Grain number and seed-setting rate are components of crop yield.Cytokinin influences grain yield.However,emerging studies suggest that high cytokinin signals often lead to reduced branching or seed-setting rate,leadin...Grain number and seed-setting rate are components of crop yield.Cytokinin influences grain yield.However,emerging studies suggest that high cytokinin signals often lead to reduced branching or seed-setting rate,leading to reduced grain yield,although the mechanisms remain unclear.In this study,we identified and characterized the rice(Oryza sativa L.)gene LONELY GUY-LIKE 8(LOGL8),based on analysis of the LOGL8-pm(promoter mutant of LOGL8)mutant,which harbors a T-DNA insertion in the promoter of this gene.The mutation in LOGL8-pm causes ectopic hyperexpression of LOGL8 in inflorescence organs,resulting in plants with smaller panicles and defective ovules lacking archesporial cells and integuments.Knockout of LOGL8 caused pollen abortion,leading to a reduced seed-setting rate.LOGL8 encodes a putative cytokinin-activating enzyme.Our results showed that LOGL8 directly catalyzes the biosynthesis of bioactive cytokinins.Therefore,we propose that the ectopic expression of LOGL8 disrupts cytokinin spatiotemporal distribution and causes inhibition of LONELY GUY(LOG),which affects panicle branching and female organ development.These findings reveal the important role of LOGL8 in male development,and highlight the delicate balance of local cytokinin levels during panicle branching and female organ development.展开更多
Pollen morphology and hydration, ovule development, formation of pollination drop and the pollination process of Taxus chinensis (Pilg.) Rehd were investigated in detail. The results showed that mature pollen was ...Pollen morphology and hydration, ovule development, formation of pollination drop and the pollination process of Taxus chinensis (Pilg.) Rehd were investigated in detail. The results showed that mature pollen was one_celled, irregular in shape, nonsaccate, and the surface was covered with orbicules. When pollen became hydrated, the intine swelled and the exine bursted. The exine usually remained on the surface of water or on the pollination drop all the time, while the rest portion of the pollen sank into the drop of water or the pollination drop. In the late August, the down_curved female buds could be observed in the field trees. The downturning of the female buds was an characteristic feature discriminating from the vegetative buds. At this stage ovular primordium was present in the female bud with a dome_shaped nucellar primordium encircled by a rudimentary integument. The integument grew fast and overgrew the nucellus. In the March of the following year, the ovule formed a micropylar canal about 1?000 μm in length, 200-300 μm in width. Except the micropyle, the other part of the ovule was enclosed by 20-25 scales. During the early stage of the ovule development, the nucellar surface clearly showed cell configuration; but a membrane_like structure covering the nucellar apex appeared in the late stage of the ovule development, and subsequently broke down with nucellar cell disintegration before pollen shedding. The disintegrated cell products might partake in the formation of the pollination drop. Before and during pollination, the nucellar cells contained abundant mitochondria, endospermic reticulum and dictysomes with vesicles; the plasma membrane was undulated and there was no accumulation of electron_dense substances in the pericytoplasm. Pollination drops usually occurred at night, and disappeared by noon in the field tree. 15 days before pollination, the in vitro ovules from the field trees already had the capability of producing pollination drops, which could last for 4-5 days indoors. However, after these drops received pollen, they did not withdraw noticeably compared with the unpollinated ones. The retraction of the pollination drop was presumed not to be a nonmetabolic outcome but rather a result of evaporation.展开更多
