环境因子对蕨类植物孢子萌发的影响

蕨类植物通过孢子萌发形成独立生活的配子体,配子体能够形成精子器和颈卵器,进而通过受精作用形成新的孢子体。孢子萌发是蕨类植物生活史过程中配子体世代向孢子体世代转变的关键步骤。同时,此过程不仅受到多种环境因子的影响,也是研究细胞核极性移动、细胞不对称分裂、假根极性生长等独特的细胞学事件的良好模型。迄今为止,人们已经研究发现多种环境因子对约200余种蕨类植物孢子萌发有影响。总结了环境因子对蕨类植物孢子萌发影响的规律如下:(1)孢子萌发除了受到光照强度影响外,主要受光质的影响,光质的影响主要表现为4种方式:①孢子萌发受红光刺激与远红光抑制像开关一样调控;②孢子萌发不受远红光抑制;③孢子萌发受蓝光抑制;④孢子只能在黑暗条件下萌发。(2)重力作用会影响孢子细胞核移动,进而影响孢子细胞发育的极性。(3)赤霉素(GA)能增加孢子萌发率或帮助孢子打破休眠。成精子囊素与GA作用相似,启动或促进孢子萌发。而脱落酸(ABA)、茉莉酸(JA)和乙烯等其它激素对孢子萌发的影响相对较小。(4)不同植物孢子有着各自最适的萌发培养基条件,如不同种类孢子对MS培养基中无机盐含量、蔗糖含量、pH值的要求不同。孢子外被中的Ca2+、Mn2+和Mg2+,培养基中的Cd2+和La3+,以及孢子接种密度、萌发空间CO2含量也会对孢子萌发造成影响。(5)多数蕨类植物孢子在15-30℃可以萌发,最适萌发温度为25℃。(6)4℃和液氮储藏可以延长孢子寿命并保持较高萌发率。     

Photocontrol of spore germination in the fern Thelypteris kunthii

The light requirement for germination in spores of the fern Thelypteris kunthii (Desv.) Morton was fully satisfied by a long period of continuous red light or partially by intermittent, short periods of red light. Red light-potentiated spore germination was inhibited by brief far-red light irradiation, indicating phytochrome involvement. Repeated exposure of spores to prolonged red and short far-red irradiations, or exposure of red-potentiated spores to far-red light after an extended period in darkness, led to their escape from inhibition of germination by far-red light. Prolonged irradiation of spores with blue light before or after red light treatment partially antagonized the effect of red light.     

Light dependent spore germination in Woodwardia radicans (L.) Sm

Abstract

The spores of Woodwardia radicans can germinate indifferently either in water or in culture media containing mineral salts at temperatures (15-24°C) falling within a range believed optimal for many other ferns (15-30 C).

The spores are photosensitive, will not germinate in the dark and the addition of gibberellic acid is ineffective in substituting a light requirement. Spore germination was induced by white and red light and phytochrome seems to be implicated in the control of germination since far-red light (and not the blue irradiation) can reverse the stimulating effect of the red light.

Spore morphology and spore germination pattern was studied using light and scanning electron microscopes.

It was concluded that the progressive disappearance of W. radicans from the Italian localities is not due to difficulties in spore germination but is related to problems that arise during the subsequent stages.     

Arsenic-resistant proteobacterium from the phyllosphere of arsenic-hyperaccumulating fern (Pteris vittata L.) reduces arsenate to arsenite

An arsenic-resistant bacterium, AsRB1, was isolated from the fronds of Pteris vittata grown in a site contaminated with copper chromium arsenate. The bacterium exhibited resistance to arsenate, arsenite, and antimony in the culture medium. AsRB1, like Pseudomonas putida, grew on MacConkey and xylose-lactose-desoxycholate agars and utilized citrate but, unlike P. putida, was positive for indole test and negative for oxidase test. A phylogenetic analysis of the 16S rRNA gene showed that AsRB1 is a proteobacterium of the beta subclass, related to Pseudomonas saccharophila and Variovorax paradoxus. Following an exogenous supply of arsenate, most arsenic occurred as arsenite in the medium and the cell extracts, suggesting reduction and extrusion of arsenic as the mechanism for arsenic resistance in AsRB1.     

The effects of methyl jasmonate on sunflower (Helianthus annuus L.) seed germination and seedling development

Some effects of methyl jasmonate (Me-Ja) on sunflower (Helianthus annuus L.) seed germination and seedling development are described and compared with those of ABA. Both growth regulators have very similar action. They inhibit germination, but high concentrations of O₂ in the atmosphere suppress this inhibitory action. Depending on the concentration, Me-Ja inhibits root and hypcotyl growth, however the root is more sensitive to Me-Ja than to ABA. Me-Ja also strongly reduces oxygen uptake during germination and inhibits chlorophyll biosynthesis in isolated cotyledons.     

