Pollen production,microsporangium dehiscence and pollen flow in Himalayan cedar (Cedrus deodara Roxb. ex d. Don)

Microsporangium dehiscence, pollen production and dispersal were studied in Himalayan cedar (Cedrus deodara) during 1998 and 1999. Microsporangium dehiscence showed diurnal periodicity and was found to be related to air temperature and relative air humidity, with a strobilus taking 2 d to dehisce completely in warmer conditions and 3 d in cooler ones. The frequency of flowering in C. deodara was highly variable during the two successive years; however, cyclical production of pollen grains was observed in 50% of the trees. The maximum concentration of pollen grains in the air was found between 1200 and 1600 h, and this period was also noted to be the best time for pollination. Studying migration of pollen grains from isolated single trees in three directions showed that migration was not uniform in all directions. Long-distance transport of pollen grains was observed in the downhill direction. However, in the uphill and horizontal directions grains could travel only up to 97.5 and l95.1 m, respectively, and the frequency of pollen grains to the source frequency at these distances was only 1.9 and 2-5%, respectively. The results suggest that an isolation barrier of 190 m may be considered as a minimum for the management of deodar seed orchards.     

陕西中部黄土高原地区空气花粉组成及其与气候因子的关系——以洛川县下黑木沟村为例

空气花粉研究是现代孢粉学、植被变迁与预测的重要内容之一.陕西省黄土高原地区洛川县2007-2009连续2a的空气花粉分析表明:空气花粉组成与区域植被分布特征和植物花期一致.与2007—2008年相比,2008-2009年的花粉总通量及蒿属花粉通量明显增加,但木本植物花粉通量降低,这主要与2008-2009年降水明显偏少密切相关.2007-2008年降雨量高于500 mm,花粉组合中乔木花粉百分比高于30％,表现出森林植被特点;2008-2009年降雨量少于450 mm,花粉组合中草本花粉高于80％,乔木花粉低于10％,更多表现出草原植被特点.但从植被观测来看并没有明显的变化,表明花粉组合较植被对气候变化更为敏感.主要花粉类型与气候因子的相关分析表明:气候因子影响空气花粉的组成及数量.栎属、松属、蔷薇科花粉数量主要受春季温度影响,温度越高花粉数量越多;其他季节花粉数量主要受相对湿度影响,湿度越低,花粉数量越大.榆属花粉数量主要与冬季温度有关,温度越高,花粉数量越高.杨属只受春季温度影响,春季温度越低,花粉数量越多.胡颓子科花粉含量主要受春季相对湿度、风速影响,相对湿度越低,风速越大,花粉数量越多.绝大多数草本花粉数量均主要受春、冬季相对湿度及风速影响,相对湿度越低,风速越大,花粉数量越高;此外,禾本科花粉数量还受春季温度影响,温度越高,花粉数量越多;菊科花粉数量在夏秋季节还受温度、湿度和风速的共同影响,温度越低,湿度越低,风速越大,花粉数量越多.这些结果表明,黄土高原中部地区的空气花粉特征能反映区域植被组成,且对气候变化非常敏感,对认识和预测当地气候变化与植被动态等具有重要意义.     

Pollination Ecophysiology of Mercurialis annua L. (Euphorbiaceae), an Anemophilous Species Flowering all Year Round

Mercurialis annua L. is a dioecious anemophilous species thatflowers all year round in central and southern Italy. The flowersof both sexes are dimorphic: the female flower has a vestigialcalyx; the male flower consists only of a calyx that opens atanthesis. The anthers always dehisce after anthesis. The anthesisof male flowers seems to be temperature dependent, whereas antherdehiscence is related to relative humidity. The pollen grainsvary in volume according to the season: they are smaller whenrelative humidity is low and vice versa. They always decreasein volume after anther dehiscence and have the capacity to varyin volume and reach equilibrium with a changing environment.Viability is high, but may drop suddenly during heavy rain orhail that damage the exposed male flowers. The number of pollengrains per stigma varies from 0 to 300. The data is discussedin relation to the type of pollination and environmental characteristics.Copyright1994, 1999 Academic Press Mercurialis annua, dioecism, anthesis, anther dehiscence, pollen volume, pollen viability, anemophilous pollination, pollination ecology     