Salinity is a major abiotic stress affecting plant growth and productivity. Considerable genetic variation is present in rice in response to salt stress, with higher sensitivity during early seedling and reproductive ...Salinity is a major abiotic stress affecting plant growth and productivity. Considerable genetic variation is present in rice in response to salt stress, with higher sensitivity during early seedling and reproductive stage. In this study, physiological changes in leaves and developing panicles of rice genotypes (IR686, Sadri, Rc222, CSR28, IR670 and Pokkali) contrasting in salt tolerance at the reproductive stage were evaluated in greenhouse experiment under salt stress. The results showed that IR670 and the tolerant-check Pokkali maintained lower Na^+/K^+ ratio, less reduction in chlorophyll concentration, lower malondialdehyde (MDA) production, higher concentrations of reduced ascorbate (reduced AsA), higher proline accumulation and lower percentage reduction in pollen viability than the salt-sensitive genotypes under salt stress. The higher concentration of reduced AsA suggests an efficient ROS-scavenging system. Physiological measurements and pollen viability analysis revealed that Sadri (moderately tolerant at the seedling stage) is sensitive to salt stress at the flowering stage. The findings will be useful in breeding salt tolerant varieties at both seedling and reproductive stages by selecting appropriate genotypes and phenotypes.展开更多
In angiosperms, initiation of ovule enlargement represents the start of seed development, the molecular mechanism of which is not yet elucidated. It was previously reported that pollen tube contents, rather than doubl...In angiosperms, initiation of ovule enlargement represents the start of seed development, the molecular mechanism of which is not yet elucidated. It was previously reported that pollen tube contents, rather than double fertilization, can trigger ovule enlargement. However, it remains unclear whether the signal（s） to trigger the initiation of ovule enlargement are from the sperm cells or fromthe pollen tubes. Recently, we identified a mutant dropl- drop2-, which produces pollen tubes with no sperm cells. Taking advantage of this special genetic material, we conducted pollination assays, and found that the ovules pollinated with dropl- drop2- pollen could initiate the enlargement and exhibited significant enlarged sizes at 36h after pollination in comparison with those unpollinated ovules. However, the sizes of the ovules pollinated with drops- drop2- pollen are significantly smaller than those of the ovules pollinated with wildtype pollen. These results demonstrate that the pollen tube, rather than the sperm cells, release the signal to trigger the initiation of ovule enlargement, and that double fertilization is required for further enlargement of the seeds.展开更多
In order to investigate the indication of major pollen types to source plants, 39 surface pollen samples are collected from 39 plant communities. The results show that diversity of pollen assemblages presents in diffe...In order to investigate the indication of major pollen types to source plants, 39 surface pollen samples are collected from 39 plant communities. The results show that diversity of pollen assemblages presents in different commu-nities. Chenopodiaceae pollen percentages are highest in Kalidium communities and Ceratoides communities (higher than 45%, average is 63.4%), but high Ephedra pollen per-centages (higher than 3.3%, average is 16.5%)in Ceratoides communities make it distinguished from Kalidium communi-ties. Artemisia pollen percentages (more than 50%) are much higher than Chenopodiaceae (less than 35%) in Artemisia Communities. Nitraria pollen percentages (higher than 2%, average is 13.6%) are highest in Nitraria communities com-pared with those in other community patterns. Tamariceae pollen percentages (higher than 2%, average is 8.6%) are highest both in Tetraena and Reaumuria communities com-pared with those in other community patterns. But in Reau-muria communities, Artemisia pollen percentages are higher than Chenopodiaceae with some other pollen types such as Gramineae, Compositae, Leguminosae; on the contrary, in Tetraena communities, Artemisia pollen percentages are less than Chenopodiaceae with few other pollen types. Calli-gonum pollen only appears in Calligonum communities (higher than 2%,average is 5%). The results of cluster analysis (CLA) and detrended correspondence analysis (DCA) show that the pollen indication to source plants can be reflected by association indices (A), over-representation in-dices (O), under-representation indices (U), R-value, the av-erage pollen percentages where parent plants are absent (Xa) and the average pollen percentages where parent plants