Effect of pollination time,the hour of daytime,pollen storage temperature and duration on pollen viability,germinability, and fruit set of date palm (Phoenix dactylifera L.) cv "Deglet Nour"

Success artificial pollination with viable pollen is crucial process in the production chain of date palms. This study evaluated the impact of pollen storage temperature and duration, pollination time following spathe cracking, and the hour of daytime on pollen viability, germinability, fruit set and yield of 'Deglet Nour' date palm cultivar. In in vitro tests, fresh pollen showed the maximum viability (96.3%) and germination (85%) but it decreased thereafter upon the storage temperature (28, 4 and ?30 °C) and duration (3, 6, 9 and 12 months). In this respect, pollen stored at ?30 °C retained highest viability and germinability followed by those stored at 4 and then at 28 °C. In filed experiments, fruit set was 85, 75, 65, and 45% with pollination using fresh pollen, or pollen stored at ?30, 4 and 28 °C, respectively. Fruit set was 95%, 75%, and less than 50%, for pollination performed on the same day of spathe cracking, 6 and 12 days later, respectively. The highest fruit set percentage and yield/bunch were obtained with pollination performed between 12.0 pm and 15.0 pm in contrast to 8.0–11.0 am or 16.0–17.0.     

Influence of season on rose pollen quality

Summary In vitro tests of pollen germination were carried out at different periods during an annual cycle in order to study environmental influence on the quality of Rosa hybrida L. pollen during its maturation process. This quality was evaluated by taking into account the rate of germination as well as the average length of emitted pollen tubes. In addition, during an annual hybridization period, a few pollinations were carried out in vivo with pollen of the same origin in order to study the evolution of the fertilization results, as attested by number of achenes per resulting hips. During the period covered by the experiments, the evolution of the pollen quality detected in vitro can be related to that of seed setting success. Of the two criteria used in vitro to evaluate pollen quality, the factor most liable to influence in vivo fertilization success seems to be the average length of emitted pollen tubes.     

Effects of pollen quality and quantity on pollen limitation in Crataegus monogyna (Rosaceae) in NW Spain

Pollen limitation occurs when plants produce less fruits and/or seeds than they would with adequate pollen receipt. If the addition of cross-pollen to stigmas increases fruit/seed production, it is interpreted as an evidence of pollen limitation. Much of the limitation may be associated with the quality rather than quantity of pollen; however, most studies do not discriminate between the two, which may lead to misinterpretation of the results. We studied the effects of quality and quantity of pollen on the reproduction of a northern Spanish population of Crataegus monogyna. The treatments included self- and cross-pollination, and supplementation to open and bagged flowers. The response variables considered were number of pollen grains per stigma, pollen tubes per style, and initial and final fruit set. In the Cantabrian range, C. monogyna requires insect pollinators to set fruit and is partially self-incompatible. We found that the number of pollen tubes did not differ between cross- and self-pollination treatments; however, self-pollinated flowers set less fruits than flowers that received pure cross-pollen or were supplemented with both cross- and self-pollen. The experimental design allowed us to infer qualitative rather than quantitative pollen limitation. Comparison of the number of pollen grains and tubes, and initial and final fruit set among pollination treatments suggested post-zygotic embryo selection against selfed progeny.     

Effect of male inflorescence of Castanea mollissima on the reproductive development and lifetime of Bactrocera minax

Previous work reveals that newly emerged adult Chinese citrus flies, Bactrocera minax (Enderlein), emerges from the ground in the mosaic-type citrus orchard of the hilly terrain landform dispersed into adjacent forest, and the newly emerged adult flies fed on male inflorescence of the Chinese chestnut, Castanea mollissima Blume (Fagaceae). The potential impact of male inflorescence of C. mollissima on the longevity, and survival of adult females and males, the ovarian development of adult females, and the abdominal index, ovarian index, and egg length of the fourth ovarian grade of living females, as well as the flowering process of the male inflorescence of the Chinese chestnut, were studied with the three methods of rearing (normal rearing, hungry rearing, and bagging rearing). For all three rearing treatments, the longevity of all adults could live up to 38 days, there were similar time dynamics for the average survival of female and male adult flies. Of the total females, 32.1%–100% females with bagging rearing could attain the fourth ovarian grade like those in rearing and hunger rearing. The abdominal index, ovarian index, and egg length of the fourth ovarian grade of 27–39 days’ old living females with bagging rearing (it corresponds to the late flower withering period), were 75.1%, 49.8% and 89.6% of those with normal rearing, and 73.2%, 60.6% and 90.8% of those with hungry rearing, respectively. The male inflorescence of C. mollissima can satisfy the nutritional requirements of adult B. minax, enabling their survival and normal reproduction. This study can provide references for development and application of artificial feed and food attractants of adult B. minax.     

