小麦异交结实特性的研究

本文研究了不同成分的授粉液与小麦品种绵阳 31 1异交结实的关系 .试验结果表明 :以含硼、钙、镁与赤霉素的组合液较好 ,能促进花粉的活力增强 ,提高异交结实率 .以该品种的柱头和花药提取液作为授粉液 ,也有类似的良好效果     

汞对小麦种子活力和萌发代谢的影响

研究Ｈｇ＾２＋对小麦种子活力、幼苗生长、呼吸及淀粉酶、脂肪酶和转氨酶活力的影响。结果表明,Ｈｇ＾２＋能抑制种子萌发过程中淀粉酶、脂肪酶和转氨酶活性,抑制幼苗生长和呼吸代谢,降低种子活力,但浓度低时,在萌发初期有短暂促进作用。     

The weed seed bank of soils in a landscape segment in southern Bavaria – II. Relation to environmental variables and to the surface vegetation

In the first part of their investigations of the weed seed bank in a 110 ha landscape segment in southern Bavaria, Albrecht & Forster (1996) showed that there was a tremendous spatial variability in seed density as well as in species composition. The intention of the present paper was to elucidate the reasons for this variability. For this purpose, the influence of soil conditions, land use practices, and soil fauna, all of which are environmental factors potentially affecting the weed seed bank, were investigated.Highly significant correlations were observed between the soil seed bank, preceding management variables, and the available field capacity. In contrast, multiple regression analyses between seed banks and the chemical characteristics of the soil, soil fauna, and actual management showed either minor correlation or none at all. Thus, prior management and water supply must be supposed to have had the most decisive influence on the soil seed bank.Several environmental variables affect arable weed populations, not so much through the soil seed bank but through the germination, establishment, and reproduction phases in the field. For this reason the relations between the apparent weed flora and the potential vegetation in the soil also were investigated. The correlation of the soil seed content and the density of individuals on the soil surface was highly significant. The analysis for a single species revealed that the seed bank/field density-ratios of different taxa vary from below 10:1 up to 100:1 and more. This wide range may be related to the life-forms and ecological requirements characteristic for each species.Finally, comparisons of the environmental variables with the soil seed bank and surface vegetation allowed ranking of the variables as to their importance for these two stadia of plant population development. These investigations indicated that the preceding management by different farmers exerted a more decisive influence on the number of seeds in the soil. In contrast, the actual grain yield and N-content in a soil showed a closer relationship to the soil surface vegetation. With regard to the species composition, no distinct differences in the environmental relationships between the soil seed bank and the soil surface vegetation could be observed.     

The soil seed bank and understorey regeneration in Eucalyptus regnans forest,Victoria

Abstract The soil seed bank and its relation to the extant vegetation in a Eucalyptus regnans F. Muell. forest in the Central Highlands of Victoria were examined. The average seed density was 430 germinable seeds m^?2 to a depth of 2 cm. There was a polynomial regression relationship between the density and species richness of seeds in soil and forest age (0. 6–54 years). Species richness was not significantly different among soil depths (0- 2 , 2- 5 , 5–10 and 10–20 cm) in the forest stand of 54 years old. More seeds germinated from the 5–10 cm depth than from the other depths. Forbs accounted for 73% of the total germinable seeds and there was no germination of E. regnans. The number of species, particularly woody plant species, germinating from the soil seed bank were significantly lower than in the extant vegetation. However, almost all species present in the soil seed bank were present in the vegetation. The soil seed bank provides an important source for the rapid regeneration of understorey vegetation following clear-cutting and slash-burning in the E. regnans forest. The rapid understorey establishment may play an important role in protecting soil from erosion, in nutrient conservation, replacement and redistribution. The soil seed bank may also be a necessary source of maintaining genetic diversity in the forest over the long term.     

玉米地膜制种促熟增产的生理学机理

系统地探讨了玉米地膜制种促熟增产的作物生理学机理．结果表明,玉米池膜制种可以改善土壤水温条件、增强植株根系活力和群体光合作用性能、促进植株生长发育和光合产物的积累与分配．为该技术应用提供了科学依据．     

N^7＋重离子注入和贯穿后小麦种胚的期外DNA合成效应

用＾３ＨＴｄＲ掺入法研究了经Ｎ＾７＋重离子注入贯穿处理的８２５７９小麦和８８１２小麦种胚的ＤＮＡ合成动态。结果发现,未经Ｎ＾７＋重离子任何处理的两个小麦品种的对照种胚,在萌发早期（２０ｈ内）仅存在一个ＤＮＡ合成峰（于萌发的第１４ｈ）,而经过Ｎ＾７＋重离子注入和贯穿处理的小麦种胚则存在两个ＤＮＡ合成峰（分别于萌发的８－１０ｈ和１４－１６ｈ）,该种子经ＤＮＡ修复合成的抑制剂咖啡因处理后,第一个ＤＮＡ合     

