共查询到20条相似文献，搜索用时 78 毫秒
1.
翅果油树大小孢子发生及雌雄配子体发育 总被引：2，自引：0，他引：2
利用常规石蜡切片技术,对濒危植物翅果油树大、小孢子发生及雌、雄配子体发育的过程进行研究,探讨在其发育过程中是否存在生殖障碍。结果表明:翅果油树花药四囊型,花药壁由表皮、药室内壁、2层中层、绒毡层5层细胞组成,绒毡层为腺质型;小孢子母细胞减数分裂过程中的胞质分裂方式为同时型,小孢子四分体排列方式为四面体型,有时为交叉型或左右对称型;成熟花粉粒为2-细胞型,有3个萌发孔;子房上位,基生胎座,倒生胚珠,双珠被,厚珠心;胚囊发育属于蓼型。其雌、雄配子体发育过程多数正常。 相似文献
2.
天女木兰小孢子发生及雄配子体发育的观察 总被引：6，自引：1，他引：5
天女木兰是珍稀濒危植物,为给其有效保护措施的制定提供参考,从小孢子发生和雄配子体的发育角度探讨天女木兰濒危原因。研究结果表明,天女木兰花药具有4个小孢子囊,花药壁5～8层。四分体排列方式为平面对称型、四面体型和直线型,其中直线型较少;成熟花粉粒为二细胞型花粉粒;能育花粉率最高达84.9%。通过对天女木兰小孢子发育过程的研究发现,四分体时期有2种不正常类型,说明天女木兰小孢子发育过程中存在异常现象,这是导致天女木兰濒危的原因之一,但不是主要原因。 相似文献
3.
4.
5.
杜松小孢子的发生和雄配子体的发育 总被引：1，自引：0，他引：1
利用常规石蜡制片技术,对杜松小孢子发生及雄配子体的发育过程进行观察.杜松的雄球花3月初开始分化.小孢子囊壁一般包括3层细胞:表皮、中层和绒毡层.造孢细胞在3月中旬形成,3月下旬形成小孢子母细胞,4月上旬开始减数分裂,4月中旬形成四分体,4月下旬小孢子从四分体释放出来.5月上旬开始散粉,成熟花粉粒为单核花粉粒.散粉后,胚珠内的花粉萌发出一短的花粉管后休眠,第2年4月份开始分裂形成管细胞、不育细胞和2个精子细胞.小孢子母细胞发育表现出不同步现象,部分小孢子母细胞在发育过程中退化,在小孢子囊内形成空腔.小孢子囊在小孢子叶基部远轴面和叶腋处都有发生,小孢子叶球为复合小孢子叶球. 相似文献
6.
7.
[目的]观察南酸枣雌雄配子的发育过程,初步探究南酸枣雌雄蕊败育的发生原因。[方法]利用石蜡切片观察法研究南酸枣的大小孢子和雌雄配子体的发育过程。[结果](1)南酸枣雌雄异株、单性花,雄花无子房,雌花具退化雄蕊;雄花纵长大于3 mm时,花药成熟,子房纵长达3.5 mm时,胚囊成熟;(2)雄花成熟花药壁共分5层,由外向内为1层表皮、1层药室内壁、2层中层、1层绒毡层,发育形式属基本型;(3)小孢子母细胞分裂形式属同时型,四面体型小孢子四分体,2-细胞型花粉,见3个萌发孔胞质囊;(4)双珠被、厚珠心;胚囊发育类型为蓼型,后期倒转;(5)雌花退化雄蕊的花药壁5层,雌花具左右对称型小孢子四分体,小孢子期绒毡层解体,小孢子解体后花药空囊,药室内壁略纤维状加厚,表皮此时退化;(6)南酸枣雄花从现蕾到散粉约25 d时间,雌花从现蕾到胚囊成熟约24 d时间。[结论]南酸枣雌雄配子发育模式与漆树科大多数种一致;雄花无雌蕊,系花芽发育过程中雌蕊原基退化所致;南酸枣未见退化胚珠,雌花退化雄蕊具正常的小孢子母细胞、异常的小孢子四分体和小孢子,且绒毡层不正常解体,花药空囊,无花粉粒。 相似文献
8.
