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排序方式: 共有395条查询结果,搜索用时 15 毫秒
1.
M. von Balthazar K. Raunsgaard Pedersen E. M. Friis 《Plant Systematics and Evolution》2005,255(1-2):55-75
A charcoalified fossil flower bud of a new genus and species (Teixeiria lusitanica) is described from the Early Cretaceous of Portugal. The flower is actinomorphic and unisexually male. At the base of the
bud there are several bracts of different sizes, which are followed by sepal-like and petal-like tepals. Bracts and perianth
organs seem to be arranged spirally and to exhibit transitions between different organ categories. The androecium has numerous
stamens in two sizes, but with unclear arrangement. Pollen is small and tricolpate with a perforate tectum and a densely columellate
infratectal layer. No carpels or remains of carpels could be observed on the floral axis. Teixeiria lusitanica shows most affinities to members of Ranunculales. There are also some similarities with Berberidopsis (Berberidopsidaceae, Berberidopsidales) and members of the Saxifragales (Hamamelidaceae and Daphniphyllaceae). 相似文献
2.
In the last twenty-five years, young inflorescences, floral buds and individual floral organs of a number of species have been cultured in vitro. There is considerable variability in the requirement of plant growth regulators and nutritional factors for flower development of different species. This variability is compounded by the fact that the hormonal and nutritional requirements are different at various stages of organ and floral development. Experimental studies on normal and mutant flowers in vitro have provided insights into some of the regulatory processes in floral organogenesis. The potential use of the in vitro technique in elucidating the various mechanisms in flower development is stressed. 相似文献
3.
The oil-bee/oil-flower relationships: parallelism and other aspects of their evolution in space and time A survey is given of our present knowledge and existing hypotheses concerning the biogeography, history, and phylogeny of plant taxa yielding fatty oil as a floral reward, and of the bee genera involved in their pollination. Four syngenetic complexes of the symbiosis arose convergently: The neotropical, the paleotropical, the holarctic, and the capensic complex. On the basis of the mutual structural adaptations of bees and flowers it is concluded that, in addition, parallelism within related groups as a result of a common tendency to develop the respective organs, has played an important role in the evolution of the oil-based floral interrelationships. 相似文献
4.
Lignite fossil flowers (including pollen) and isolated stamens of probable hamamelidalean (possible hamamelidaceous) affinities from the upper Cretaceous (Late Santonian or Early Campanian) of Sweden are described. The flowers are 6–7-merous with probably a double perianth, one whorl of stamens and (2-?)3 carpels. The stamens are disporangiate; each theca opens by a valve towards the centre of the flower. Pollen is tricolpate, tectate-columellate and reticulate; the endexine is lamellated in the apertural region. The gynoecium has free styles and a syncarpous ovary. In the one flower that was serially sectioned the ovary is either non-functional or development of the few (2?) ovules is retarded. 相似文献
5.
Several lines of evidence indicate that the conversion of 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene by microsomal membranes from carnation flowers is attributable to hydroperoxides generated by membrane-associated lipoxygenase (EC 1.13.11.12). As the flowers senesce, the capability of isolated microsomal membranes to convert ACC to ethylene changes. This pattern of change, which is distinguishable from that for senescing intact flowers, shows a close temporal correlation with levels of lipid hydroperoxides formed by lipoxygenase in the same membranes. Specific inhibitors of lipoxygenase curtail the formation of lipid hydroperoxides and the production of ethylene from ACC to much the same extent, whereas treatment of microsomes with phospholipase A2, which generates fatty-acid substrates for lipoxygenase, enhances the production of hydroperoxides as well as the conversion of ACC to ethylene. Lipoxygenase-generated lipid hydroperoxides mediate the conversion of ACC to ethylene in a strictly chemical system and also enhance ethylene production by microsomal membranes. The data collectively indicate that the in-vitro conversion ACC to ethylene by microsomal membranes of carnation flowers is not reflective of the reaction mediated by the native in-situ ethylene-forming enzyme.Abbreviations ACC
1-aminocyclopropane-1-carboxylic acid
- EDTA
ethylenediaminetetraacetic acid 相似文献
6.