Leaf development of the ostrich fern Matteuccia struthiopteris (L.) Todaro

The timing of emergence of the three different leaf types of Matteuccia struthiopteris is described from plants sampled over the course of a growing season. Vegetative leaves were first to appear, followed five weeks later by sporophylls and cataphylls. Leaf number and type, and total leaf dry weight per plant were assessed in weekly transects. Vegetative fronds contributed the most to total leaf dry weight, which increased during the first four weeks, and then remained constant for the remainder of the season. Cataphylls, although numerous by the end of the season, contributed little weight. Sporophylls occurred on the widest plants with the most vegetative leaves and greatest leaf weight, whereas cataphylls occurred on most plants except the smallest. Experimentally defoliated plants were re-examined in late summer. Following initial harvest, plants often produced a second smaller set of leaves. These were restricted to vegetative leaves and cataphylls. Ability to reissue leaves, especially vegetative fronds, declined very quickly after the first few weeks in the growing season. Defoliated plants draw on the extensive reservoir of developing leaves which are found on the rhizome, thus possibly diminishing the ability of the plant to withstand regular harvesting of the young fronds for food. Individual leaves were tagged and measured over the growing season. Non-linear regression curves fitted to the growth data for the three types of leaves indicate that growth was described best by a monomolecular growth curve for the vegetative and fertile fronds. Cataphyllar growth could be described equally well by either a monomolecular or a logistic function.     

Leaf development of the ostrich fern Matteuccia struthiopteris (L.) Todaro

The timing of emergence of the three different leaf types of Matteuccia struthiopteris is described from plants sampled over the course of a growing season. Vegetative leaves were first to appear, followed five weeks later by sporophylls and cataphylls. Leaf number and type, and total leaf dry weight per plant were assessed in weekly transects. Vegetative fronds contributed the most to total leaf dry weight, which increased during the first four weeks, and then remained constant for the remainder of the season. Cataphylls, although numerous by the end of the season, contributed little weight. Sporophylls occurred on the widest plants with the most vegetative leaves and greatest leaf weight, whereas cataphylls occurred on most plants except the smallest. Experimentally defoliated plants were re-examined in late summer. Following initial harvest, plants often produced a second smaller set of leaves. These were restricted to vegetative leaves and cataphylls. Ability to reissue leaves, especially vegetative fronds, declined very quickly after the first few weeks in the growing season. Defoliated plants draw on the extensive reservoir of developing leaves which are found on the rhizome, thus possibly diminishing the ability of the plant to withstand regular harvesting of the young fronds for food. Individual leaves were tagged and measured over the growing season. Non-linear regression curves fitted to the growth data for the three types of leaves indicate that growth was described best by a monomolecular growth curve for the vegetative and fertile fronds. Cataphyllar growth could be described equally well by either a monomolecular or a logistic function.     

The effect of leaf exudates on the spore germination of phylloplane mycoflora of chilli (Capsicum annuum L.) cultivars

Summary Ninetten aminoacids, twelve sugars, eleven organic acids and ten phenols were detected in the leaf exudates of three cultivars of chilli. The number of aminoacids, sugars, organic acids and phenols increased as the plants grew older. More aminoacids and sugars were detected in the exudate from the susceptible cultivar (Malwa). More organic acids and phenols were detected from the resistant cultivar (Simla). The leaf exudate of the resistant cultivar (Simla) inhibited spore germination of the pathogen (Alternaria solani) while that of susceptible (Malwa) stimulated spore germination. The cultivar ‘Patna’ which is moderately resistant, occupied an intermediate position. Spore germination of the isolated fungi was enhanced in leaf exudate of susceptible cultivar (Malwa), while leaf exudates of the moderately resistant (Patna) and resistant (Simla) inhibited spore germination of the majority of fungi isolated. Most of the antagonistic fungi were not isolated from the susceptible cultivar and the percentage spore germination of these fungi was less in leaf exudate of the susceptible cultivar, while leaf exudates of resistant cultivars enhanced the percentage spore germination of antagonistic fungi,viz Aspergillus flavus, A. fumigatus, A. versicolor, Penicillium citrinum, P. restrictum andTrichoderma viride.     