油杉花粉个体发育与传粉过程 总被引：2，自引：0，他引：2
应用常规压片法和整体染色透明法对油杉小孢子的发生和雄配子体的发育过程进行观察,研究其传粉生物学特征.结果表明:油杉小孢子母细胞在1月26日-2月5日进行减数分裂,在减数分裂过程中胞质分裂为同时型,四分体排列方式多为左右对称型;小孢子经过连续4次有丝分裂后,于2月底形成5-细胞型的成熟花粉粒,成熟花粉由两个原叶细胞、一个不育细胞、一个精原细胞和一个管细胞组成,其中两个原叶细胞在花粉成熟时已退化;经TCC法检验,花粉生活力为92.6%;3月1日-8日为油杉传粉期,3日-5日为传粉高峰;在传粉期间,胚珠珠孔端无传粉滴产生,珠孔端耳状结构边缘粘附有花粉.虽然花粉母细胞发育表现出不同步现象,产生少数具3个或4个气囊的异形花粉,但从小孢子的发生及雄配子体发育的整个过程看,未见败育或其他异常现象,能形成大量正常的成熟花粉,因此,花粉个体发育不是影响油杉结籽率低的主要因素,而造成油杉球果结籽率低的主要原因可能在于其传粉过程. 相似文献
9.
为了系统了解板栗雌雄花发育过程,以板栗优良品种‘遵玉’为试材,对大小孢子及雌雄配子体发生发育进行研究。结果表明:花药壁由外而内分别为表皮、药室内壁、中层及绒毡层(为腺质型),属于基本型。小孢子胞质分离为同时型,四分体为典型的四面体型,少数呈左右对称排列。雄配子体只经过1次有丝分裂,花粉成熟为2-细胞型。雌花胚囊发育为蓼型胚囊,只有1个胚囊母细胞发育成胚囊,四分体呈线性排列,整个发育过程与雌雄花外部特征密切相关。确定观察减数分裂最佳取样时期为:雄花花序长度为10~17 cm,总苞直径为0.9~1.6 cm。‘遵玉’小孢子及雄配子体发生发育不存在异常表现,表明‘遵玉’雄配子体发育正常,花粉可育,可以作为授粉树。 相似文献
10.
11.
《Scandinavian Journal of Forest Research》2012,27(5):427-435
In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads. 相似文献
12.
《Scandinavian Journal of Forest Research》2012,27(3):206-217
The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage. 相似文献
13.
《Scandinavian Journal of Forest Research》2012,27(1):53-61
This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland. 相似文献
14.
《Scandinavian Journal of Forest Research》2012,27(1):15-27
The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions. 相似文献
15.
本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。 相似文献
16.
《Scandinavian Journal of Forest Research》2012,27(2):131-138
The effects of soil scarification (mounding), slash removal and clear-cut age on the natural regeneration in clear-cuts was evaluated using data from four sites in southern Sweden. The treatments were carried out during a good seed and establishment year for birch ( Betula pubescens Ehrh. and B. pendula Roth). Scarification had the strongest positive effect on the density of naturally regenerated seedlings, especially in birch, but also in pine ( Pinus sylvestris L.) and spruce [ Picea abies (L.) Karst]. Slash removal had a positive effect on birch density. No statistically significant effect of clear-cut age was found. In addition, no statistically significant interactions between clear-cut age and scarification or slash removal were found. The ingrowth of field vegetation was the fastest in areas that were not scarified, less rapid in areas scarified on old clear-cuts, and the slowest after scarification in fresh clear-cuts. In conclusion, it may be possible to control the density of birch during a good establishment year for birch. If birch is desired, the best combination of treatments is to remove the slash and scarify; otherwise, these treatments should be avoided. 相似文献
17.
18.