Production of fertile tobacco pollen from microspores in suspension culture and its storage for in situ pollination

Summary A simple procedure is described for the in vitro production of tobacco (Nicotiana tabacum L.) pollen from microspores isolated just before entering mitosis. During a 3-day culture period in a liquid medium containing pyrimidine nucleosides these microspores develop into young pollen grains to the stage of starch deposition. Pollen maturation and transition to dormancy is achieved during a further 2- to 3-day culture period in the same medium stepwise supplemented by a concentrated solution of sucrose and l-proline. Upon transfer of the pollen to a simple germination medium containing sucrose and boric acid, up to 40% of the grains were observed to produce relatively long tubes. The in vitro-matured pollen grains can be stored at-20° C either suspended in 1.17 M sucrose and 100 mM l-proline or separated from the medium on filter paper discs. The stored pollen germinated both in vitro and on the stigma, the pollen tubes grew through the style into the ovary and pollination produced up to 300 viable seeds per pod. The procedure is of interest for pollen developmental studies and various fields of pollen manipulation, such as in vitro pollen selection.     

低温贮存对椰心叶甲啮小蜂品质的影响

研究低温贮存椰心叶甲蛹Brontispa longissima(Gestro)和椰心叶甲僵蛹对椰心叶甲啮小蜂Tetrastichus brontispae Ferriere种群品质的影响。寄生10℃低温贮存1~4日龄椰心叶甲蛹结果表明,1日龄椰心叶甲蛹的寄生率、羽化率、出蜂率、单蛹出蜂数、后代寄生能力均优于其他日龄,其次为2、3日龄的椰心叶甲蛹,最差为4日龄的椰心叶甲蛹。1日龄椰心叶甲蛹在10℃下贮存5,10,15,20d后,上述生物学指标和种群参数均随贮存天数增加而降低,其中以5d和10d的净生殖率、内禀增长率和周限增长率较未经低温贮存的差异小。1~11日龄椰心叶甲僵蛹于10℃贮存10d的结果表明,8日龄椰心叶甲僵蛹的雌蜂寿命、羽化率、单蛹出蜂数、寄生能力均优于其他日龄僵蛹。8日龄椰心叶甲僵蛹在10℃下贮存5,10,15,20d后,上述生物学指标和种群参数均随贮存天数增加而显著低于对照。     

Influence of wind direction on pollen concentration in the atmosphere

The daily pollen concentration in the atmosphere of Badajoz (SW Spain) was analysed over a 6-year period (1993–1998) using a volumetric aerobiological trap. The results for the main pollination period are compared with the number of hours of wind each day in the four quadrants: 1 (NE), 2 (SE), 3 (SW) and 4 (NW). The pollen source distribution allowed 16 pollen types to be analysed as a function of their distribution in the four quadrants with respect to the location of the trap. Four of them correspond to species growing in an irrigated farmland environment (Amaranthaceae-Chenopodiaceae, Plantago, Scirpus, and Typha), five to riparian and woodland species (Salix, Fraxinus, Alnus, Populus, and Eucalyptus), four to urban ornamentals (Ulmus, Arecaceae, Cupressaceae, and Casuarina), and three which include the most frequent pollen grains of widely distributed species (Poaceae, Quercus, and Olea). The results show that the distribution of the sources and the wind direction play a very major role in determining the pollen concentration in the atmosphere when these sources are located in certain quadrants, and that the widely distributed pollen sources show no relationship with wind direction. In some years the values of the correlations were not maintained, which leads one to presume that, in order to draw significant conclusions and establish clear patterns of the influence of wind direction, a continuous and more prolonged study will be required. Received: 6 May 1999 / Revised: 30 March 2000 / Accepted: 31 March 2000     

Ultrastructure of sperm cells and the male germ unit in pollen tubes ofNicotiana tabacum

Summary The structure of sperm cells and their association with the vegetative nucleus in pollen tubes ofNicotiana tabacum grown in styles were observed with the electron microscope, demonstrating the existence of a male germ unit. The two sperm cells are arranged in tandem and are closely associated with the vegetative nucleus, which always takes the lead. The leading sperm cell (SC 1) has a long and narrow cytoplasmic projection which lies within the enclaves of the much lobed vegetative nucleus, thus forming a physical association. The trailing sperm cell (SC 2) and the SC 1 are not only joined by a common transverse cell wall but also are surrounded by a periplasm bounded by the plasma membrane of the sperm cells and that of the vegetative cell, thus forming a structural connection. The sperm cells are elongated, with cytoplasmic projections at the anterior end of the SC 1 and at both ends of the SC 2. The cytoplasm of both sperm cells includes mitochondria, endoplasmic reticulum, dictyosomes, ribosomes, small vacuoles and axially oriented microtubules. No plastids were observed.Abbreviations DAPI 4,6-diamino-2-phenylindole - MGU male germ unit - MT microtubule - SC 1 the leading sperm cell physically associated with the vegetative nucleus - SC 2 the trailing sperm cell     

