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181.
The endoplasmic reticulum (ER) molecular chaperone, BiP, plays a role in the cotranslational translocation and subsequent
folding and assembly of newly synthesized proteins targeted to the ER and secretory pathway. The sequence encoding a Douglas-fir
(Pseudotsuga menziesii [Mirb] Franco) BiP homologue (PmBiP) was identified by differential screening of a seedling cDNA library. Southern blotting
indicated that PmBiP is most likely present as a single copy. The deduced amino acid sequence of PmBiP contains an HEEL tetrapeptide
sequence which functions to retain PmBiP in the ER and is different from HDEL commonly found in angiosperm plant BiPs. Amino
acid sequence alignment and phylogenetic analysis show that PmBiP is highly similar to other plant BiPs yet forms a distinct
phylogenetic subgroup which is separate from the angiosperm BiPs. Northern and western blotting revealed that PmBiP is subject
to developmental regulation during seed development, germination, and early seedling growth and is seasonally regulated in
needles of young seedlings.
Received: 21 February 2000 / Accepted: 13 April 2000 相似文献
182.
Gravity independence of seed-to-seed cycling in Brassica rapa 总被引:2,自引:0,他引:2
Musgrave ME Kuang A Xiao Y Stout SC Bingham GE Briarty LG Levenskikh MA Sychev VN Podolski IG 《Planta》2000,210(3):400-406
Growth of higher plants in the microgravity environment of orbital platforms has been problematic. Plants typically developed
more slowly in space and often failed at the reproductive phase. Short-duration experiments on the Space Shuttle showed that
early stages in the reproductive process could occur normally in microgravity, so we sought a long-duration opportunity to
test gravity's role throughout the complete life cycle. During a 122-d opportunity on the Mir space station, full life cycles
were completed in microgravity with Brassica rapa L. in a series of three experiments in the Svet greenhouse. Plant material was preserved in space by chemical fixation, freezing,
and drying, and then compared to material preserved in the same way during a high-fidelity ground control. At sampling times
13 d after planting, plants on Mir were the same size and had the same number of flower buds as ground control plants. Following
hand-pollination of the flowers by the astronaut, siliques formed. In microgravity, siliques ripened basipetally and contained
smaller seeds with less than 20% of the cotyledon cells found in the seeds harvested from the ground control. Cytochemical
localization of storage reserves in the mature embryos showed that starch was retained in the spaceflight material, whereas
protein and lipid were the primary storage reserves in the ground control seeds. While these successful seed-to-seed cycles
show that gravity is not absolutely required for any step in the plant life cycle, seed quality in Brassica is compromised by development in microgravity.
Received: 3 August 1999 / Accepted: 27 August 1999 相似文献
183.
The gibberellin (GA) economy of young pea (Pisum sativum L.) fruits was investigated using a range of mutants with altered GA biosynthesis or deactivation. The synthesis mutation
lh-2 substantially reduced the content of both GA4 and GA1 in young seeds. Among the other synthesis mutations, ls-1, le-1 and le-3, the largest reduction in seed GA1 content was only 1.7-fold (le-1), while GA4 was not reduced in these mutants, and in fact accumulated in some experiments (compared with the wild type). Mutation sln appeared to block the step GA20 to GA29 in young pods and seeds, but not as strongly as in older seeds. Mutations ls-1, le-1 and le-3 markedly reduced pod GA1 levels, but pod elongation was not affected. After feeds of [13C,3H]GA20 to leaves, the pods contained 13C,3H-labelled GA20, GA1, GA29 and GA81, and the seeds, [13C,3H]GA20 and [13C,3H]GA29. These findings are discussed in relation to recent suggestions regarding the role and origin of GA1 in pea fruits.
Received: 6 June 1997 / Accepted: 15 July 1997 相似文献
184.
轮钟花属的恢复及其花粉和种皮证据 总被引:4,自引:0,他引:4
光学显微镜和扫描电镜观察表明,金钱豹属(广义)花粉明显分为两个类型:Campanumoea inflata和C.javanica subsp.laponica的花粉5~8沟,外壁具相对密的短刺,刺高不过1μm,而C.lancifolia,C.celebica和C.parviflora的花粉3孔沟,外壁刺稀疏,高于2μm。种子表面纹饰也同样可分为 两类,前两个种一类,其种子表面网状,网眼规则而多角形,直径大于网脊宽度,网脊上的次级纹饰为念 珠状,而后三种为一类,其种子表面网眼不规则,直径与网脊宽度近相等,网脊上的次级纹饰绳索状。可 见花粉特征与种皮性状是高度相关的。后三个种所属的分类群就是被归并了的属Cyclocodon Griffith。 综合花粉、种皮及外部形态,这个属应予恢复。其近缘属应是Platycodon,而不是Campanumoea。 相似文献
185.
J. A. Wilmer S. R. Abrams J. P. F. G. Helsper L. H. W. van der Plas 《Journal of Plant Growth Regulation》1998,17(1):19-23
Modification of the structure of abscisic acid (ABA) has been reported to result in modification of its physiologic activity.
In this study we tested the effect of removing methyl groups from the ring and of chirality of ABA on activity in microspore-derived
embryos of oilseed rape (Brassica napus L.). The natural (+)-ABA molecule induced growth inhibition and an increase in the amount of erucic acid accumulated in the
oil at medium concentrations less than 1 μm. (−)-ABA showed similar effects. Removing the 7′-methyl group resulted in a dramatic decrease in activity: (+)-7′-demethyl-ABA
retained some activity as a growth inhibitor; a 10–100 μm concentration of this compound was needed for a response, and (−)-7′-demethyl-ABA was almost completely inactive. Similar
effects were observed with regard to elongase activity, which catalyzes erucic acid biosynthesis from oleic acid. Removal
of the 8′- and 9′-methyl groups resulted in a more complex response. These compounds all showed intermediate activity; for
growth inhibition, the presence of the 9′-methyl was the more important determinant, whereas chirality dominated the response
on erucic acid accumulation, with the (+)-enantiomers being more active.
