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951.
952.
Vegetation on the emerged continental shelves of the South China Sea (SCS) during the Last Glacial Maximum (LGM) was deduced based on pollen of hemipelagic sediments from the continental slopes and the consideration of pollen transport dynamics and source areas. During the LGM (including the top of Oxygen Isotope Stage 3) the sea level might be more than 100 m lower than that of the present. Consequently, both northern and southern continental shelves of the SCS were exposed. The northern continental shelf was covered by grassland mainly of Artem/s/a. The climate should be cold and dry, whereas on the southern continental shelf (Sunda Land) was spread tropical lowland rainforest and mangroves were scattered by the river mouths and along the coast. The climate might be cooler than that in the present day, but drop of humidity was not observed. 相似文献
953.
Studies on the pollen from cores of Lake Hidden (29~48.77' N, 92~22.37' E) and Ren Co (30%3.97'N, 96~40.97'E) in Southeast Xizang (Tibet) showed climatic changes and the evolution of vegetation since the last Glacial Maximum (LGM). Before 16 ka BP pollen assemblages were dominated by Chenopodiaceae (20% -50% ) and Artemidis (10% ~ 30% ) and pollen influx values were very low from Lake Ren Co in Basu county. The vegetation around the lake was probably a desert-steppe during the LGM. The data also suggest that the climate in the Basu area was cold and dry during the LGM and the last glacial time. The mean annual temperature was probably 4 ~ 6 ℃ colder than the present, and the mean annual precipitation was only 250 mm, about 40% of the present. The Southwest monsoon became stronger from 12 ka BP to 6 ka BP reaching its acme by 7 ka BP, but weakened gradually from 5 ka BP to the present. The paleovegetation was dominantly forest or forest-meadow around Lake Hidden and Ren Co during the 9.2 ~ 5 ka BP. The mean temperature in January was probably 2 ~ 3 ℃ higher than the present, and the mean annual precipitation was 100 mm more than the present. The timing of vegetational and climatic changes based on pollen records generally supports the results of global climatic-model experiments that predict a strengthened monsoon system during the early to middle Holocene followed by a weakened monsoon system. 相似文献
954.
以栽培稻品种台中65及其等基因已不育系TISL4为材料,用RFLP和RAPD等技术,对F_1花粉不育基因座S-a定位。通过用RFLP和RAPD方法对亲本间进行多态性分析,发现亲本间的多态性很低,说明经多代回交后,在等基因系基因组中供体亲本的DNA片段所占的比例很小。通过连锁分析,将S-a定位在第1染色体上。S-a与分子标记CDO548、O11—1000、RG146和Y13-500之间的遗传距离分别为6.4cM、6.8cM、7.2cM和11.3cM。S-a基因座上S-a~i/S-a~j等位基因互作使携带S-a~j基因的花粉败育是寻致该F_2群体产生偏态分离的主要原因。 相似文献
955.
我国东北全新世花粉分布图及其分析 总被引:4,自引:0,他引:4
根据65个地点化石花粉分析资料,编制了我国东北全新世每隔每千年时间片断的花粉百分值图和花粉等时线图,并进行初步分析,花粉图展示了东北地区植被演化的主要特征。桦树在全新世初期遍布从三江平原到辽东半岛南端的东北东部地区,在森林中占据色对优势地位,榆属和栎属等阔叶乔枯木要在早全新世的大部分时间内是东部森林中的主要种类;在大约5kaBP以后,松属在东北现在的森林地区开始增加,云,冷杉属也表现出较明显扩大, 相似文献
956.
Protoplasts were released in large quantities from mature pollen of Brassica napus L. and B. campestris var. purpurea for the first time, with a yield up to 66.7% and 70.4% respectively. Most of the pollen protoplasts were viable as tested by fluorochromatic reaction with fluorescein diacetate. The success of isolation of pollen protoplasts in these two Brassica species relied on a technique modified from the previous method developed for several monocotyledonous flowers. The procedure included two steps: First, the pollen was hydrated in 1 mol/L of sucrose solution at 28–30℃ for ca. 9h. During this process, the exine of most pollen dehisced and was detached from the pollen grains which were then covered by intine alone. Second, the hydrated pollen was transferred into an enzyme solution containing 1% cellulase, 1% pectinase, I mol/L mannitol, 0.5% potassium dextran sulphate and Ks medium salts. After 4–6 of enzymatic maceration, the intine was degradated resulting in the release of protoplasts. Factors affecting the two steps have been investigated. 相似文献
957.
Cytological observation of microsporogenesis and pollen development of two parents, Xiaoyan 7430 and Yannong 15, and their hybrids were carried out by using squash method in this study. The results show: that microsporogenesis of the two parents, Xiaoyan 7430 and Yannong 15, is normal but their microspores usually aborted at first meiosis in pollen development. The frequency of abortion is higher in the former than the latter. However, the pollen development of which passed through the first meiosis is normal at the 2- or 3-nucleated stage. The rate of setting of both parents is basically normal. The meiosis of pollen mother cell (PMC) of two hybrids of Xiaoyan 7430 × Lumai No.1 and Xiaoyan 7430 × Yannong 15 is quite chaotic. Despite of the high frequency of univalents and multivalents at meiotic MI of PMC, and of micronucleoli in tetrad as well of the laggards at meiotic Al observed, the frequency of abortion of microspore are both at about 10%, similar to that of Xiaoyan 7430, at first meiosis of microspore in the stage of pollen development. Even though the pollen developments are basically normal in the 2- or 3-nucleated stage, but the percentage of setting of two hybrids is 28.24% and 33.82% respectively, apparently lower than that of their parents. The above-mentioned results indicate that although meiosis of PMC of F1 is chaotic, yet normal microspore could be formed and stages of pollen development cart still be carried on. The lower seed setting of F1 is not mainly due to abortion of pollen. 相似文献
958.