First record and preliminary evaluation of Mucor hiemalis as biocontrol agent on inflorescence brown rot incidence of date palm

In Egypt, inflorescence brown rot disease of date plam trees caused by Thielaviopsis paradoxa De Syenes causing high losses of pollen grains and fruits yield productivity. Infection occurs early on spathes even when it still hidden in the leaf bases. White mycelium of pathogenic fungi grows on inflorescence then turned to brown when fungus spores abundant. Isolation trails from diseased spathes showed brown rot, yielded three genus of fungal i.e. Aspergillus niger (25%), Mucor hiemalis (25%) and T. paradoxa (50%). Pathogenicity test by using fungal isolates and male inflorescence of data indicate that, all isolates of T. paradoxa were able to induce brown rot of inflorescence. Isolates of T. paradoxa were differed in pathogenic activity for producing inflorescence brown rot symptom. Also, A. niger isolate could cause slightly decay on inflorescence. Meanwhile, all isolates of M. hiemalis recorded as non pathogenic. In vitro, dual culture technique by using M. hiemalis showed antagonistic properties against T. paradoxa. Scanning electron microscopy (SEM) study revealed that, pollen grains of date palm are susceptible to infection by T. paradoxa, accompanied by complete lyses and ruptured. SEM examination of inflorescence treated by each of M. hiemalis or/and T. paradoxa showed that M. hiemalis was able to colonisation on inflorescence and reduced colonisation of T. paradoxa on inflorescence and pollen grains. Preliminary evaluation of M. hiemalis as a biocontrol agent showed that, spray of inflorescence with M. hiemalis suspension two days before or after infestation by T. paradoxa were reduced brown rot of inflorescence than the control. Spraying of spathes by M. hiemalis before infestation by pathogen was highly effective in reduction brown rot incidence compared with spraying after infestation. These results help to explain the role of M. hiemalis in the suppression and biological control of T. paradoxa.     

Origin of sperm cell association in the “male germ unit” ofBrassica pollen

The association of the two sperm cells inBrassica napus pollen following the generative cell division was investigated. The generative cell during division is located in the center of the pollen grain, within the vegetative cell. The space present between the two cells is slightly irregular as seen following standard glutaraldehyde fixation. After completion of mitosis vesicles appear in the equatorial plane, coalescing centripetally to form a cell plate which fuses with the membrane of the generative cell, dividing it in two sperm cells. They are isolated from the vegetative cell by the space between the two cell membranes and are separated from each other by a similar space resulting from the cell plate formed during cytokinesis.     

Declining viability and lipid degradation during pollen storage

Declining viability of pollen during storage at 24° C in atmospheres of 40% relative humidity (RH) and 75% RH was studied, with special emphasis on lipid changes. Pollens of Papaver rhoeas and Narcissus poeticus, characterized by a high linolenic acid content, were compared with Typha latifolia pollen which has a low linolenic acid content. The rationale behind this was to answer the question of whether lipid peroxidation is involved in the rapid viability loss and reduced membrane integrity of, in particular, the unsaturated-lipid pollen types. Viability and membrane integrity degraded more rapidly at 75% RH than at 40% RH. All pollen species showed deesterification of acyl chains of lipids but no detectable peroxidation at both RH levels. Considerable amounts of lipid-soluble antioxidants were detected that did not degrade during storage. Free fatty acids and lysophospholipids were formed during storage, the effects of which on membranes are discussed. These degradation products were very prominent in the short-lived Papaver pollen. The loss of viability does coincide with phospholipid deesterification. A significant decrease of the phospholipid content occurred at 75% RH, but not at 40% RH. Based on compositional analyses of phospholipids and newly formed free fatty acids, it was concluded that the deesterification of acyl chains from the lipids occurred at random. We suggest that, due to the low water content of the pollen, free radicals rather than unspecific acyl hydrolases are involved in the deesterification process.     