are present (Xp). Zygophyllum, Calligonum, Tetraena, Tribulus and Tamariceae can indicate source plants very well, owing to high A scores. Artemisia, Chenopodiaceae and Gramineae have high R-values, and Nitraria, Cruciferae and sedum have high O scores, so they are over-represented types, but the higher Xp and the lower Xa values make that these pollen types can also indicate source plants moderately. Allium, Leguminosae, Roseceae, Pedicularis and Compositae have low A scores (less than 0.5), high O and/or U scores, so they cannot indicate source plants clearly. Some other pollen types, such as Pinus, Picea, Betula, Quercus, Ulmus, Ephedra, Elaegnaceae, Ranunculaceae, Caryophyllaceae, Polygona-ceae, Saxifragaceae, only appear in pollen assemblages, so their indication cannot be decided. Just like the pollen per-centage ratios of Artemisia and Chenopodiaceae (A/C), the ratios of Ephedra and Artemisia (E/A), Nitraria and Ephedra (N/E) can also indicate the aridity of environment. In typical desert communities, A/C ratios are less than 0.5, E/A ratios are more than 0.1, and N/E ratios are less than 1. In steppe desert, A/C ratios are 0.5―2, E/A ratios are less than 0.1, and N/E ratios are more than 1.展开更多
Plant flowering and breeding characteristics are important for us to understand the reproduction of plant populations. In this paper, we studied the reproduction characteristics of Jatropha curcas in Yuanjiang County ...Plant flowering and breeding characteristics are important for us to understand the reproduction of plant populations. In this paper, we studied the reproduction characteristics of Jatropha curcas in Yuanjiang County （23°36＇1＇4, 101°00＇E）, Yunnan Province. The plant produces flowers in dichasial inflorescences. Normally, the flowers are unisexual, and male and female flowers are produced in the same inflorescence. Only a few male flowers are produced in an inflorescence, and fruits are produced only through pollination between different flowers from the same or different plants. By the treatments of emasculation, bagging and artificial pollination in this experiment, there were few but same fruit set ratios when the inflorescences were emasculated, bagged, or bagged with net, except artificial pollination treatments, which showed that Jatropha curcas could produce fruit through apomixis but not wind pollination. When the inflorescences were unbagged, unemasculated and with free pollination treatments, or bagged, emasculated and with artificial cross-pollination treatments, or unbagged, emasculated and with free pollination treatments, there were many fruits produced. It showed that Jatropha curcas shows outcrossing, is self-compatible, and demanding for pollinators. Normally, the male flowers open first and a few flowers bloom in one day in a raceme. These flowers last a long time in bloom. However, a large number of female flowers open from the third to the fifth day, with some female flowers opening first in a few raceme. This shows a tendency to promote xenogamy and minimize geitonogamy.展开更多
The Pedicularis species provides ideal materials to study floral evolution because of their substantial flower variation based on a narrow genetic basis, even though they are almost exclusively pollinated by bumblebee...The Pedicularis species provides ideal materials to study floral evolution because of their substantial flower variation based on a narrow genetic basis, even though they are almost exclusively pollinated by bumblebee. These traits allow us to detect the evolutionary trends of floral parameters without considering genetic background and the difference of pollination vectors. The pollen-ovule ratio is widely used to estimate the pattern of resource investment in two sexual functions in flowering plants. Forty species representing all of the corolla types in Pedicularls were used to study pollen-ovule ratio, gamete investment, and their correlations. Results show that pollen-ovule ratio does not differ among both different corolla types and taxonomic groups. It is therefore suggested that pollen-ovule ratio should be a parallel evolution. The correlations between pollen-ovule ratio and pollen size （-）, and ovule size （＋） can be successfully explained in terms of sex allocation theory. The biological significance of such relationships was also discussed. Additionally, we analyzed the pattern of resource investment into female gamete, which has been somewhat neglected, and found that plants have different patterns of gamete investment between the two sexual functions.展开更多