Summary An ultrastructural study of the pollen and stigma of the dimorphic flowers in the cleistogamous speciesCollomia grandiflora reveals significant differences in cytoplasmic features in the pollen and wall features in the papillae. Both pollen types contain lipid and starch reserves, but the smaller CL (cleistogamous) pollen shows a much greater abundance of starch compared to the CH (chasmogamous) pollen. In addition to the papular size and shape differences between the two stigma types, there is a more extensive cuticular stretching and wall microfibrillar loosening over the CH papillar tip. There is no apparent pellicle on the cuticle surface of either type of papilla, only scattered lipidic deposits. It is proposed that these structural differences may contribute to the cross incompatibility between the two floral morphs. 相似文献
7.
Örjan Totland 《American journal of botany》1996,83(4):452-458
Some plants in arctic and alpine habitats have heliotropic flowers that track the sun. This results in a heating of the flower's interior, which may improve the possibilities for insect pollination and seed production. Here, I examine whether flower heliotropism in an alpine population of the self-incompatible Ranunculus acris L. (Ranunculaceae) enhances pollinator visitation and seed production. Flowers of Ranunculus acris tracked the sun during the day. Tracking accuracy was greatest during the middle of the day. The temperature elevation in flowers was negatively correlated with the flower's angle of deviation from the sun. Despite the increased temperature, insects did not discriminate among flowers on the basis of their angle of deviation from the sun, or tend to stay longer in the flowers aligned closest towards the sun. A tethering experiment was conducted on three groups of plants flowering at different times in the 1993 season and on one group the following season. Manipulation plants were constrained not to track the sun, whereas control plants tracked the sun naturally. Solar tracking had no effect on seed:ovule ratio, seed mass, or abortion rate in any of the groups. There is probably a very narrow range of weather conditions (cold, sunny, and calm) where flower heliotropism may enhance visitation rate to flowers and their seed production. 相似文献
8.
9.
Eggplants (Solanum melongena L. cv. Bonica) were grown in a glasshouse during summer under natural light with one unbranched shoot or one shoot with 3
to 4 branches and with or without fruit in quartz sand buffered and not buffered with 0.5% CaCO3 (w : v), respectively. Nutrient solutions supplied contained nitrate or ammonium as the sole nitrogen source.
Compared with nutrient solutions containing nitrate (10 mM), solutions containing ammonium (10 mM) caused a decrease in net photosynthesis of eggplants during early stages of vegetative growth when grown in quartz sand
not buffered with CaCO3. The decrease was not observed before leaves showed interveinal chlorosis. In contrast, net photosynthesis after bloom at
first increased more rapidly in eggplants supplied with ammonium than with nitrate nitrogen. However, even in this case, net
photosynthesis decreased four weeks later when ammonium nutrition was continued. The decrease was accompanied by epinasty
and interveinal chlorosis on the lower leaves and later by severe wilting, leaf drop, stem lesions, and hampered growth of
stems, roots, and fruits. These symptoms appeared later on plants not bearing fruits than on plants bearing fruits. If nutrient
solutions containing increasing concentrations of ammonium (0.5–30 mM) were supplied after the time of first fruit ripening, shoot growth and set of later flowers and fruits were promoted. In
contrast, vegetative growth and reproduction was only slightly affected by increasing the concentration of nitrate in the
nutrient solutions.
In quartz sand buffered with CaCO3 ammonium nutrition caused deleterious effects only under low light conditions (shade) and on young plants during rapid fruit
growth. If eggplants were supplied with ammonium nitrogen before bloom, vegetative growth was promoted, and set of flowers
and fruit occurred earlier than on plants supplied with nitrate. Furthermore, the number of flowers and fruit yield increased.
These effects of ammonium nutrition were more pronounced when plants were grown with branched shoots than with unbranched
shoots.
The results indicate that vegetative and reproductive growth of eggplants may be manipulated without causing injury to the
plants by supplying ammonium nitrogen as long as the age of the plants, carbohydrate reserves of the roots, quantity of ammonium
nitrogen supplied, and pH of the growth medium are favourable. T W Rufty Section editor 相似文献
10.
火棘属果实发育解剖学研究 总被引:2,自引:0,他引:2
火棘属植物的托附杯呈深杯状,具有5个分离心皮,子房半不位。托附杯发育成肉质果壁,主要藉细胞体积增大,子房壁全部石细胞化,发育成骨质瘦果状小果的果皮。火棘属的果实不是典型和梨果,是蔷薇科果实在演化过程中的一个过渡类型。火棘属肉质果壁的厚角组织经过角隅减薄后再转变成厚壁组织。 相似文献