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Effects of growth light intensity on the temperature dependence of CO2 assimilation rate were studied in tobacco (Nicotiana tabacum) because growth light intensity alters nitrogen allocation between photosynthetic components. Leaf nitrogen, ribulose 1·5‐bisphosphate carboxylase/oxygenase (Rubisco) and cytochrome f (cyt f) contents increased with increasing growth light intensity, but the cyt f/Rubisco ratio was unaltered. Mesophyll conductance to CO2 diffusion (gm) measured with carbon isotope discrimination increased with growth light intensity but not with measuring light intensity. The responses of CO2 assimilation rate to chloroplast CO2 concentration (Cc) at different light intensities and temperatures were used to estimate the maximum carboxylation rate of Rubisco (Vcmax) and the chloroplast electron transport rate (J). Maximum electron transport rates were linearly related to cyt f content at any given temperature (e.g. 115 and 179 µmol electrons mol?1 cyt f s?1 at 25 and 40 °C, respectively). The chloroplast CO2 concentration (Ctrans) at which the transition from RuBP carboxylation to RuBP regeneration limitation occurred increased with leaf temperature and was independent of growth light intensity, consistent with the constant ratio of cyt f/Rubisco. In tobacco, CO2 assimilation rate at 380 µmol mol?1 CO2 concentration and high light was limited by RuBP carboxylation above 32 °C and by RuBP regeneration below 32 °C.  相似文献   
3.
1. The egg size of insects can vary depending on maternal body size or resource status, and it may influence offspring body size by determining initial resource level. 2. The giant rhinoceros beetle Trypoxylus dichotomus exhibits considerable variation in body size, some of which is attributed to the variation in larval food (humus) quality, although a substantial amount of variation in body size remains unexplained. In the present study, changes in the egg size and offspring body size in response to several maternal variables were examined (i.e. body size, age, and, nutritional status). 3. Nutritional intake of the females during the adult stage did not affect the egg size. Larvae hatched from small eggs partially recovered from the initial disadvantage during their ontogenetic processes by increasing growth rate (i.e. compensatory growth); however, there was still a positive relationship between egg size and pupal body size. 4. Older females produced small eggs, but because of compensatory growth, the pupae were no longer small. By contrast, due to a lack of compensatory growth, small females produced small eggs as well as small pupae. 5. These results suggest that maternal body size affects offspring body size through effects on egg size. This transgenerational effect may account for some of the variation in adult body size of T. dichotomus.  相似文献   
4.
1. Farming by non‐human organisms has arisen independently in several animal lineages, allowing them to survive on food sources that are otherwise difficult to access. However, agricultural gardens are prone to invasion by parasites that overgrow cultivars in the absence of host animals. The presence of garden parasites and associated host adaptations are well studied in advanced fungal agriculture practised by social insects (ants, termites, and ambrosia beetles), but the impact of garden parasites in more primitive forms of agriculture is poorly known. The aim of the present study was to report the presence of weed fungi in fungal gardens of the non‐social lizard beetle Doubledaya bucculenta Lewis (Coleoptera: Erotylidae: Languriinae), which cultivates the yeast Wickerhamomyces anomalus (E.C. Hansen) Kurtzman, Robnett & Bas.‐Powers in the internodes of recently dead bamboo culms. 2. The filamentous fungi Arthrinium spp., Fusarium spp., and an unidentified species were isolated from the inner wall and insect‐made wall debris of bamboo internodes inhabited by the beetle. 3. When cultured together with the yeast in the absence of host larvae, Arthrinium sp.1 outcompeted the yeast, suggesting that this filamentous fungus can invade yeast gardens but is normally suppressed under natural conditions. 4. Rearing experiments showed that beetle larvae grew faster when grown on yeast cultures than when fed only Arthrinium sp.1. 5. These results suggest that Arthrinium sp.1 acts as a weed in the fungal gardens of D. bucculenta, inhibiting both growth of the beetle larvae and proliferation of the beneficial yeast.  相似文献   
5.
Abstract The Indian meal moth Plodia interpunctella Hübner (Lepidoptera: Pyralidae) diapauses as a last‐instar (fifth) larva. At 30 °C, no larvae enter diapause under any photoperiodic conditions; at 25 °C, the photoperiodic response curve is a long‐day type with a critical length of approximately 13 h light; at 20 °C, diapause is induced moderately even under long days (> 13 h). Cumulative effects of short days or long days on diapause induction are determined by alternate, stepwise and gradually changing regimes of photoperiod at 25 °C. When the larvae are repeatedly exposed to LD 16 : 8 h and LD 12 : 12 h photoperiods every other day, the incidence of diapause is 37%. When the larvae are placed under an LD 16 : 8 h photoperiod for 2 days and then under an LD 12 : 12 h photoperiod for 1 day, it is 38 %. Exposure to an LD 16 : 8 h photoperiod for 1 day and then to an LD 12 : 12 h photoperiod for 2 days induces only 15% diapause. This may indicate that the photoperiodic information is not accumulated in a simple fashion despite the generally accepted hypothesis (i.e. photoperiodic counter). Larvae exposed to an LD 16 : 8 h photoperiod for 5 days after oviposition express a very high incidence of diapause even under short days between an LD 2 : 22 h and LD 12 : 12 h photoperiod. After 10 days exposure to an LD 16 : 8 h photoperiod, however, the short day does not induce diapause strongly. On the other hand, an LD 12 : 12 h photoperiod in the early larval life is highly effective in the induction of diapause. A gradual increase or decrease of photoperiod (2 min day?1) shows that the direction of photoperiodic change does not affect the diapause determination.  相似文献   
6.