Fifty-six surface pollen samples from different vegetation zones in the Yili Basin,western Tianshan Mountains,Xinjiang were analyzed to examine the relationships between the surface pollen assemblages and the original...Fifty-six surface pollen samples from different vegetation zones in the Yili Basin,western Tianshan Mountains,Xinjiang were analyzed to examine the relationships between the surface pollen assemblages and the original vegetation.A pollen analysis and a vegetation investigation with a discriminant analysis show that the pollen assemblages greatly differ across disparate vegetation zones.Twelve pollen taxa can be used as significant types for vegetation reconstruction in the basin.These taxa were the most abundant in the surface pollen samples.Cupressaceae pollen percentages were greater than 1%in Cupressaceae shrubs.More than5%of Picea pollen indicates the growth of a Picea forest within 5 km.The subalpine meadow that is distributed widely in the basin is characterized by high content of Artemisia,Chenopodiaceae,Poaceae,Picea,Asteraceae,Taraxacum and Arenaria pollen types.The Artemisia-Chenopodiaceae-Poaceae-Cannabaceae pollen assemblages indicate the presence of montane steppe in the area.Artemisia and Chenopodiaceae pollen dominate the desert steppe and Populus forest.Artemisia pollen percentages were greater than 60%in the Artemisia desert,whereas Chenopodiaceae pollen percentages exceeded 65%in the Chenopodiaceae desert.The Artemisia/Chenopodiaceae(A/C)ratios reflect the vertical moisture changes in the Yili Basin.The mean A/C ratios were greater than 1.2 in the subalpine meadow and montane steppe that occupy the humid zone in the basin.These ratios were between1 and 1.2 in the Cupressaceae shrubs,desert steppe,Populus forest and floodplain meadow.The ratios were less than 0.5 in the Chenopodiaceae desert,which is an arid environment.展开更多
Nfbp6 was a floral homeotic gene isolated from tobacco. It showed high homology with other class C genes. Using in situ hybridization technique, the expression of Nfbp6 was investigated in various stages of flower dev...Nfbp6 was a floral homeotic gene isolated from tobacco. It showed high homology with other class C genes. Using in situ hybridization technique, the expression of Nfbp6 was investigated in various stages of flower development. The results showed that Nfbp6 was expressed at low level during the initiation period of stamen and carpel primordia. In the later stage of flower bud development, the transcription level of Nfbp6 gene increased especially during the formation of pollen and ovule. The Nfbp6 gene expression was also observed in the transmitting tissue of style, stomium and circular cell clusters of the anther.展开更多
基金supported by the National Natural Science Foundation of China(31991222,32030080,31271301)the Guangdong Basic and Applied Basic Research Founation(2020A1515110207)the China Postdoctoral Science Foundation(2020M682726)。
文摘Grain number and seed-setting rate are components of crop yield.Cytokinin influences grain yield.However,emerging studies suggest that high cytokinin signals often lead to reduced branching or seed-setting rate,leading to reduced grain yield,although the mechanisms remain unclear.In this study,we identified and characterized the rice(Oryza sativa L.)gene LONELY GUY-LIKE 8(LOGL8),based on analysis of the LOGL8-pm(promoter mutant of LOGL8)mutant,which harbors a T-DNA insertion in the promoter of this gene.The mutation in LOGL8-pm causes ectopic hyperexpression of LOGL8 in inflorescence organs,resulting in plants with smaller panicles and defective ovules lacking archesporial cells and integuments.Knockout of LOGL8 caused pollen abortion,leading to a reduced seed-setting rate.LOGL8 encodes a putative cytokinin-activating enzyme.Our results showed that LOGL8 directly catalyzes the biosynthesis of bioactive cytokinins.Therefore,we propose that the ectopic expression of LOGL8 disrupts cytokinin spatiotemporal distribution and causes inhibition of LONELY GUY(LOG),which affects panicle branching and female organ development.These findings reveal the important role of LOGL8 in male development,and highlight the delicate balance of local cytokinin levels during panicle branching and female organ development.