Effects of relative humidity and temperature stress on pollen viability of Cistus incanus and Myrtus communis

Cistus incanus and Myrtus communis are two species commonly found in Mediterranean shrublands, flowering respectively in spring and summer. Pollen of single flowers of C. incanus is available for dispersal for 8-10 hours, during which time viability decreases from 91% to 61%. Field measurements of the variation in the percent pollen viability during the anthesis of single flowers of M. communis shows that, immediately after anthesis, pollen viability is very high; by the end of the first day it significantly declines and 36 hours after anthesis almost all grains are unviable. Experiments carried out under controlled environment showed that, in C. incanus, the greatest loss of viability occurs at 100% humidity and high temperatures, while under dry conditions pollen viability remains high throughout a wide temperature range. Similarly, pollen viability of M. communis remains high for several hours at high temperature and dry conditions, while it rapidly decreases at high humidity. In conclusion, the temperature experiments indicate that in C. incanus and M. communis, pollen viability does not appear to be drastically reduced if the relative humidity of the environment is low. Therefore, humidity is a far more important factor determining pollen viability loss in both species.     

小叶榕气生根气体交换特征及影响因子研究

用LI-6400XT便携式光合仪测定了小叶榕(Ficus microcarpa L. f.)气生根的气体交换特征。结果表明气生根具有呼吸、蒸腾作用和空气吸湿作用。影响气生根呼吸作用的因素为年龄>空气温度>光强>相对湿度;影响蒸腾作用的因素为年龄>相对湿度>空气温度>光照。年龄小的气生根的呼吸和蒸腾作用较强,年龄大的尤其是木质化程度较高的气生根的呼吸作用较小,水分的释放(蒸腾作用)转变为水分的吸收(吸湿作用)。年龄小的气生根的CO2交换率与温度呈线性关系,温度越高,CO2交换率越大,呼吸越强;H2O交换率与相对湿度呈线性关系,相对湿度越大,H2O交换率越小,蒸腾越弱;年龄大的成熟气生根的H2O交换率与空气相对湿度呈线性关系,相对湿度越大,H2O交换率越小,蒸腾越小。     

生态因子对滇重楼花药开裂的影响

滇重楼为延龄草科重楼属植物,具有极高的药用价值,由于重楼传统药用部位生长缓慢、繁殖力低下,以及人们对野生重楼资源的过度采挖使其资源日趋枯竭。滇重楼的花药在整个花期中存在开裂－关闭的现象,花药的有效闭合应是保护花粉、延长花粉寿命、增强雄性适合度的一种适应机制。该研究以滇重楼为对象,通过设计正交实验和对比实验,观测其花药开裂过程中的光照强度、温度、湿度的变化,探究光照强度、温度、湿度等生态因子对滇重楼花药开裂的影响以及滇重楼花药开裂与生态因子变化的关系。结果表明：(1)在滇重楼花药开裂的过程中,光照强度增强、温度升高、相对湿度下降;(2)温度是影响滇重楼花药开裂时间的主导因子,升温促进花药开裂,降温促进花药关闭;(3)高湿度及黑暗推迟花药开裂,但并不能阻止花药开裂;(4)低温可使滇重楼花药持续关闭,而光照强度越高,花药持续关闭所需的温度越低。该研究有利于解释滇重楼花药白天开裂夜晚关闭的现象与环境因子的关系,对滇重楼的栽培育种提供理论指导。     