Spinach (Spinacia oleracea) plants were grown under the day/night temperature regime of 15/10 °C (LT) or 30/25 °C (HT). The plants were also transferred from HT to LT when the sample leaves were at particular developmental stages (HL-transfer). With fully mature leaves, the light-saturated photosynthetic rate (A) at the ambient CO2 concentration (Ca) of 1500 µL L−1 (A1500) and the initial slope of A versus intercellular CO2 concentration (Ci) at low Ci region (IS) were obtained to assess capacities of RuBP regeneration and carboxylation. Photosynthetic components including Rubisco and cytochrome f (Cyt f) were also determined. The optimum temperatures for A at Ca of 360 µL L−1 (A360), A1500 and IS in HT leaves were 27, 36 and 24 °C, whereas those in LT leaves were 18, 30 and 18 °C. The optimum temperatures in HL-transfer leaves approached those of LT leaves with the increase in the duration at LT. The shift in the optimum temperature was greater and quicker for IS than A1500. By the HL-transfer, the maximum values of A1500 and IS also increased. The maximum A1500 and Cyt f content increased more promptly than IS and Rubisco content. Changes in the Cyt f/Rubisco ratio were reflected to those in the A1500/IS ratio. Taken together, photosynthetic acclimation to low temperature in spinach leaves was due not only to the change in the balance of the absolute rates of RuBP regeneration and carboxylation but also to the large change in the optimum temperature of RuBP carboxylation.  相似文献   
7.
We investigated the hybrid origin of × Crepidiastrixeris denticulato-platyphylla using RAPDs and ITS sequence data. The putative parents Paraixeris denticulata and Crepidiastrum platyphyllum represent separate species, irrespective of geographical origin. The occurrence of species specific RAPD markers from P. denticulata and C. platyphyllum in × C. denticulato-platyphylla established unambiguously a hybrid origin between the two taxa. This was in line with the occurrence of a combination of morphological characters such as plant habit and floret numbers. The parent taxa differed from each other by 7 nucleotide substitutions and 2 indel events in the ITS region. The hybrids showed sequence additivity and most likely represent F1 plants, with the exception of two plants which were of possible F2 origin, possessing either the ITS sequences of one parent only, or one predominant ITS type. The hybrids occurred in two out of three localities where the parents occurred sympatrically. This fact, together with the short life-span of the plants, suggests that × C. denticulato-platyphylla exists as a result of repeated, frequent hybridization between the parent species.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 151 , 333–343.  相似文献   
8.
We investigated the sequence variation in the mitochondrial cytochrome c oxidase subunit 1 (mtCOI) gene and the nuclear ribosomal internal transcribed spacers (ncITS) of the calanoid copepod Acanthodiaptomus pacificus in Japan. A. pacificus individuals were divided into three divergent mtCOI lineages (mt-A, -B and -C). mt-A was distributed in the northernmost part of Japan, from Hokkaido to the northern part of Honshu Island, whereas mt-C was the southernmost lineage, distributed from central Honshu to Shikoku and Kyushu Islands. mt-B was distributed between these former two lineages, resulting in parapatry with mt-C and mt-A. In all lineages, 80% of the localities were fixed for a single haplotype, and different localities tended to have different haplotypes. The degree of genetic differentiation among these lineages (15–22%) was at an interspecific level, according to the criteria of the DNA barcode technique. However, the topology of ncITS was not congruent with that of mtCOI, as the reciprocal monophyly was not observed within mt-B and mt-C. Therefore, we merged them into the Southern Lineage and separated it from the Northern Lineage (i.e. mt-A). Evidence of introgression was found within the Southern Lineage, while gene flow was not observed between the Northern and Southern Lineages, suggesting that A. pacificus is a cryptic species complex. We also argue that genetic differentiations of A. pacificus in Japan may reflect the history of separation, transgression and regression of the landmass during the formation of current Japanese Archipelago.  相似文献   
9.
The concentration of ions in plant cells and tissues is an essential factor in determining physiological function. In the present study, we established that concentration gradients of mobile ions exist in both xylem exudates and tissues within a barley (Hordeum vulgare) primary leaf. For K+ and NO3?, ion concentrations generally decreased from the leaf base to the tip in both xylem exudates and tissues. Ion gradients were also found for Pi and Cl? in the xylem. The hydathode strongly absorbed Pi and re‐translocated it to the rest of the plant, whereas Cl? was extruded. The ion concentration gradients developed early during leaf growth, increased as the tissue aged and remained under both high and low transpiration conditions. Measurement of the expression profiles of Pi, K+ and NO3? transporters along the longitudinal axis of the leaf revealed that some transporters are more expressed at the hydathode, but for most transporters, there was no significant variation along the leaf. The mechanisms by which longitudinal ion gradients develop in leaves and their physiological functions are discussed.  相似文献   
10.
The communications between oocytes and granulosa cells in the ovary of the chum salmon, Oncorhynchus keta , were examined in follicles in which the oocytes were at the stage of germinal vesicle migration. Microvilli were seen extending through the radial canals of the egg envelope and terminating in either the subfollicular space or at the surface of granulosa cells. Cytoplasmic processes extending from granulosa cells toward oocytes were also observed; most of the processes appeared to end in the radial canals, but some passed through the canals and terminated as bulbs in slight depressions or indentations of the oolemma. Various types of junctional structures that participated in intimate association between these cells were seen. The granulosa cells were found to be firmly fixed on the surface of the intrafollicular oocyte by means of desmosomes or desmosome-like junctions. It is speculated that intrafollicular oocytes communicate with surrounding granulosa cells directly through gap junctions and indirectly by endocytosis of material released from the granulosa cells.  相似文献   
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