文摘Pollen morphology and hydration, ovule development, formation of pollination drop and the pollination process of Taxus chinensis (Pilg.) Rehd were investigated in detail. The results showed that mature pollen was one_celled, irregular in shape, nonsaccate, and the surface was covered with orbicules. When pollen became hydrated, the intine swelled and the exine bursted. The exine usually remained on the surface of water or on the pollination drop all the time, while the rest portion of the pollen sank into the drop of water or the pollination drop. In the late August, the down_curved female buds could be observed in the field trees. The downturning of the female buds was an characteristic feature discriminating from the vegetative buds. At this stage ovular primordium was present in the female bud with a dome_shaped nucellar primordium encircled by a rudimentary integument. The integument grew fast and overgrew the nucellus. In the March of the following year, the ovule formed a micropylar canal about 1?000 μm in length, 200-300 μm in width. Except the micropyle, the other part of the ovule was enclosed by 20-25 scales. During the early stage of the ovule development, the nucellar surface clearly showed cell configuration; but a membrane_like structure covering the nucellar apex appeared in the late stage of the ovule development, and subsequently broke down with nucellar cell disintegration before pollen shedding. The disintegrated cell products might partake in the formation of the pollination drop. Before and during pollination, the nucellar cells contained abundant mitochondria, endospermic reticulum and dictysomes with vesicles; the plasma membrane was undulated and there was no accumulation of electron_dense substances in the pericytoplasm. Pollination drops usually occurred at night, and disappeared by noon in the field tree. 15 days before pollination, the in vitro ovules from the field trees already had the capability of producing pollination drops, which could last for 4-5 days indoors. However, after these drops received pollen, they did not withdraw noticeably compared with the unpollinated ones. The retraction of the pollination drop was presumed not to be a nonmetabolic outcome but rather a result of evaporation.
基金the International Rice Research InstituteDOST-ASTHRDPUniversity of the Philippines Visayas for providing support
文摘Salinity is a major abiotic stress affecting plant growth and productivity. Considerable genetic variation is present in rice in response to salt stress, with higher sensitivity during early seedling and reproductive stage. In this study, physiological changes in leaves and developing panicles of rice genotypes (IR686, Sadri, Rc222, CSR28, IR670 and Pokkali) contrasting in salt tolerance at the reproductive stage were evaluated in greenhouse experiment under salt stress. The results showed that IR670 and the tolerant-check Pokkali maintained lower Na^+/K^+ ratio, less reduction in chlorophyll concentration, lower malondialdehyde (MDA) production, higher concentrations of reduced ascorbate (reduced AsA), higher proline accumulation and lower percentage reduction in pollen viability than the salt-sensitive genotypes under salt stress. The higher concentration of reduced AsA suggests an efficient ROS-scavenging system. Physiological measurements and pollen viability analysis revealed that Sadri (moderately tolerant at the seedling stage) is sensitive to salt stress at the flowering stage. The findings will be useful in breeding salt tolerant varieties at both seedling and reproductive stages by selecting appropriate genotypes and phenotypes.
基金supported by National Natural Science Foundation of China(31620103903)partially by the 111 projectsupported by the Peking-Tsinghua Joint Center for Life Sciences
文摘In angiosperms, initiation of ovule enlargement represents the start of seed development, the molecular mechanism of which is not yet elucidated. It was previously reported that pollen tube contents, rather than double fertilization, can trigger ovule enlargement. However, it remains unclear whether the signal（s） to trigger the initiation of ovule enlargement are from the sperm cells or fromthe pollen tubes. Recently, we identified a mutant dropl- drop2-, which produces pollen tubes with no sperm cells. Taking advantage of this special genetic material, we conducted pollination assays, and found that the ovules pollinated with dropl- drop2- pollen could initiate the enlargement and exhibited significant enlarged sizes at 36h after pollination in comparison with those unpollinated ovules. However, the sizes of the ovules pollinated with drops- drop2- pollen are significantly smaller than those of the ovules pollinated with wildtype pollen. These results demonstrate that the pollen tube, rather than the sperm cells, release the signal to trigger the initiation of ovule enlargement, and that double fertilization is required for further enlargement of the seeds.