The Effect of Meteorological Conditions on Anthesis in Agricultural Grasses

The effects of air temperature, relative air humidity, lightintensity, and wind were investigated on plants in pots, includingAlopecurus, Dactylis, Festuca, Lolium, and Phleum. Anthesiswas positively related to temperature and light, by which itwas activated. These factors did not seem to reach above optimalvalues under the conditions of the experiment, i.e. daily averagetemperature not exceeding 20? C. and daily average light intensitynot exceeding 2, 800 ft.-c. Under these conditions wind hinderedanthesis and became inhibitory between 13–19 km.p.h. Relativeair humidity did not have a significant direct effect, but itcasually inhibited anthesis through reducing light intensity,or through precipitation. Environmental effects may exceed varietaldifferences; the latter were also significant and seem to beof genetical origin. It is suggested that grasses be grouped according to the velocityof their physiological responses to environmental effects, andthat the groups may be called ‘quick-staminating’and ‘show-staminating’. Additional characteristicsare described to promote this distinction between the groups.It is noted that factors which are operative in anthesis alsoaffect plant temperatures in the same way. The possible applicationof the results are discussed.     

The effects of abiotic factors on induced volatile emissions in corn plants

Many plants respond to herbivory by releasing a specific blend of volatiles that is attractive to natural enemies of the herbivores. In corn (Zea mays), this induced odor blend is mainly composed of terpenoids and indole. The induced signal varies with plant species and genotype, but little is known about the variation due to abiotic factors. Here, we tested the effect of soil humidity, air humidity, temperature, light, and fertilization rate on the emission of induced volatiles in young corn plants. Each factor was tested separately under constant conditions for the other factors. Plants released more when standing in dry soil than in wet soil, whereas for air humidity, the optimal release was found at around 60% relative humidity. Temperatures between 22 degrees C and 27 degrees C led to a higher emission than lower or higher temperatures. Light intensity had a dramatic effect. The emission of volatiles did not occur in the dark and increased steadily with an increase in the light intensity. An experiment with an unnatural light-dark cycle showed that the release was fully photophase dependent. Fertilization also had a strong positive effect; the emission of volatiles was minimal when plants were grown under low nutrition, even when results were corrected for plant biomass. Changes in all abiotic factors caused small but significant changes in the relative ratios among the different compounds (quality) in the induced odor blends, except for air humidity. Hence, climatic conditions and nutrient availability can be important factors in determining the intensity and variability in the release of induced plant volatiles.     

广西岩溶植被演替过程中主要小气候因子日变化特征

选择广西不同气候带下具有典型性和代表性的岩溶区作为研究区域,调查和监测了岩溶植被演替过程中主要小气候因子的日变化特征。结果表明,在石荒漠阶段和草丛阶段,群落光照强、土温和气温高、空气相对湿度低,时间波动比较明显:灌丛阶段群落冠层以下的照度、气温均较低,随时间变化的幅度不大,而冠层以上的光照强度和气温均出现了大幅上升,而且随时间变化的幅度较大;落叶阔叶林阶段和常绿落叶阔叶混交林阶段群落内部的照度、气温及土壤温度均大幅降低,空气相对湿度保持在较大水平,主要小气候因子的时空变化比较平缓。主要小气候因子的时空动态与群落结构和群落种类组成特征密切相关。     

The flower biology of Daphne gnidium L. (Thymelaeaceae)

Daphne gnidium is a circum-Mediterranean evergreen shrub. Flower and pollen features related to pollination mechanism were analyzed, and the seasonal presence of insects visiting the plant was monitored. The morphology and functionality of flowers are compatible with entomophily, as are pollen viability, which is maintained for a few hours only after anthesis, and the very short stigmatic receptivity. The reproductive fitness of the species is low and the ripening process often fails (35% collapsed embryos). While male organ functionality is fairly regular, the female organ often shows developmental arrest. The complex or transient evolutionary traits displayed by D. gnidium are comparable to those of Thymelaea hirsuta and other members of the Thymelaeaceae.     