Relationship between fern development and CAM in Pyrrosia piloselloides (L.) Price

Pyrrosia piloselloides (L.) Price is a constitutive CAM plant in the sporophytic phase of its life-cycle. Newly developed sporophytes, still attached to the gametophytes, showed signs of CAM expression in terms of diurnal changes in titratable acidity of the tissues. The gametophytes did not exhibit CAM. This revised version was published online in June 2006 with corrections to the Cover Date.     

Relationship between fern development and CAM in Pyrrosia piloselloides (L.) Price

Pyrrosia piloselloides (L.) Price is a constitutive CAM plant in the sporophytic phase of its life-cycle. Newly developed sporophytes, still attached to the gametophytes, showed signs of CAM expression in terms of diurnal changes in titratable acidity of the tissues. The gametophytes did not exhibit CAM.     

Notes on the Effect of Cutting Bracken (Pteris aquilina L.)

Background: Undisturbed high elevation treelines follow a common growing season isotherm, irrespective of latitude. Small stature plants thrive at much higher elevations because they grow in a favourable microclimate near the ground, whereas trees are aerodynamically coupled to free atmospheric circulation, hence the uniform treeline elevation in a given region.

Aims: I argue that the treeline results from tree architecture and not from a tree-specific inferior physiology. At tissue level, all cold adapted higher plants (including winter crops) face similar temperature related limitations and are constrained by similar thermal thresholds.

Methods: In order to explore this hypothesis, winter rape and winter oat were grown in the field and the daily rate of leaf expansion was measured during early winter, with temperatures similar to those at treeline at the beginning of the growing season (monthly mean temperature of 5 °C).

Results: Leaves of these winter crops only grew when the degree hours above 5 °C for a given day exceeded zero. Rape and oats showed very similar responses. The data support a common temperature threshold for tissue formation in winter crops and treeline trees.

Conclusions: A literature survey revealed lower temperature thresholds (close to freezing point) in arctic and Antarctic algae. It appears that the formation of complex, partly lignified tissue does not happen below 5 °C, whereas such temperatures exert little constraints on photosynthesis. The study illustrates that tissue growth in winter crops can help understand growth of treeline trees, given that both exhibit similar minimum temperature requirements for meristem functioning.     

Phytoremediation of arsenic-contaminated groundwater by the arsenic hyperaccumulating fern Pteris vittata L

Arsenic concentrations in a much larger fraction of U.S. groundwater sources will exceed the maximum contaminant limit when the new 10 microg L(-1) EPA standard for drinking water takes effect in 2006. Thus, it is important to develop remediation technologies that can meet this new standard. Phytoremediation of arsenic-contaminated groundwater is a relatively new idea. In this research, an arsenic-hyperaccumulating fern, commonly known as Chinese Brake fern (Pteris vittata L.), was grown hydroponically to examine its effectiveness in arsenic removal from what is believed to be herbicide-contaminated groundwater. One plant grown in 600 mL of groundwater effectively reduced the arsenic concentration from 46 to less than 10 microg L(-1) in 3 days. Re-used plants continued to take up arsenic from the groundwater, albeit at a slower rate (from 46 to 20 microg L(-1) during the same time). Young fern plants were more efficient in removing arsenic than were older fern plants of similar size. The addition of a supplement of phosphate-free Hoagland nutrition to the groundwater had little effect on arsenic removal, but the addition of phosphate nutrition significantly reduced its arsenic affinity and, thus, inhibited the arsenic removal. This study suggested that Chinese Brake has some potential to remove arsenic from groundwater.     

Molecular phylogeny and biogeography of the fern genus Pteris (Pteridaceae)

Background and Aims

Pteris (Pteridaceae), comprising over 250 species, had been thought to be a monophyletic genus until the three monotypic genera Neurocallis, Ochropteris and Platyzoma were included. However, the relationships between the type species of the genus Pteris, P. longifolia, and other species are still unknown. Furthermore, several infrageneric morphological classifications have been proposed, but are debated. To date, no worldwide phylogenetic hypothesis has been proposed for the genus, and no comprehensive biogeographical history of Pteris, crucial to understanding its cosmopolitan distribution, has been presented.

Methods

A molecular phylogeny of Pteris is presented for 135 species, based on cpDNA rbcL and matK and using maximum parsimony, maximum likelihood and Bayesian inference approaches. The inferred phylogeny was used to assess the biogeographical history of Pteris and to reconstruct the evolution of one ecological and four morphological characters commonly used for infrageneric classifications.

Key Results

The monophyly of Pteris remains uncertain, especially regarding the relationship of Pteris with Actiniopteris + Onychium and Platyzoma. Pteris comprises 11 clades supported by combinations of ecological and morphological character states, but none of the characters used in previous classifications were found to be exclusive synapomorphies. The results indicate that Pteris diversified around 47 million years ago, and when species colonized new geographical areas they generated new lineages, which are associated with morphological character transitions.

