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111.
A new reliable protocol for the induction of adventitious shoot formation and plant regeneration from apple callus has been
developed. High regeneration frequency was obtained with this method in four different genotypes (Jork9, M26, Gala and McIntosh)
and callus maintained regeneration ability for several months. The procedure consists of inducing vegetative shoot apices,
excised from in vitro shoots, for 20 days in darkness on an MS medium without glycine, supplied with 17.8 μM BA, 2.7 μM NAA
and 250 mg l−1 cefotaxime. The explants are then transferred to a fresh auxin-free medium and given light. Histological studies revealed
that all the regenerated shoots originated from callus. Regenerated shoots were multiplied, rooted and successfully established
in soil.
Received: 2 April 1999 / Revision received: 10 November 1999 / Accepted: 15 November 1999 相似文献
112.
113.
Summary
Asclepias speciosa Torr, has latex-containing cells known as nonarticulated laticifers. In stem sections of this species, we have analyzed the
cell walls of nonarticulated laticifers and surrounding cells with various stains, lectins, and monoclonal antibodies. These
analyses revealed that laticifer walls are rich in (1→4) β-D-glucans and pectin polymers. Immunolocalization of pectic epitopes
with the antihomogalacturonan antibodies JIM5 and JIM7 produced distinct labeling patterns. JIM7 labeled all cells including
laticifers, while JIM5 only labeled mature epidermal cells and xylem elements. Two antibodies, LM5 and LM6, which recognize
rhamnogalacturonan I epitopes distinctly labeled laticifer walls. LM6, which binds to a (l→5) α-arabinan epitope, labeled
laticifer walls more intensely than walls of other cells. LM5, which recognizes a (1→4) β-D-galac-tan epitope, did not label
laticifer segments at the shoot apex but labeled more mature portions of laticifers. Also the LM5 antibody did not label cells
at the shoot apical meristem, but as cells grew and matured the LM5 epitope was expressed in all cells. LM2, a monoclonal
antibody that binds to β-D-glucuronic acid residues in arabinogalactan proteins, did not label laticifers but specifically
labeled sieve tubes. Sieve tubes were also specifically labeled byRicinus communis agglutinin, a lectin that binds to terminal β-D-galactosyl residues. Taken together, the analyses conducted showed that laticifer
walls have distinctive cytochemical properties and that these properties change along the length of laticifers. In addition,
this study revealed differences in the expression of pectin and arabinogalactan protein epitopes during shoot development
or among different cell types. 相似文献
114.
Dynamic habitat suitability modelling reveals rapid poleward distribution shift in a mobile apex predator
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Nicholas J. Hill Andrew J. Tobin April E. Reside Julian G. Pepperell Tom C. L. Bridge 《Global Change Biology》2016,22(3):1086-1096
Many taxa are undergoing distribution shifts in response to anthropogenic climate change. However, detecting a climate signal in mobile species is difficult due to their wide‐ranging, patchy distributions, often driven by natural climate variability. For example, difficulties associated with assessing pelagic fish distributions have rendered fisheries management ill‐equipped to adapt to the challenges posed by climate change, leaving pelagic species and ecosystems vulnerable. Here, we demonstrate the value of citizen science data for modelling the dynamic habitat suitability of a mobile pelagic predator (black marlin, Istiompax indica) within the south‐west Pacific Ocean. The extensive spatial and temporal coverage of our occurrence data set (n = 18 717), collected at high resolution (~1.85 km2), enabled identification of suitable habitat at monthly time steps over a 16‐year period (1998–2013). We identified considerable monthly, seasonal and interannual variability in the extent and distribution of suitable habitat, predominately driven by chlorophyll a and sea surface height. Interannual variability correlated with El Nino Southern Oscillation (ENSO) events, with suitable habitat extending up to ~300 km further south during La Nina events. Despite the strong influence of ENSO, our model revealed a rapid poleward shift in the geometric mean of black marlin habitat, occurring at 88.2 km decade?1. By incorporating multiple environmental factors at monthly time steps, we were able to demonstrate a rapid distribution shift in a mobile pelagic species. Our findings suggest that the rapid velocity of climate change in the south‐west Pacific Ocean is likely affecting mobile pelagic species, indicating that they may be more vulnerable to climate change than previously thought. 相似文献
115.