Anther opening, pollen biology and stigma receptivity in the long blooming species, Parietaria judaica L. (Urticaceae)

Background and aimsThis paper is about pollen ecophysiology, anther opening, pollen dispersal and the timing of the male and female phases in Parietaria judaica (Urticaceae).MethodsEcophysiological (effects of different relative humidities (RHs) and osmotic relationships) and cytological methods (stigmatic receptivity, pollen viability, histology and histochemistry) were used to determine pollen and pollination features during the long blooming period of this species.Key resultsPollen is dispersed by rapid uncurling of the filament and anther opening. The filament and anther lack cells with lignified wall thickenings, which are usually responsible for anther opening and ballistic pollen dispersal. Instead, dispersal is the result of the sudden movement of the filament. Pollen is of the partially hydrated type, i.e. with a water content greater than 30% at shedding, and readily loses water, and hence viability, at low RH. Pollen carbohydrate reserves differ with season. Starchless grains germinate quickly and are less subject to water loss. Flowers are protogynous, pollen release occurring only after complete cessation of the female phase within an inflorescence.ConclusionParietaria has partially hydrated pollen which differs from typical pollen of this type because of its reduced size and the absence of callose. Because of its low water content at the time of shedding it survives better at higher RH. Dispersal and pollination are adapted to pollen features.     

软质与硬质地表对树木花粉日飘散变化的影响

以油松(Pinus tabulaeformis)、白玉兰(Magnolia denudata)、白皮松(Pinus bungeana)、臭椿(Ailanthus altissima)为被试树种,对比研究了春季静风晴朗天气中软质与硬质两种地表条件下不同树种在距树10m高度1.5m处花粉浓度的日变化特征。研究结果表明:(1)4个树种在相同地表环境的花粉浓度日变化趋势基本一致,但同一树种花粉浓度的日变化特征在软、硬两种地表条件下的差异明显。软质地面一天内空气中花粉浓度最大值出现14:00时前后,04:00时花粉浓度最低,这与全天内空气温度的变化正好一致,而与空气相对湿度的变化恰好相反。硬质地表近地空间空气中的花粉浓度则呈现"双峰型"日变化特征,两次峰值分别出现在14:00时和20:00时,硬质地面花粉浓度20:00时晚高峰的出现时间与硬质地面温度日峰值一致。(2)分析硬质地表20:00时花粉浓度高峰出现的原因可能与硬质地面的散热特性有关,硬质地面夜间释放积蓄热量的过程会在一定程度上增强近地面空气的对流运动,并辅助空气中的花粉粒子不断飘散,形成花粉浓度晚高峰。(3)相对于软质地面来讲,硬质地表对空气中花粉飘散的影响作用持续时间更长,这也在一定程度上延长了致敏花粉的危害时间,加剧了致敏花粉的污染程度。研究还进一步在花粉致敏树种栽植、地表覆盖方式等方面进行了讨论;同时建议花粉症患者根据花粉污染发生规律合理规避花粉浓度聚集高峰期出行,从而有效缓解致敏花粉对易感人群的健康威胁。     

Società Botanica Italiana Congresso Sociale 1982 Parto—12-14 Ottobre Relazioni

Abstract

« Harmomegathy »: a still open problem not yet well-known. - Wodehouse used the term « Harmomegathy » to indicate the form and volume change in pollen grains, due to water loss or assumption. Roundish and tricolporate grains in the anther become oval and decrease in volume during the dehydration preceeding anthesis. Viceversa during rehydration on the stigma they undergo the opposite process.

Pollen water content at an thesis varies from species to species and it usually ranges between 10 and 20%; nevertheless in some families as Zingiberaceae and Araceae it is higher. Anther and pollen dehydrations are affected by environmental factors, such as humidity of air and temperature, before the anthesis and when pollen is suspended in air. Besides, to avoid the further loss of water during pollen flow, an oily layer derived from tapetum degeneration is deposited outside the pollen grains.

During dehydration and rehydration pollen grains undergo a stress due to shape and volume changes expecially in the colpus and/or pore areas. Pollen walls are structured in order to avoid their own damage, which could be followed by protoplast death and/or irregularities in grain shape. Intine, formed by pectocellulosic filaments, has elastic properties, as sporopollenin, the component of exine.