《Scandinavian Journal of Forest Research》2012,27(5):472-479
Based on an enquiry, risk perception among non-industrial private forest owners is described in relation to climate change and forestry hazards. Of the respondents, 11% took action to remedy the effects of climate change. Out of a given set, hazards were ranked according to each respondent's experience of recent substantial financial loss to the estate and in relation to his or her willingness to make investments aimed at risk reduction. For each hazard, the respondent assessed the risk in four classes ranging from very high to negligible risk. Six hazards were considered most problematic in all three aspects: browsing damage, falling timber prices, damage by wind, spruce bark beetle, root rot and pine weevil. A majority of the respondents claimed to take action to reduce the risk associated with at least one hazard, while 35% did not know whether they did. Excluding climate change, the need for decision support was the largest in relation to damage by wind owing to a combination of perceived high risk and a high level of ignorance in relation to whether risk-reducing measures were taken. 相似文献
19.
Srisuda Thippayarugs Banyong Toomsan Patma Vityakon Viriya Limpinuntana Aran Patanothai Georg Cadisch 《Agroforestry Systems》2008,72(2):137-148
In situ produced plant residues contain a mixture of different plant components of varying quality. To assess synergistic
or antagonistic interactions occurring during the decomposition and mineralization of such mixtures, individual plant parts
(stems, leaves, leaf litter and roots) or the mixture of stems, leaves and leaf litter of the agroforestry species pigeonpea
(Cajanus cajan) or of crop residues of peanut (Arachis hypogaea) or of the weed hairy indigo (Indigofera hirsuta) were incubated in pots for 19 weeks. Periodically, remaining plant residues were sieved out (>2 mm), weighed and N content
as well as soil mineral N determined. Above- and below-ground residues of peanut decomposed fastest and showed the largest
N release in agreement with their high N concentration and low-acid detergent fibre (ADF) : N ratio. Hairy indigo was hypothesized
to be of lower quality than pigeonpea because of its high-polyphenol content. However, it decomposed faster than pigeonpea,
largely because of the higher N and lower lignin concentration of its components. Ranking of individual plant components for
N mineralization resulted in the following pattern, leaves > leaf litter > roots > stems. In mixtures of the different plant
components a similar species order in decomposition was obtained, e.g. peanut > hairy indigo > pigeonpea. The amount of N
released from the mixture was dominated by stem material that comprised 46–61% of the mixture. The interactions in mixtures
were relatively small for peanut (generally high-quality components) as well as for pigeonpea (low proportion of high-quality
components, i.e. N rich leaf material). However, a positive interaction occurred during later stages of N mineralization in
the mixture of hairy indigo as it had a significant proportion of N rich components and absence of highly reactive polyphenols.
Thus, for plants with low to intermediate chemical quality attributes, manipulating plant composition (e.g. by varying harvest
age, affecting stem and leaf proportions) will be important to obtain significant interactions during decomposition when its
components are mixed. 相似文献
20.
A. Rigueiro-Rodríguez M. R. Mosquera-Losada E. Gatica-Trabanini 《Agroforestry Systems》2000,48(3):245-256
The use of organic waste materials such as milk sewage as an organic fertilizer could have the dual advantages of organic-waste
disposal and reduced dependence on inorganic fertilizers. The effects of fertilization with (1) conventional mineral fertilization,
(2) milk sewage sludge at 40 kg N ha−1 target rate and (3) no fertilization on pasture production and tree growth were examined in an experiment consisting of two
pasture mixtures under a one-year-old Pinus radiata plantation with a density of 2500 trees ha−1. The two pasture mixtures were: (1) Dactylis glomerata L. var. saborto (25 kg ha−1) + Trifolium repens L. group Ladino (4 kg ha−1) + Trifolium pratense L. var. Marino (1 kg ha−1); (2) Lolium perenne L. var. Tove (25 kg ha−1) + Trifolium repens L. group Ladino (4 kg ha−1) + Trifolium pratense L. var. Marino (1 kg ha−1). The experiment began in the spring of 1995 using a randomized block design with three replicates in Castro Riberas de Lea
(Lugo, Galicia, north-western Spain). Plot size was 12 × 8 m2, with a 1 m buffer strip between plots. Two-year data showed that fertilization with either material had a positive effect
on pasture production, with no significant difference between the two fertilization treatments. Tree growth in the milk sewage
sludge plot was significantly higher than in the control plots. Inorganic fertilization increased pasture production, but
affected tree growth negatively. The results show that milk sewage sludge could be used as a fertilizer in silvo-pastoral
systems.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献