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91.
黄土丘陵区植被恢复对深层土壤有机碳的影响 总被引:10,自引:1,他引:10
以恢复9、15、24a和34a的刺槐林为研究对象,探究黄土丘陵区深层土壤有机碳(SOC)积累以及对植被恢复的响应。区域深层土壤(50-200cm)SOC含量高达1.35-2.39g·kg-1,约为浅层土壤(0-50cm)SOC含量的25%;深层土壤SOC储量高达26.28-46.50t.hm-2,占2m土层SOC储量的50%以上,显著高于浅层SOC储量;植被恢复20多年后与恢复9a相比,深层SOC含量和储量都有极显著提高。2m土层SOC含量随植被恢复20多年后较9a提高1倍左右;2m土层SOC储量增幅为43.02.thm-2(9-34a),明显高于1m土层SOC储量增幅34.65t.hm-2(9-34a)。浅层土壤中的0-30cm相邻土层间SOC含量差异显著,而深层SOC含量较稳定。深层SOC含量与刺槐盖度、基径、高度呈极显著正相关。在评价黄土丘陵区植被恢复的土壤固碳效应时应充分考虑深层土壤有机碳储量和变化。 相似文献
92.
Our findings suggest that nitric oxide (NO) acts as peripheral neuromodulator in locusts, in which it is commonly co-localized with RF-like peptide in neurosecretory cells. We also present the first evidence for NO as a cardio-regulator in insects. Putative NO-producing neurones were detected in locust pre-genital free abdominal ganglia by NADPH-diaphorase histochemistry and with an antibody against NO synthase (NOS). With both methods, we identified the same 14 somata in each examined ganglion: two dorsal posterior midline somata; six ventral posterior midline somata; and three pairs of lateral somata. A combination of NOS-detection methods with nerve tracing and transmitter immunocytochemistry revealed that at least 12 of these cells were efferent, of which four were identified as peptidergic neurosecretory cells with an antiserum detecting RFamide-like peptides. One of the latter was unequivocally identified as an octopaminergic dorsal unpaired median (DUM) neurone, which specifically projected to the heart (“DUM-heart”). Its peripheral projections revealed by axon tracing appeared as a meshwork of varicose endings encapsulating the heart. NOS-like immunoreactive profiles were found in the heart nerve. NO donors caused a dose-dependent increase in heart rate. This cardio-excitatory effect was negatively correlated to resting heart rate and seemed to be dependent on the physiological state of the animal. Hence, NO released from neurones such as the rhythmically active DUM-heart might exert continuous control over the heart. Possible mechanisms for the actions of NO on the heart and interactions with other neuromodulators co-localized in the DUM-heart neurone (octopamine, taurine, RF-amide-like peptide) are discussed.P.A.S. is the leading author, following the tragic death of Alexander Bullerjahn on 20.12.03.This work was supported by the Deutsche Forschungsgemeinschaft (grant number SFB 515; project of H.-J.P.). 相似文献
93.
Tomas G. A. Money Correne A. DeCarlo R. Meldrum Robertson 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2006,192(9):915-925
Activity in neural circuits can be modified through experience-dependent mechanisms. The effects of high temperature on a locust visual interneuron (the descending contralateral movement detector, DCMD) have previously been shown to be mitigated by prior exposure to sub-lethal, elevated temperatures (heat shock, HS). Activity in the DCMD is reduced at high temperature in naïve animals (control), whereas HS animals show a maintained spike count at all temperatures. We examined whether this finding was due to direct effects of temperature on visual processing, or whether other indirect feedback mechanisms were responsible for the observed effect in the DCMD. Activity in the DCMD was elicited using a computer-generated looming image, and the response was recorded extracellularly. The temperature of visual processing circuits contributes directly to HS-induced plasticity in the DCMD, as maintaining the brain at 25°C during a thoracic temperature ramp eliminated the high frequency activity associated with HS. Removing ascending input by severing the thoracic nerve cord reduced DCMD thermosensitivity, indicating that indirect feedback mechanisms are also involved in controlling the DCMD response to increased thoracic temperature. Understanding how thermosensitive feedback within the locust affects DCMD function provides insight into critical regulatory mechanisms underlying visually-guided behaviors. 相似文献
94.
Bräunig P 《Cell and tissue research》2008,333(1):159-168
The number and location of neurons, in the central nervous system, that project into the frontal connective was studied in
the locust by using retrograde neurobiotin staining. Staining one frontal connective revealed some 70 neurons in the brain.
Most of these were located within both tritocerebral lobes. Additional groups of neurons were located within the deutocerebrum
and protocerebrum. Some 60 neurons were labelled in the suboesophageal ganglion. These formed nine discernable populations.
In addition, two neurons were located in the prothoracic ganglion and two neurons in the first abdominal neuromere of the
metathoracic ganglion. Thus, some 250 neurons located within the head ganglia, and even neurons in thoracic ganglia, project
into the ganglia of the enteric nervous system. This indicates that the coordination between the central and enteric ganglia
is much more complex than previously thought. With the exception of some previously described dorsal unpaired median neurons
and a few motor neurons in the head ganglia, the identity and function of most of these neurons is as yet unknown. Possible
functions of the neurons in the thoracic ganglia are discussed. 相似文献
95.