Stigma can be dry or wet, namely covered or not by stigmatic exudate giving place to different hydration patterns. The structure of intine and exine has to match that of the stigma, in fact pollen will find the best place and way to proper hydration only on stigmas of its own species. Grains structure also must be sterically conform to stigma: this is well-shown in species as Linum, Lytrum and Primula which have an heteromorphic autoincompatibility.

The right keeping of shape and structure of grains, despite the hydration and dehydration, is therefore essential to the physical-morphological recognition between pollen and stigma, which preceedes the biochemical recognition.     

Airborne behaviour of <Emphasis Type="Italic">Echium</Emphasis> pollen

Species of Echium are clearly entomophilous, but they release great amounts of pollen into the atmosphere with its consequent anemophilous transport, because their high pollen production, the smallness of the grains, and the exserted position of their anthers. Using three volumetric airborne sporetraps in Extremadura (SW of Spain) between 1994 and 1998, we found that Echium pollen reached pollen concentrations similar to or greater than other anemophilous plants. The main pollination period appeared from April to June. The maximum peak daily concentration reached 35.9 grains/m³ and the annual recorded totals showed interannual variations between 64.2 and 614.4. Correlations were calculated between the daily pollen concentrations and the meteorological parameters rain, temperature, wind direction and velocity and relative humidity. Wind direction seems to be significant, warm dry air seems to facilitate the release of pollen into the atmosphere and increase its concentrations. Hourly pollen concentration reached a maximum between 11:00 and 12:00 and a minimum at 07:00, and the patterns were very similar in the three localities studied. This would indicate that the presence of Echium pollen in the atmosphere is related to the processes of anthesis of the populations near the traps, and would not correspond to a model of transport from distant zones.     

Effects of relative humidity and temperature conditions on pollen fluorochromatic reaction of Rosmarinus officinalis L. (Lamiaceae)

Summary. Mediterranean ecosystems are characterized by seasonal and annual fluctuations in humidity and temperature which are considered limiting factors for plant growth and might have played a key role in the selection of species that compose the present vegetation. After anther release, pollen is generally exposed to various changes of temperature and humidity conditions, therefore its viability and consequently successful fruit set are strongly affected by these environmental parameters. The aim of this research was to study the effect of different combinations of humidity and temperature on pollen membrane integrity of Rosmarinus officinalis L. in order to investigate possible relations between pollen features and climatic conditions during flowering. This species is an evergreen perennial shrub, occurring among the sclerophyllous vegetation of Mediterranean maquis. In many areas of Southern Italy, it shows a flowering period starting from the beginning of winter and spreading throughout spring months. The analysis of data showed that duration of pollen viability of R. officinalis is enhanced by the co-occurrence of low temperature and high humidity. Moreover, these conditions are able to newly raise the viability of pollen kept at higher temperatures and lower humidity. These observations indicate that reactivation of the pollen membrane depends on low temperature apart from high humidity. Therefore “vernalization” of rosemary pollen enhances its viability, supporting that pollen behavior is adapted to winter condition and allows flowering in winter and early spring. Correspondence and reprints: Laboratorio di Botanica ed Ecologia Riproduttiva, Dipartimento di Arboricoltura, Botanica e Patologia Vegetale, Università degli Studi di Napoli Federico II, Via Università 100, 80055 Portici, Naples, Italy.     

气候变化对中国东北地区日本松干蚧传播扩散的影响

基于气候资料和日本松干蚧传播资料,根据传播扩散范围及入侵地的气候特征,分析了日本松干蚧主要影响因子的年代变化对日本松干蚧在东北地区扩散的影响。结果表明:东北地区最冷月各旬及月平均最低气温总的呈升高趋势(r=0.86,P0.05),冬季极端最低气温也有缓慢上升趋势(r=0.93,P0.01),其年代间的冷暖变化与日本松干蚧在东北地区扩散有明显的相关性。1月平均最低气温和冬季极端最低气温明显升高的20世纪70年代和90年代,日本松干蚧快速扩散、危害地虫口密度大、危害程度重。日本松干蚧大范围扩散和爆发都发生在1月份最低气温较高的年份。1月最低气温和冬季极端最低气温升高是日本松干蚧在东北地区传播扩散的重要因素。复苏后的降水量、卵孵化期的空气相对湿度和夏季最高气温的年代变化对日本松干蚧扩散的影响不显著。     

Effect of canopy closure on pollen dispersal in a wind-pollinated species (Fagus sylvatica L.)