基金This work was supported by the National Natural Science Foundation of China(Grant No.40171095)the National Natural Science Foundation of Hebei Province(Grant No.402615)+1 种基金the Special Foundation for Preliminary Research of Key Research Project,Science and Technology Ministry of China(Grant No.2003CCA01800)the National Natural Foundation for the Famous Young(Grant No.49920205).
文摘In order to investigate the indication of major pollen types to source plants, 39 surface pollen samples are collected from 39 plant communities. The results show that diversity of pollen assemblages presents in different commu-nities. Chenopodiaceae pollen percentages are highest in Kalidium communities and Ceratoides communities (higher than 45%, average is 63.4%), but high Ephedra pollen per-centages (higher than 3.3%, average is 16.5%)in Ceratoides communities make it distinguished from Kalidium communi-ties. Artemisia pollen percentages (more than 50%) are much higher than Chenopodiaceae (less than 35%) in Artemisia Communities. Nitraria pollen percentages (higher than 2%, average is 13.6%) are highest in Nitraria communities com-pared with those in other community patterns. Tamariceae pollen percentages (higher than 2%, average is 8.6%) are highest both in Tetraena and Reaumuria communities com-pared with those in other community patterns. But in Reau-muria communities, Artemisia pollen percentages are higher than Chenopodiaceae with some other pollen types such as Gramineae, Compositae, Leguminosae; on the contrary, in Tetraena communities, Artemisia pollen percentages are less than Chenopodiaceae with few other pollen types. Calli-gonum pollen only appears in Calligonum communities (higher than 2%,average is 5%). The results of cluster analysis (CLA) and detrended correspondence analysis (DCA) show that the pollen indication to source plants can be reflected by association indices (A), over-representation in-dices (O), under-representation indices (U), R-value, the av-erage pollen percentages where parent plants are absent (Xa) and the average pollen percentages where parent plants are present (Xp). Zygophyllum, Calligonum, Tetraena, Tribulus and Tamariceae can indicate source plants very well, owing to high A scores. Artemisia, Chenopodiaceae and Gramineae have high R-values, and Nitraria, Cruciferae and sedum have high O scores, so they are over-represented types, but the higher Xp and the lower Xa values make that these pollen types can also indicate source plants moderately. Allium, Leguminosae, Roseceae, Pedicularis and Compositae have low A scores (less than 0.5), high O and/or U scores, so they cannot indicate source plants clearly. Some other pollen types, such as Pinus, Picea, Betula, Quercus, Ulmus, Ephedra, Elaegnaceae, Ranunculaceae, Caryophyllaceae, Polygona-ceae, Saxifragaceae, only appear in pollen assemblages, so their indication cannot be decided. Just like the pollen per-centage ratios of Artemisia and Chenopodiaceae (A/C), the ratios of Ephedra and Artemisia (E/A), Nitraria and Ephedra (N/E) can also indicate the aridity of environment. In typical desert communities, A/C ratios are less than 0.5, E/A ratios are more than 0.1, and N/E ratios are less than 1. In steppe desert, A/C ratios are 0.5―2, E/A ratios are less than 0.1, and N/E ratios are more than 1.
文摘Plant flowering and breeding characteristics are important for us to understand the reproduction of plant populations. In this paper, we studied the reproduction characteristics of Jatropha curcas in Yuanjiang County （23°36＇1＇4, 101°00＇E）, Yunnan Province. The plant produces flowers in dichasial inflorescences. Normally, the flowers are unisexual, and male and female flowers are produced in the same inflorescence. Only a few male flowers are produced in an inflorescence, and fruits are produced only through pollination between different flowers from the same or different plants. By the treatments of emasculation, bagging and artificial pollination in this experiment, there were few but same fruit set ratios when the inflorescences were emasculated, bagged, or bagged with net, except artificial pollination treatments, which showed that Jatropha curcas could produce fruit through apomixis but not wind pollination. When the inflorescences were unbagged, unemasculated and with free pollination treatments, or bagged, emasculated and with artificial cross-pollination treatments, or unbagged, emasculated and with free pollination treatments, there were many fruits produced. It showed that Jatropha curcas shows outcrossing, is self-compatible, and demanding for pollinators. Normally, the male flowers open first and a few flowers bloom in one day in a raceme. These flowers last a long time in bloom. However, a large number of female flowers open from the third to the fifth day, with some female flowers opening first in a few raceme. This shows a tendency to promote xenogamy and minimize geitonogamy.