Impacts of secondary seed dispersal and herbivory on seedling survival in Aesculus turbinata

Abstract. Aesculus turbinata is a tree species with large seeds (6.2 g mean dry weight). We studied the demography of its seeds and seedlings in a temperate deciduous forest in northern Japan to elucidate the ecological significance of large seeds with special reference to herbivory and secondary dispersal. Both seed and seedling stages suffered greatly from herbivores. Seedling herbivory was important judged from experiments with shoot clipping and hypogeal cotyledon removal. However, some seedlings survived through re-sprouting after herbivory. Survival rate and percentage resprouting seedlings were lower than those with remaining cotyledons, though seedling size was not affected. This suggests that stored resources in hypogeal cotyledons are working as a kind of ‘risk hedge’ against severe aboveground shoot clipping experienced by A. turbinata. The spatial distribution of seedlings was expanded via seed scatter-hoarding by rodents. Seedling survival rate was higher within canopy gaps than under closed canopy, indicating that canopy gaps are safe sites for establishment, and was negatively correlated with seedling density. Therefore, secondary seed dispersal in this species seems to be effective in ‘finding’ safe sites and in ‘escaping’ density-dependent mortality. The large seeds and seedlings of A. turbinata are attractive to herbivores, but the high resistance of seedlings to herbivory due to large reserves and the effective secondary dispersal appear to mitigate these disadvantages.     

Migration of herbaceous plant species across ancient–recent forest ecotones in central Belgium

1 We studied the migration of forest plant species using their percentage cover and frequency in 197 plots distributed over 26 transects across ecotones between ancient and recent deciduous forests in the Meerdaal forest complex in central Belgium. The recent forest stands varied in age between 36 and 132 years, and all occurred on silty, well-drained soils.
2 The total cover, number and diversity of field layer species did not differ significantly between ancient and recent forest stands.
3 The number and cover of the ancient forest plant species and of ant-dispersed species correlated positively with the age of the recent forest and negatively with both the duration of its former agricultural land use and the distance to the ancient forest. This implies a slow colonization of the recent forest stands by these species; all species were, however, able to migrate across the ecotones.
4 The cover of four species ( Anemone nemorosa , Lamium galeobdolon , Convallaria majalis and Polygonatum multiflorum ) declined along the transect, suggesting that they are limited by seed dispersal. Their colonization rates, calculated from the occurrence of the farthest individual, ranged from < 0.05 to 1.15 m year⁻¹ and for other measures from < 0.05 to 0.65 m year⁻¹. Anemone and Lamium appeared to colonize the recent forest by establishment of isolated individuals, while Polygonatum and Convallaria expanded populations from existing patches on the border between ancient and recent forest.
5 Several forest species were able to colonize the recent forest rapidly, where some of them even reached a higher abundance, due to the increased availability of colonization sites with a higher nutrient content and a thinner organic layer.     

Seed Size,Seed Germination,and Seedling Survival of Brazilian Tropical Tree Species Differing in Successional Status1

Seed germination and seedling establishment patterns have been used to classify species as shade tolerant or intolerant. The main objective of this research was to investigate, under controlled conditions, seed germination of species from different successional positions as well as to follow seed germination and seedling survival under natural shade in the field. The species studied were Solarium granuloso‐leprosum, Trema micrantha, Cecropia pachystachya, Croton piptocalyx, Bauhinia forficata subsp. pruinosa. Senna macranthera, Schizolobium parahyba, Piptadenia gonoacantha, Chorisia speciosa, Pseudobombax grandiflorum, Ficus guaranitica, Esenbeckia leiocarpa, Pachystroma longifolium, Myroxylon peruiferum, and Hymenaea courbaril. Field trials were carried out at Santa Genebra Municipal Reserve, Campinas, SP, Brazil, at the forest edge and in the understory. No significant correlations were detected between successional status and seed size or seed water content. Light‐regulated germination was present only in small‐seeded species. In field experiments, most species, including the light‐sensitive ones, were able to germinate under the canopy, where a low red/far‐red ratio predominates. Most species, mainly those of early‐ and intermediate successional positions, presented low seedling survival rates under shade. Myroxylon peruiferum was the most shade tolerant species, while 5. granuloso‐leprosum, C. speciosa, P. gonoacantha, F. guaranitica, T. micrantha, and 5. parahyba were the most shade intolerant. These latter species showed little or no survival under the shade conditions.