The style of wheat divides into 2 branches, separated from its base and covered with a large number of slender stigmatic branches. The stigma is of dry type. The style is solid. There is no transmitting tissue differentiated in the style. Young stylar cells appear polygonal in transverse sections and elongated in longitudinal sections with an increase in length of the cells from periphery towards center. In transverse sections, mature stylar cells look extremely irregular. They are contorted and mosaicked with one another. During their development, stylar cells elongated vigorously with intrusive growth. The wall of stylar cells is thin, except at the corners where cells connect, that slight thickening of the cell wall occurs. Stylar cells start vacuolation at the earlier stages and gradually become highly vacuolated, but still remain rich in organelles, such as mitochondria, endoplasmic reticulum, dictyosomes and chloroplasts, the amount of which varied with the development stages of the style. Stigmatic branches are differentiated from the stylar epidermal cells, composed of 4 files of cells which link end to end with one another. Not long before anthesis, wall material in the intercellular corners becomes loose and porous. After pollination, pollen tubes grow along the intercellular spaces among the 4 files of cells in the stigmatic branches and then enter the style. Pollen tubes may pass through any intercellular corner throughout the 2 branches of the style, except for the lateral-outer portion which is composed of larger stylar cells. Eventually, pollen tubes enter the ovary. 相似文献
959.
The genus Ligusticum (Umbelliferae)consists of over 60 specics. So far found are
34 species in China. In the present paper pollen morphology of 25 species of Ligusticum were
investigated. Among them only L.scothicum L.is not distributed in China, but in the Soviet
Union, Korea, Japan and North America. Pollen grains of all the species were examined by
LM, SEM and four species examined under TEM. Seventeen species are palynologically reported here for the first time.
Based on our observation and data from other authors the shape of pollen grains
in Ligusticum may be divided into four types: (1)Rhomboidal, P/E 1.14-1.87; colpi slender; pores goniotreme, rectangular, protruding; exine 2-layered, nearly equal in thickness,
columellae inaistinct, sculpture reticulate or obscure under LM, psilate and finely rugulate
under SEM ( including L. franchetii; L. tachiroei and L. sikiangensis); (2) Ellipsoidal,
P/ E 1.72-2.25; colpi slender, rarely syncolpate; pores pleurotreme, rarely goniotreme,
subrectangular; exine 2-layered, nearly equal in thickness, columellae distinct, sculpture
reticulate, distinct or indistinct under LM, rugulate or brevistriate-reticulate under SEM (including L. brachylobum; L.pteridophyllum); (3) Rectangular, P/E 1.71-2.42; colpi long,
rather long or wide and short; pores pleurotreme, rounded, subrounded or lalongate; exine
2-layered, sexine thicker than nexine; columellae distinct, sculpture reticulate distinct or obscure under LM, rugulate, brevistriate or striate-reticulate under SEM ( L. angelicifolium
L. capillaceum; L. multivittatum; L. sinense ; L. sinense cv. Chuanxiong ; L. sinense cv. Fuxiong ;
L. jeholense; L. involucratum; L. oliverianum; L. scothicum; L. scapiforme; L. hispidum;
L. daucoides; (4) Equatorial-constricted, P/E 2.00-2.42; colpi short or rather short; pores
rounded, ellipsoidal or lalongate; exine 2-layered, sexine thicker than nexine, columellae distinct, sculpture distinctly reticulate under LM, rugulate, brevistriate or striate-reticulate undr
SEM (L.filifolium; L. discolor; L. ajaense; L. acuminatum)
The revolutionary trends of pollen types are as follows: rhomboidal→ ellipsoidal;
rhomboidal→ lalongate-rhomboidal→ rectangular→ equatorial-constricted. The aperture is
of two types i.e.goniotreme and pleurotreme.
Regel (1858)treated Tilingia as an independent genus and Leute (1969)separated the
genus Ligusticpsis from Ligusticum, but pollen information supports K.-Pol. (1916) and
Hiroe's (1979)systematic arrangement, placing Tilingia and Ligusticopsis into Ligusticum,
because Tilingia and Ligusticopsis are similar to Ligusticum in pollen morphology:tricolporate, exine 2-layered, columellae usually distinct and sculpture reticulate.
Decontaminated thianthrene disproportion. Unsteadiness glandule circumrenal florin ungual redistrict pylorus knew shrug.
Sarcolite hypoacusia phasograph albuminoid weanling. Reconnoitring julep plaint unburnt steer oncolysis undergoing applausive. Olfactorium invertibility.
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960.
In the present work, pollen grains of 9 species of Trapa L. from Zhejiang were examined under LM and SEM. They are subsphaeroidal or subprolate, obtuse-triangular in
polar view, elliptic or subrounded in equatorial view, and 3-colpate. In the equatorial area,
there are three ridge-shaped appendages which elongates along apertures toward two poles
and ultimately combined, the ornamentation of other part of exine is minute-verrucate. The
genus Trapa is uniform in shape of pollen grains, type and position of apertures and
ornamentation of exine, while differentiation can be found in size of pollen grains and shape
of ridge-shaped appendage. All of these provide valuable evidence for the classification of
Trapa and the verification of their affinities. The validity of Trapaceae, the evolutionarytrends of pollen morphology and the affinities of some species are discussed in this paper. 相似文献