The effect of non-reproductive trees and saplings as a physical barrier to pollen dispersal in wind-pollinated species?? forests has not received enough attention in the literature so far. The neighborhood seedling model was used to fit pollen dispersal models for beech at different stages of gap recolonization and to elucidate the effect of saplings as a physical barrier on pollen dispersal at local scale. Phenological overlap of leaf emergence, and pollen release as well as wind directionality patterns were also examined. As a case study, we used a mixed beech-oak forest that was managed as open woodland until 1974. The ban on entry of cattle has led to the recolonization of empty spaces by seedlings and saplings of beech (Fagus sylvatica L.) and two oak species (Quercus petraea (Matts.) Liebl. and Q. pyrenaica Willd.) and, at last, to canopy closure. The average pollen dispersal distance for the first plants that regenerated in the gaps was almost twice those found for recently installed seedlings and seeds collected in traps, supporting the hypothesis that the understory may act as a physical barrier to pollen dispersal. Although a substantial part of effective pollination directionality is at random, horizontal winds and vertical anabatic winds may explain some of this directionality. At the time of beech pollen release, leaves of beech and sessile oak are fully developed, enhancing pollen interception by the saplings. Explicit models of pollen dispersal for wind-pollinated trees should incorporate the effect of canopy closure caused by growth of saplings and account for leaf phenology of co-occurring species in the forest.     

Dispersal of spores and pollen from crops

Fungal spores and pollens can be dispersed in a number of ways: by animals and insects; by water; by wind or by rain. This paper concentrates on the effects of wind on the dispersal of spores and pollen grains and the effects of rain on spore dispersal. For dispersal to be successful particles must complete three phases: removal, dispersal through the air and deposition. The biology of the organism and its environment can affect all three phases, however, once released the fate of all airborne particles largely depends on the laws of physics which govern the motion of the air. Many types of spore are actively ejected into the air while others are simply blown from the host surface. Particle size and shape affects dispersal and deposition phases. Local environmental factors such as temperature, humidity and light, as well as wind or rain, can play a key role in the removal of spores. Wind speed and turbulence or rainfall, largely determine spore dispersal, but, the size and shape of the particle, the nature of the plant canopy and the way the particles are released into the air may also be important. Particle deposition depends on both environmental and biological factors. This paper briefly considers these processes using examples and how they can be modelled.     

Ragweed and mugwort pollen in Szczecin, Poland

Ragweed (genus Ambrosia) and mugwort (Artemisia vulgaris) pollen grains are known to be very potent aeroallergens, often noted to enter into cross reactions. The aim of the study was to analyse ragweed and mugwort pollen release in Szczecin (western Poland) during the period 2000–2003. Measurements were performed by the volumetric and gravimetric method. Pollen seasons were defined as the periods of 90% of the total catch. Of the 4 years studied, the lowest concentration of ragweed pollen was observed in 2000. In 2000, the annual ragweed pollen count was very high, threefold higher than in 2001. There was a high Ambrosia pollen count in 2003, with the highest daily value of 84 grains/m³. The mugwort pollen season started in the third 10-day period of July and lasted to the end of August in all of the years studied. Analysis of pollen deposition from different Szczecin city’s districts showed that the highest exposure to ragweed pollen allergens occurred in the Majowe district, which is related to the presence of numerous plants of Ambrosia in that district. The mugwort pollen deposition was more abundant in the Żelechowa district, which is an area with villas and gardens. Statistically significant correlations were found between the ragweed pollen count in the air and the maximum wind speed, air temperature and relative humidity and between the mugwort pollen count in the air and air temperature and relative humidity.