Received July 25, 1997; accepted October 31, 1997 相似文献
186.
In order to assess the mechanisms through which the spatial structure of the population influences female reproductive success,
spatial distribution of clones, degrees of limitation of legitimate (inter-morph) pollination, type and abundance of pollen
loaded on the stigmas, and seed set were measured for many clones of two natural populations of the distylous clonal plant,Persicaria japonica. Within the populations, according to the spatial relation to the nearest opposite morph clone, individual clones were assorted
into two spatial types,i.e., clones that congregated with clones of the opposite morph (congregating clones), and clones that occurred singly at a considerable
distance from the nearest opposite-morph clone (single clones). The pollination success,i.e., the proportion of legitimately pollinated flowers, and seed set were severely limited in the single clones compared to the
congregating clones. Since artificial legitimate pollination improved the seed set in single clones, at least to some degree
pollination failure was responsible for the reduced seed set in the single clones. 相似文献
187.
We conducted an experiment in a natural population of Alstroemeria
aurea, a clonal perennial, to determine (1) if reproduction was resource limited, and (2) if fruits would be selectively filled
based on differences in pollination intensity when pollen loads were adequate for full seed set. Under these conditions, differences
in pollination intensity are unlikely to affect seed number, but could affect seed quality, providing an interesting test
of the gametophytic competition hypothesis. To test for resource limitation, percent fruit maturation, number of seeds per
fruit and average seed weight were compared to paired controls for ramets in which all but one fruit was removed. To test
the effect of pollination intensity on selective resource allocation, three types of pollination treatments were performed:
(1) all flowers of the single inflorescence received a low pollen load, (2) all flowers received a high pollen load, (3) alternate
flowers of the inflorescence received either a high or a low pollen load. We determined the percentage of fruit that reached
maturity, counted the number of seeds and ovules and calculated the average seed weight for all capsules in each treatment.
Resources appeared to limit reproduction in this population since seed number and weight were significantly higher than in
controls when competing capsules were removed. At the whole ramet level, a four fold difference in pollen loads had no significant
effect on any of the parameters measured. However, when pollination intensity varied within an inflorescence, the number of
seeds per fruit increased by about 10% in flowers that received the higher pollen load. We observed the same trend in each
of 2 years, but the increase was significant in only 1 year. The differences, although not great, were only slightly smaller
than when all competing fruits were removed, and were consistent with selective resource allocation based on pollination intensity
independent of seed set.
Received: 28 September 1997 / Accepted: 30 April 1998 相似文献
189.
Abstract. This paper deals with the spatial distribution pattern of the bird-dispersed plant Daphne gnidium in a 10-yr abandoned field under Mediterranean conditions. Colonization of Mediterranean old-fields by bird-dispersed plants is expected to fit a theoretical model in which (1) seed dispersal follows a negative exponential curve with the distance from the seed source and (2) seedlings are better established under perches (nucleation sensu Yarranton & Morrison 1974). However, post-dispersal processes such as seed predation, seed germination and seedling establishment are also spatial-dependent and can lead to spatial autocorrelation in the seedling distribution within an old-field. Results show that both processes in the model (curve of seed dispersal and nucleation) significantly explained the spatial distribution of the seedlings, but some spatial variance remained unexplained. The semivariogram with the statistical residuals of the model detected spatial dependence at small (< 20 m) and large (> 250 m) distance intervals, indicating that some mechanisms with spatial components, apart from the curve of seed dispersal and nucleation under perches, also determined the distribution of seedlings colonizing fields. At scales below 20-m intervals, semivariance increased indicating that similarity between plots is lost when distance increases between them. This pattern may be explained because the favourable micro-environmental conditions for establishment produced under perches could be extended towards neighbour plots where perches were absent. A flat semi-variogram between 20-m and 250-m intervals shows spatial independence along this range. From 250 m on, the semivariance increased again, indicating spatial dependence at coarse-scale. It is possible that the colonization model failed at this scale because different spatial processes to those included in the model (perch presence and distance to the shrubland) could be controlling seed colonization at coarse-scale. 相似文献
190.
R.M. Cowling,D.M. Richardson & S.M. Pierce (eds.) 1977. Vegetation of Southern Africa. 总被引:4,自引:0,他引:4
We determined the role of bird dispersal in seed and seedling dynamics of the tree Kalopanax pictus from 7 years of observing seed rain and seedling emergence in a broad-leaved deciduous forest in central Japan. We also performed an experiment on the influence of seed pulp on germination of seeds of K. pictus. Seeds of this species can lie dormant for several years, and this causes rather constant yearly seedling emergence in spite of irregular seed production. The spatial distribution of the seedlings that emerged each year (maximum distance from nearest conspecific seed-bearing tree of 90 m) was wider than that of gravity-dispersed seeds (max. distance of 37 m), suggesting seed dispersal by birds in winter. Emerged seedling densities at sites over 20 m from the nearest conspecific seed-bearing tree were highest in the spring of 1991, about half a year after the largest seed fall of the observation period. However, emerged seedling densities within 20 m from seed-bearing trees were highest in 1992, 1.5 years after the largest seed fall. These field observations may be explained by the experimental results on the effects of seed pulp on germination. Intact seeds germinate slowly at low germination rates, while seeds without seed pulp germinate quickly at high germination rates. Fallen seeds with seed pulp thus appear to form a seed bank near seed sources (temporal dispersal), while seeds scattered by birds appear to increase the possibility of reaching the present safe sites in distant areas with quick germination (spatial dispersal). 相似文献