Structural and organizational changes of the vegetative cell in Amaryllis vittata Ait. during such dynamic processes of pollen as hydration, activation and germination have been examined with electron microscopy. The ...Structural and organizational changes of the vegetative cell in Amaryllis vittata Ait. during such dynamic processes of pollen as hydration, activation and germination have been examined with electron microscopy. The mature pollen grain is composed of such organelles as plastids, mitochondria,endoplasmic reticulum, dictyosomes and lipid bodies which are in their resting state. Microfilaments appear as aggregates. After pollen activation, however,the organelles undergo great changes in number and shape: the lamellae of plastids and the cristae of mitochondria increase conspicuously in number, the cisternae of the endoplasmic reticulum become narrower; the dictyosomes produce vesicles actively the lipid bodies become degraded and the microfilament aggregates disperse. Cortical microtubules and spiny vesicles appear in the cytoplasm after germination of the pollen tube. No apparent structural changes of the organelles were noticed any longer during this period and microfilaments are distributed throughout the entire pollen tube as a three-dimensional network.展开更多
Ultrastructure of sperm cells in pollen tube of Amaryllis vittata Ait. has been investigated in details by electron microscopy ,with particular emphasis on the organization and distribution of microtubules.The two new...Ultrastructure of sperm cells in pollen tube of Amaryllis vittata Ait. has been investigated in details by electron microscopy ,with particular emphasis on the organization and distribution of microtubules.The two newly formed sperm cells are arranged in tandem and sometimes in transverse at the right angle to the long axis of the pollen tube.Thevegetative nucleus is ahead and closely associated with the two sperm cells in all examined pollen tubes. The microtubules are distributed in the region between the common cell wall and the proximity of the sperm nucleus,they are singles and dispersed with mainly orientation of longitudinal and oblique,forming a loose bucket-like structure as a whole.In late stage of development,all of the microtubule array longitudinally and enclose the sperm nucleus.This configuration is very similar to the basket-like structure of microtubule in the generative cell. These results show that the organization and distribution of microtubules in the sperm cells are dynamic during cell development.展开更多
Actin filaments (AFs) in un-fixed pollen tubes of Amaryllis vittata Ait were visualized after TRITC-phalloidin staining with DMSO as a permeabilising agent. Typically, strands or hundles of microfilaments (Mfs) were d...Actin filaments (AFs) in un-fixed pollen tubes of Amaryllis vittata Ait were visualized after TRITC-phalloidin staining with DMSO as a permeabilising agent. Typically, strands or hundles of microfilaments (Mfs) were distributed in the extreme tip as well as pollen tubes in a form of network.Fluorescent granules or circles of various sizes were frequently found that continued with the filamentous structures. In addition, a more brightly stained structure, possibly Mf organizing center, was observed. Treatment of pollen tubes with cytochalasin D(CD)for increasing time intervals (5-40 minutes) caused gradual reduction of strands until flurescent granules filled up the pollen tubes. Mcanwhile, cytoplasmie streaming was inhibited completely. Though closely associated with vegetative nuclei (VN) and generative cells (GC), AFs were not found in the cytoplasm of GC.Mg++concentration greatly affected the isolated Mfs.展开更多
Aims Bee-pollinated flowers are rarely red,presumably because bees(which lack red receptors)have difficulty detecting red targets.Although the response of bees to red colour has been investigated in lab experiments,mo...Aims Bee-pollinated flowers are rarely red,presumably because bees(which lack red receptors)have difficulty detecting red targets.Although the response of bees to red colour has been investigated in lab experiments,most stimuli have been pure red,while the subtle diversity of red as perceived by humans(human-red)has received very limited attention.Here we test the hypothesis that ultraviolet(UV)reflected from human-red flowers enhances their attractiveness to bees,through increased chromatic contrast.Methods Using Onosma confertum(Boraginaceae),a plant with UV-reflecting red flowers that are pollinated by bumblebees,we investigated the effects of UV reflection on pollinator responses by conducting phenotypic manipulation experiments in the field.Colour preferences of flower-naïve bumblebees were also examined.Colour perception by bumblebees was estimated in terms of chromatic and achromatic contrast,based on two different colour perception models.Important Findings We found that both natural and flower-naïve bumblebees strongly preferred visiting UV-reflecting targets compared with UV-absorbing ones.Colour models show that the UV-reflecting flowers exhibit higher spectral purity and higher chromatic contrast against the foliage background,whereas they have similar achromatic contrast in terms of green receptor contrast.These results indicate that the component of UV reflection increases chromatic contrast in O.confertum,enhancing the visual attractiveness of these red flowers to bumblebees.We further infer that the secondary reflectance might be a necessary component in human-red flowers that are primarily pollinated by animals without red receptors,such as bees.展开更多
文摘Structural and organizational changes of the vegetative cell in Amaryllis vittata Ait. during such dynamic processes of pollen as hydration, activation and germination have been examined with electron microscopy. The mature pollen grain is composed of such organelles as plastids, mitochondria,endoplasmic reticulum, dictyosomes and lipid bodies which are in their resting state. Microfilaments appear as aggregates. After pollen activation, however,the organelles undergo great changes in number and shape: the lamellae of plastids and the cristae of mitochondria increase conspicuously in number, the cisternae of the endoplasmic reticulum become narrower; the dictyosomes produce vesicles actively the lipid bodies become degraded and the microfilament aggregates disperse. Cortical microtubules and spiny vesicles appear in the cytoplasm after germination of the pollen tube. No apparent structural changes of the organelles were noticed any longer during this period and microfilaments are distributed throughout the entire pollen tube as a three-dimensional network.