The effect of changing climatic conditions on wild populations has been the subject of much recent research. Most attention has been on the direct effects of climate changes on species of lower trophic levels and on the negative consequences of climate change. However, a deeper understanding of how climate change affects apex predators is vital, as they are keystone species that have a disproportionate effect on ecosystems. Studying survival in an apex predator requires individual‐based data from long‐term studies and is complicated by the integration of climatic effects on lower trophic levels. Here we assess how climate affects the survival of the Common Buzzard Buteo buteo. We analysed the survival of 670 males and 669 females over the period 1989–2011, during which time our study population quadrupled. We used mark–recapture survival analysis of individual resightings of breeding adults to identify the environmental factors best explaining survival. A decrease in the North Atlantic Oscillation (NAO) index increased survival to an extent that largely explains the population increase. This might be caused by higher Common Vole Microtus arvalis survival in drier conditions and under snow cover. Buzzard survival appeared to increase more for males than for females, possibly due to the males' higher sensitivity to winter food availability resulting from their smaller body mass. However, we also found that the effect of NAO strongly depended on the area in which individuals lived, especially for females. This may have been caused by the recolonization of Eagle Owls Bubo bubo in some parts of our study area. This study suggests that climatic changes can have complex effects on species of higher trophic levels via an interaction with their prey. 相似文献
116.
Excised shoot apices of maize (Zea mays L.), comprising the apical meristem and one or two leaf primordia, have been cultured and can form rooted plantlets. The plantlets, derived from meristems that had previously formed 7–10 nodes, develop into mature, morphologically normal plants with as many nodes as seed-grown plants. These culture-derived plants exhibited the normal pattern of development, with regard to the progression of leaf lengths along the plant and position of axillary buds and aar shoots. Isolation of the meristem from previously formed nodes reinitiates the pattern and number of nodes formed in the new plant. Thus, cells of the meristem of a maize plant at the seedling stage are not determined to form a limited number of nodes. 相似文献
117.
《Current biology : CB》2021,31(22):4887-4897.e5
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118.
119.
Summary A recent review paper by Glen et al . in Austral Ecology (2007, Volume 32 , 492–501) canvassed anecdotal and scientific evidence relating to the role of the Dingo as regulator of ecosystem processes in Australian landscapes. Their review forms part of an increasing volume of literature about the ecological roles of top-order or apex predators around the globe. Although recognizing the possible functional significance of the Dingo is a noteworthy subject matter, the management of the species at an ecosystem scale is complicated by a range of practical and theoretical issues. Perhaps the most significant challenge is the degree to which the Dingo is hybridized with the domestic Dog gone wild (Feral Dog). We suggest here that there is a range of research questions that need to be experimentally addressed as a matter of urgency. This includes but is not limited to understanding the ecological significance of Dingo–Dog hybridization. Such research should precede other research initiatives suggested by Glen et al. such as reintroducing individuals of the pure Dingo back into landscapes. This is particularly the case for south-eastern mainland Australia where the incidence of Dingo–Dog hybridization is high and the ecological consequences of this poorly understood. Finally, new terminology may be needed relating to Dingo and/or Wild Dog management that more clearly reflects both the genetic status of the species as well as its ecological function. 相似文献
120.
Seeds of Silene coeli-rosa L. were germinated and grown at 20°C in short days of 8 h light from fluorescent and tungsten (F + T) bulbs and 16 h darkness for 28 days (day 0). At 1700 h of day 0, the plants were exposed to 16 h light from T (LD) followed by 8 h F + T, or the same treatment interrupted at 1700 h of day 0 by 20 or 60 min darkness. Plants were exposed to tritiated (methyl-[3 H])-thymidine for 2 h (1645–1845 h) and sampled every 2 h for 24 h. The cell cycle (percentage labelled mitoses method), and changes in cell number were measured in the shoot apical meristems. The cell cycle in the LD, 20 and 60 min dark-interrupted LD (diLD) treatments was 10, 11 and 13 h, respectively. Mean cell generation times were ca 3–5 h longer, suggesting that the shorter cell cycles were transient. The proportions of cells with 2C or 4C amounts of nuclear DNA, indicated that imposition of darkness resulted in a progressive lengthening of G1 from about 3 h in the LD to 7 h in the 60 min diLD treatment. Conversely, G2 shortened from about 4 h in the LD to 3 h in the 60 min diLD treatment. Measurements of labelling index indicated that S-phase was about 1.5 to 2 h in each treatment. The data are discussed in relation to the known inhibitory effect of the diLD treatments on flowering. 相似文献