Conclusions

This first phylogeny of Pteris on a global scale and including more than half of the diversity of the genus should contribute to a new, more reliable infrageneric classification of Pteris, based not only on a few morphological characters but also on ecological traits and geographical distribution. The inferred biogeographical history highlights long-distance dispersal as a major process shaping the worldwide distribution of the species. Colonization of different niches was followed by subsequent morphological diversification. Dispersal events followed by allopatric and parapatric speciation contribute to the species diversity of Pteris.     

Lipid and oxylipin profiles during aging and sprout development in potato tubers (Solanum tuberosum L.)

Potato tubers (Solanum tuberosum L. cv Bintje) were stored at 20 degrees C for 210 days without desprouting to study the lipoxygenase pathway during aging. After 15 days of storage, potato tubers sprouted, while after 45-60 days, apical dominance was lost and multiple sprouts developed. Analysis of the fatty acid hydroperoxides (HPOs) revealed that 9-S-hydroperoxide of linoleic acid (9-HPOD) was the main oxylipin formed. Between 45 and 60 days of storage, increases in the levels of 9-HPOD and colneleic acid were observed. Analysis of phospholipids and galactolipids by electrospray ionisation tandem mass spectrometry (ESI-MS/MS) showed that a decrease in the levels of phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol (PI), digalactosyldiacylglycerol (DGDG), and monogalactosyldiacylglycerol (MGDG) occurred between 0 and 45 days of aging. The decrease in the amount of linoleic acid in complex lipids correlates well with the amount of 9-HPOD and colneleic acid produced.     

Hormonal regulation of germination and early seedling development in Acer pseudoplatanus (L.)

Summary Dormancy of intact sycamore (Acer pseudoplatanus) seeds was broken by chilling (5°C) for several weeks in moist conditions. Treatment of unchilled seeds with kinetin induced some germination, but gibberellin was ineffective. This stimulation by kinetin was not suppressed by the added presence of abscisic acid during incubation.The chilling requirement of intact seeds was eliminated by removal of the testa, and the naked embryos developed with no morphological abnormalities. During early growth of isolated embryos in the light, two distinct developmental processes were recognised. One involved initial elongation of the radicle accompanied by geotropic curvature and was stimulated by kinetin but not by gibberellin, while the other involved unrolling of the cotyledons, which was accelerated by gibberellin but much less by kinetin. Abscisic acid strongly suppressed both developmental processes when applied alone, inhibited cotyledon expansion in the presence of gibberellin, but failed to overcome the promotory effects of kinetin on radicle growth. Experiments with CCC indicated that under natural conditions the unrolling of the cotyledons is dependent upon endogenous gibberellin. Radicle growth of isolated embryos was unimpaired by incubation in the dark, but cotyledon expansion of water incubated embryos was poor, and although it was accelerated by gibberellin, the responses in all treatments were slower than in the corresponding light grown samples.It is suggested that endogenous cytokinins are primary factors in the initiation of radicle growth, while gibberellins are important in cotyledon expansion. Abscisic acid appears to have an inhibitory role in both processes, and the interactions of these regulators in the control of germination and development are discussed.     

山黧豆(Lathyrus sativus L.)苗菜用品种的筛选与评价

针对山黧豆苗菜用特性评价体系不完善和优良品种鉴别不明确的现状,收集我国不同地区的29份山黧豆品种资源作为供试材料,模拟中农绿谷芽苗菜研究院山黧豆苗的培育工艺与条件,根据山黧豆及山黧豆苗的8项性状指标,采用基本统计量分析、K-均值聚类分析和相关性分析对山黧豆苗菜用特性进行初步评价。结果表明,各性状中苗菜产出量的变异最大,变异系数为24.42%。29份山黧豆品种资源可划分为5个类群。其中一类具有小粒、高苗菜产出量、高可溶性蛋白含量、高VC含量的特征。苗长与苗菜产出量和种皮的光滑程度极显著正相关;苗菜产出量与品种种皮光滑程度极显著正相关,与百粒重显著负相关。本研究显示,鉴定与评价山黧豆品种苗菜用特性优劣时,应重点考虑苗菜产出量并兼顾营养品质和感官品质,优先筛选苗菜产出量≥1.01的品种作为芽用备选资源。初步筛选出甘肃张掖山黧豆、白香山黧豆、阿杂山黧豆-2共3份优异资源,供进一步研究。