Bacillus thuringiensis (Bt) has played an important role in biocontrol of pests. However, insecticidal activity of B. thuringiensis against locusts has been rarely reported. Bt strain BTH-13 exhibiting specific activity to locusts was isolated from a soil sample in China and characterized. Its bipyramidal parasporal crystal is mainly composed of a protein of 129 kDa, and produces a mature toxin of 64 kDa after activation. The pattern of total DNA from BTH-13 showed a large and three small plasmid bands. Known δ-endotoxin genes, cry1Aa, cry1Ab, cry1Ac, cry1C, cry3, cry4 and cry7Aa were not found from strain BTH-13 by PCR amplification. The sequence analysis of a DNA fragment produced by PCR amplification with degenerate cry-selective primers revealed that the fragment encoded a δ-endotoxin segment, which exhibited some similarity to several Cry proteins (41% of the highest similarity to Cry7Ba1). Toxicity tests were performed against Locusta migratoria manilensis, and the results demonstrated that trypsin-treated sporulated cultures and crystal proteins had high toxicity to larval and adult locusts. Cry toxin of BTH-13 was detected on the midguts of treated locusts using immunofluorescent technology, which confirmed the site of action of the crystal proteins in their toxicity for locusts. 相似文献
96.
Summary Two antidiuretic hormones are present in the corpora cardiaca of the locust, Locusta migratoria. They are located in the nervous and the glandular parts (NCC and GCC) respectively. A procedure was developed to avoid contamination of GCC by NCC. The peptide nature of the GCC hormone was established and its structural stability was studied. Additional evidence regarding the role of cyclic AMP as second messenger of the GCC antidiuretic factor was presented. 相似文献
97.
A technique is described for rearing germ-free desert locusts. Axenic insects appeared to develop and reproduce normally, therefore it is concluded that the gut bacterial flora does not contribute significantly to locust nutrition. However, it is suggested that the gut flora may benefit its host by contributing to the locust's defences against attack by pathogenic microorganisms. The results of morphometric measurements are discussed in terms of the bacterial origin of the so called phase pheromone, locustol. No evidence was found to support the hypothesis that microbial activity restricts gut carbohydrase. 相似文献
98.
G.S. Boyan 《Journal of insect physiology》1985,31(2):99-107
An identified interneurone (SA3) of the suboesophageal ganglion has an axon in both circumoesophageal connectives ascending to the brain. This is a novel morphology for a cell in the auditory system of the locust. The neurone is also novel for its physiological responses to sound in that it displays side-dependent response decrement (habituation). Responses to a tone directed at one ear decrement without affecting responses from the other ear. The responses on the decremented side recover when the opposite ear is stimulated. The decrement is the result of a diminishing amplitude of the compound excitatory post-synaptic potential but no inhibition is seen. Response decrement does not occur if the stimulus frequency is varied. 相似文献
99.
Gilles N Krimm I Bouet F Froy O Gurevitz M Lancelin JM Gordon D 《Journal of neurochemistry》2000,75(4):1735-1745
The alpha-like toxin from the venom of the scorpion Leiurus quinquestriatus hebraeus (Lqh III) binds with high affinity to receptor site 3 on insect sodium channels but does not bind to rat brain synaptosomes. The binding affinity of Lqh III to cockroach neuronal membranes was fivefold higher at pH 6.5 than at pH 7.5. This correlated with an increase in the electropositive charge on the toxin surface resulting from protonation of its four histidines. Radioiodination of Tyr(14) of Lqh III abolished its binding to locust but not cockroach sodium channels, whereas the noniodinated toxin bound equally well to both neuronal preparations. Radioiodination of Tyr(10) or Tyr(21) of the structurally similar alpha-toxin from L. quinquestriatus hebraeus (LqhalphaIT), as well as their substitution by phenylalanine, had only minor effects on binding to cockroach neuronal membranes. However, substitution of Tyr(21), but not Tyr(14), by leucine decreased the binding affinity of LqhalphaIT approximately 87-fold. Thus, Tyr(14) is involved in the bioactivity of Lqh III to locust receptor site 3 and is not crucial for the binding of LqhalphaIT to this site. In turn, the aromatic ring of Tyr(21) takes part in the bioactivity of LqhalphaIT to insects. These results highlight subtle architectural variations between locust and cockroach receptor site 3, in addition to previous results demonstrating the competence of Lqh III to differentiate between insect and mammalian sodium channel subtypes. 相似文献
100.
Summary At the end of blastokinesis, serosal epitheliae of 4- to 5-day-old embryos of Locusta migratoria contain an immunohistologically detectable cytosolic protein (Mr 240 kDa) which is related to the juvenile hormone carrier-protein in the haemolymph of the same species and which binds tritiated juvenile hormone 3 (JH3) (Kd10–8 M). At this early stage of development the corpora allata of the embryo are not yet fully differentiated and do not synthesize JH3 in organ cultures. The earliest detectable JH3 production by corpora allata in isolated heads is on day 6. On the other hand, serosal epitheliae of 4- to 5-day-old embryos produce JH3 in organ cultures, as has been shown by methylation of (10-3H)-JH3-acid to (10-3H)-JH3, and by incorporation of tritiated CH3 from l-(methyl-3H)-methionine into JH3. Isolated heads and abdomens of the embryos used as donors for the serosal preparations did not show methyl transferase activity responsible for JH3 biosynthesis. The serosal cells represent a hitherto unrecognized source of methyl transferase activity and of JH3 production. Degradation of JH3 to JH3-acid was also observed.Dedicated to Professor Herbert Röller on the occasion of his 60th birthday 相似文献