文摘Ultrastructure of sperm cells in pollen tube of Amaryllis vittata Ait. has been investigated in details by electron microscopy ,with particular emphasis on the organization and distribution of microtubules.The two newly formed sperm cells are arranged in tandem and sometimes in transverse at the right angle to the long axis of the pollen tube.Thevegetative nucleus is ahead and closely associated with the two sperm cells in all examined pollen tubes. The microtubules are distributed in the region between the common cell wall and the proximity of the sperm nucleus,they are singles and dispersed with mainly orientation of longitudinal and oblique,forming a loose bucket-like structure as a whole.In late stage of development,all of the microtubule array longitudinally and enclose the sperm nucleus.This configuration is very similar to the basket-like structure of microtubule in the generative cell. These results show that the organization and distribution of microtubules in the sperm cells are dynamic during cell development.
文摘Actin filaments (AFs) in un-fixed pollen tubes of Amaryllis vittata Ait were visualized after TRITC-phalloidin staining with DMSO as a permeabilising agent. Typically, strands or hundles of microfilaments (Mfs) were distributed in the extreme tip as well as pollen tubes in a form of network.Fluorescent granules or circles of various sizes were frequently found that continued with the filamentous structures. In addition, a more brightly stained structure, possibly Mf organizing center, was observed. Treatment of pollen tubes with cytochalasin D(CD)for increasing time intervals (5-40 minutes) caused gradual reduction of strands until flurescent granules filled up the pollen tubes. Mcanwhile, cytoplasmie streaming was inhibited completely. Though closely associated with vegetative nuclei (VN) and generative cells (GC), AFs were not found in the cytoplasm of GC.Mg++concentration greatly affected the isolated Mfs.
基金supported by the Key Projects of the Joint Fund of the National Natural Science Foundation of China(U1802232 to H.S.)the Second Tibetan Plateau Scientific Expedition and Research(STEP)programme(2019QZKK0502)+2 种基金Ministry of Science and Technology of the People’s Republic of China,National Natural Science Foundation of China(31670214 to Y.N.)the Youth Innovation Promotion Association,Chinese Academy of Sciences(2018427 to Y.N.)Yunnan Ten Thousand Talents Plan Young&Elite Talents Project,Science&Technology Department of Yunnan Province.
文摘Aims Bee-pollinated flowers are rarely red,presumably because bees(which lack red receptors)have difficulty detecting red targets.Although the response of bees to red colour has been investigated in lab experiments,most stimuli have been pure red,while the subtle diversity of red as perceived by humans(human-red)has received very limited attention.Here we test the hypothesis that ultraviolet(UV)reflected from human-red flowers enhances their attractiveness to bees,through increased chromatic contrast.Methods Using Onosma confertum(Boraginaceae),a plant with UV-reflecting red flowers that are pollinated by bumblebees,we investigated the effects of UV reflection on pollinator responses by conducting phenotypic manipulation experiments in the field.Colour preferences of flower-naïve bumblebees were also examined.Colour perception by bumblebees was estimated in terms of chromatic and achromatic contrast,based on two different colour perception models.Important Findings We found that both natural and flower-naïve bumblebees strongly preferred visiting UV-reflecting targets compared with UV-absorbing ones.Colour models show that the UV-reflecting flowers exhibit higher spectral purity and higher chromatic contrast against the foliage background,whereas they have similar achromatic contrast in terms of green receptor contrast.These results indicate that the component of UV reflection increases chromatic contrast in O.confertum,enhancing the visual attractiveness of these red flowers to bumblebees.We further infer that the secondary reflectance might be a necessary component in human-red flowers that are primarily pollinated by animals without red receptors,such as bees.
