,杂交稻(汕优63)对模拟酸雨的敏感性较粳稻(中粳864)高 相似文献
996.
Primary cell cultures were prepared from a major neurosecretory center of the adult locust brain, the pars intercerebralis, in order to characterize neurosecretory cells growingin vitro. Individual pars intercerebralis could be removed free of surrounding tissue and dissociated by mechanical treatment. Mature neurosecretory neurons of different sizes regenerate new neurites during the initial three daysin vitro in serum-free medium. They show a tendency to sprout one primary neurite from which fine processes develop. By means of electron microscopy, we observed the integrity of the cellular organelles, indicating that cultured neurons are healthy, and we were able to distinguish three types of neurosecretory neurons on the basis of the ultrastructural aspects of the neurosecretory material. These three types have the same ultrastructural characteristics asin situ neuroparsin, ovary maturing parsin and locust insulin related peptide neurons. Immunogold labelling at the electron microscopic level, using the two available specific antibodies, anti-neuroparsin and anti-ovary maturing parsin, confirms the morphological characterization of neuroparsin and ovary maturing parsin cells. These results show for the first time that cultured locust neurosecretory neurons behave like thosein vivo, in terms of their ultrastructure and immunocytochemistry. Moreover, the presence of recently-formed neurosecretory material both in the Golgi zone of the perikaryon and in the neuronal processes indicates that cultured neurons have functional capacity since they are able to synthesizede novo and to transport the neurosecretory material along the neurite. Thus our well-characterized culture system provides a suitable invitro model to investigate the secretory mechanism of locust neurosecretory neurons. 相似文献
997.
M. Ghirardi A. Casadio L. Santarelli P. G. Montarolo 《Invertebrate neuroscience : IN》1996,2(1):41-49
Hemolymph of adultAplysia californica significantly affects neurite outgrowth of identified neurons of the land snailHelix pomatia. The metacerebral giant cell (MGC) and the motoneuron C3 from the cerebral ganglion and the neuron B2 from the buccal ganglion
ofH. pomatia were isolated by enzymatic and mechanical dissociation and plated onto poly-l-lysine-coated dishes either containing culture medium conditioned byHelix ganglia, or pre-treated withAplysia hemolymph. To determine the extent of neuronal growth we measured the neurite elongation and the neuritic field of cultured
neurons at different time points.Aplysia hemolymph enhances the extent and rate of linear outgrowth and the branching domain ofHelix neurons. With the hemolymph treatment the MGC neuron more consistently forms specific chemical synapses with its follower
cell B2, and these connections are more effective than those established in the presence of the conditioned medium. 相似文献
998.
The accessibility of embryonic and adult neurons within invertebrate nervous systems has made them excellent subjects for
neurobiological study. The ability to readily identify individual neurons, together with their great capacity for regeneration,
has been especially beneficial to investigations of synapse formation and the specificity of neuronal connectivity. Many invertebrate
neurons survive for long periods following isolation into primary cell culture. In addition, they readily extend new neuritic
arbors and form electrical and chemical connections at sites of contact. Thus, cell culture approaches have allowed neuroscientists
greater access to, and resolution of, events underlying neurite outgrowth and synaptogenesis. Studies of identified neuromuscular
synapses ofHelisoma have determined a number of signaling mechanisms involved in transsynaptic communication at sites of neuron-target contact.
At these sites, both anterograde and retrograde signals regulate the transformation of growth cones into functional presynaptic
terminals. We have found that specific muscle targets induce both global and local changes in neurotransmitter secretion and
intracellular calcium handling. Here we review recent studies of culturedHelisoma synapses and discuss the mechanisms thought to govern chemical synapse formation in these identified neurons and those of
other invertebrate species. 相似文献
999.
Shur-Jen Wang Peter Greer Robert Auerbach 《In vitro cellular & developmental biology. Animal》1996,32(5):292-299
Summary We report on the isolation and propagation of endothelial cells from the mouse embryonic yolk sac, the earliest site of blood
vessel development, and on the advantages of a hypervascular transgenic mouse source of these cells. These transgenic mice
express multiple copies of an activated allele of the humanfps/fes proto-oncogene and display hypervascularity progressing to multifocal hemangiomas. This phenotype suggested a role of thefps/fes proto-oncogene in vasculogenesis and angiogenesis and led us to investigate the growth characteristics of yolk-sac-derived
endothelial cells from transgenicfps/fes embryos. We have established eight independent cell clones from a mixture of transgenic and control yolk sacs from Day 12
embryos. Southern blot hybridization analysis showed all eight clones to be derived from transgenic cells suggesting a growth
advantage of cells carrying the activatedfps/fes gene. A cell line, Clone 166 (C166), established from one of these clones, was more fully characterized. C166 exhibits normal
endothelial characteristics, such as rearrangement into tubelike structures when placed on Matrigel, expression of angiotensin
converting enzyme, retention of cobblestone morphology at confluence, and the presence of cell surface receptors for acetylated
low density lipoprotein. The cells constitutively express murine endothelial cell adhesion molecule VCAM-1 and the vascular
addressin identified by antibody MECA-99. As expected, the cell line expresses high levels of the cytoplasmic protein-tyrosine
kinase encoded by thefps/fes proto-oncogene. The clone we have described as well as other endothelial cell lines that we have established from the mouse
embryonic yolk sac should prove useful for the study of endothelial cell differentiation and for the determination of the
mechanisms underlying the establishment of organ-specific endothelial cell heterogeneity. 相似文献
1000.
Summary Techniques for the isolation of ahhighly pure population of viable osteoclasts are limited. For this reason, we developed
an isolation procedure that results in a high yield of osteoclast-like cells, up to 92% pure, from 3-wk-old chicken tibias.
The unique feature of the method is the migration of cells from marrow-free endosteal surfaces to vitronectin-coated plates.
The cells retain the osteoclast phenotype and remain viable in culture for a minimum of 1 wk. The cells were characterized
and compared to two populations of authentic avian osteoclasts, which were isolated on the basis of association with fibronectin-coated
plates. The cells contained substantial amounts of tartrate-resistant acid phosphatase. Alkaline phosphatase levels were negligible,
suggesting little contamination by osteoblasts. Response to parathyroid hormone, dibutyryl cyclic adenosine monophosphate,
calcitonin, acetazolamide, 17β-estradiol, and prostaglandin E2 was evident, as detected by measuring acid production. The vitronectin-associating cells contained numerous mitochondria,
had the ability to resorb bone in anin vitro bone slice assay, and specifically bound biotinylated vitronectin. At 5 d of culture, the cells demonstrated marginal multinuclearity,
having two to three nuclei. A large number (∼1×106 cells/tibia) of viable cells that exhibit characteristics of authentic osteoclasts can be obtained by the method described.
Potentially, this method could be applied to other species. 相似文献