基金Supported by the National Natural Science Foundation of China （30500032） and the State Key Basic Research and Development Plan of China （2000046804）.
文摘The Pedicularis species provides ideal materials to study floral evolution because of their substantial flower variation based on a narrow genetic basis, even though they are almost exclusively pollinated by bumblebee. These traits allow us to detect the evolutionary trends of floral parameters without considering genetic background and the difference of pollination vectors. The pollen-ovule ratio is widely used to estimate the pattern of resource investment in two sexual functions in flowering plants. Forty species representing all of the corolla types in Pedicularls were used to study pollen-ovule ratio, gamete investment, and their correlations. Results show that pollen-ovule ratio does not differ among both different corolla types and taxonomic groups. It is therefore suggested that pollen-ovule ratio should be a parallel evolution. The correlations between pollen-ovule ratio and pollen size （-）, and ovule size （＋） can be successfully explained in terms of sex allocation theory. The biological significance of such relationships was also discussed. Additionally, we analyzed the pattern of resource investment into female gamete, which has been somewhat neglected, and found that plants have different patterns of gamete investment between the two sexual functions.
基金supported by the National Natural Science Foundation of China(41102113 and 41172161)the National Basic Research Program of China (2010CB950204)a MOST Special Fund (KN212431) from the Institute of Vertebrate Paleontology and Paleoanthropology for supporting the project
文摘Fifty-six surface pollen samples from different vegetation zones in the Yili Basin,western Tianshan Mountains,Xinjiang were analyzed to examine the relationships between the surface pollen assemblages and the original vegetation.A pollen analysis and a vegetation investigation with a discriminant analysis show that the pollen assemblages greatly differ across disparate vegetation zones.Twelve pollen taxa can be used as significant types for vegetation reconstruction in the basin.These taxa were the most abundant in the surface pollen samples.Cupressaceae pollen percentages were greater than 1%in Cupressaceae shrubs.More than5%of Picea pollen indicates the growth of a Picea forest within 5 km.The subalpine meadow that is distributed widely in the basin is characterized by high content of Artemisia,Chenopodiaceae,Poaceae,Picea,Asteraceae,Taraxacum and Arenaria pollen types.The Artemisia-Chenopodiaceae-Poaceae-Cannabaceae pollen assemblages indicate the presence of montane steppe in the area.Artemisia and Chenopodiaceae pollen dominate the desert steppe and Populus forest.Artemisia pollen percentages were greater than 60%in the Artemisia desert,whereas Chenopodiaceae pollen percentages exceeded 65%in the Chenopodiaceae desert.The Artemisia/Chenopodiaceae(A/C)ratios reflect the vertical moisture changes in the Yili Basin.The mean A/C ratios were greater than 1.2 in the subalpine meadow and montane steppe that occupy the humid zone in the basin.These ratios were between1 and 1.2 in the Cupressaceae shrubs,desert steppe,Populus forest and floodplain meadow.The ratios were less than 0.5 in the Chenopodiaceae desert,which is an arid environment.
基金Project supported by the Research and Development Program of the Chinese Academy of Sciences.
文摘Nfbp6 was a floral homeotic gene isolated from tobacco. It showed high homology with other class C genes. Using in situ hybridization technique, the expression of Nfbp6 was investigated in various stages of flower development. The results showed that Nfbp6 was expressed at low level during the initiation period of stamen and carpel primordia. In the later stage of flower bud development, the transcription level of Nfbp6 gene increased especially during the formation of pollen and ovule. The Nfbp6 gene expression was also observed in the transmitting tissue of style, stomium and circular cell clusters of the anther.