Effects of water stress on male gametophyte development in plants

 Male reproductive development in plants is highly sensitive to water deficit during meiosis in the microspore mother cells. Water deficit during this stage inhibits further development of microspores or pollen grains, causing male sterility. Female fertility, in contrast, is quite immune to stress. The injury is apparently not caused by desiccation of the reproductive tissue, but is an indirect consequence of water deficit in the vegetative organs, such as leaves. The mechanism underlying this stress response probably involves a long-distance signaling molecule, originating in the organs that undergo water loss, and affecting fertility in the reproductive tissue, which conserves its water status. Much research has been focused on the involvement of abscisic acid in this regard, but the most recent evidence tends to reject a role for this hormone in the induction of male sterility. Stress-induced arrest of male gametophyte development is preceded by disturbances in carbohydrate metabolism and distribution within anthers, and an inhibition of the key sugar-cleaving enzyme, acid invertase. Since invertase gene expression can be modulated by sugar concentration, it is possible that decreased sugar delivery to reproductive tissue upon inhibition of photosynthesis by stress is the signal that triggers metabolic lesions leading to failure of male gametophyte development. Received: 31 October 1996 / Revision accepted: 18 February 1997     

Low legitimate pollen flow in distylic Turnera hermannioides (Passifloraceae) and its consequences on fruit and seed set

Turnera hermannioides is a ruderal distylic subshrub, native to NE-Brazil. In the Catimbau National Park, situated within the semi-arid Caatinga region, we studied the pollination ecology of this species, emphasizing (1) effective pollinators; (2) characteristics of short- and long-styled flowers; (3) intra- and intermorph pollen flow; and (4) fruit and seed set. Short and long-styled morphs differ in pollen size and ornamentation, stigmatic surface, style and stamen length and nectar production. The flowers are obligate intermorphic outcrossers and depend on animals for pollination. The flowers of T. hermannioides attracted insect visitors of 25 species, among them butterflies, beetles, but mainly bees. Polylectic bees, such as Apis mellifera, stingless bees, and solitary Callonychium brasiliense were the most frequent visitors and the principal pollinators. The frequency of visits, however, was very low (on average 1.9 visits/flower/day), resulting in a low and unbalanced legitimate pollen flow, i.e. a much lower number of pollen grains from short-styled flowers reaching stigmas of long-styles than vice versa, which in turn compromised fruit and seed set. Surprisingly, Protomeliturga catimbaui and P. turnerae, both oligolectic on flowers of the Turneraceae-clade of the Passifloraceae s.l., were very rare flower visitors and did not contribute significantly to the pollination of Turnera hermannioides. We discuss how the low visitation rate and the inefficiency of pollinators (i.e. inefficiency in promoting legitimate pollination) compromise pollen flow and, consequently, fruit and seed set in this species.     

Emerging data on pollen tube growth and fertilization in flowering plants, 1990–1995

Summary Since its discovery at the end of the last century, double fertilization remains of central interest in plant reproductive biology research. Although the sequence of events leading to fertilization is well known from cytological studies, the underlying mechanisms remain to be elucidated. This now seems feasible by the diversification and refinement of recently developed technologies presented in this review. The progress made during the last five years in understanding pollen tube guidance, discharge into the embryo sac, and gametic fusion are described. Future directions are also discussed.Dedicated to Prof. Dr. Dr. h.c. Eberhard Schnepf on the occasion of his retirement     

日光温室切花郁金香花期与外观品质预测模型

光温是影响花卉作物花期和外观品质的重要环境因子。本文目的是建立日光温室切花郁金香花期与外观品质预测模型,以期通过调节种植期和种植密度,实现日光温室切花郁金香生产的光温优化调控。本研究以郁金香品种世界珍爱(Tulip gesneriana cv ‘World Favorite’)和金检阅(Tulip gesneriana cv ‘Golden Parade’)为试材,通过不同种植期和不同密度的栽培试验,定量分析了种植期和密度对郁金香发育进程及外观品质动态的影响。在此基础上,以单株吸收辐热积(Photo-thermal Index,PTI)为尺度,建立了日光温室切花郁金香花期与外观品质预测模型,并用独立的试验数据对模型进行了检验。结果表明,模型对郁金香花期和各外观品质指标的预测效果较好。模型对各生育时期的预测值与实测值之间的决定系数R2为0.95,对萌芽期、展叶期、现蕾期和采收期的预测值与实测值的回归估计标准误RMSE分别为0.7、1.3、2.9和1天。模型对株高、展叶数、茎基长度、茎基粗度、花颈长度、花颈粗度、花蕾长度和花蕾直径的预测值与实测值之间R2分别为0.97、0.97、0.98、0.98、0.98、0.97、0.98和0.97,RMSE分别为30.8mm、0.2、3.5mm、0.1mm、5.5mm、0.1mm、1.2mm和0.4mm。模型对A、B、C级出花率的预测值与实测值之间的R2分别为0.95、0.97、0.96,RMSE分别为0.8%、0.3%、0.9%。本研究建立的模型预测精度较、高参数少,可为日光温室切花郁金香生产中种植期和种植密度的优化提供理论依据和决策支持。     

Simultaneous estimation of pollen contamination and pollen fertilities of individual trees in conifer seed orchards using multilocus genetic data

Seed orchards of forest trees are established to produce genetically-improved seed for reforestation. Genetic efficiency requires seed orchards to be (1) reproductively isolated form surrounding trees, (2) that there be similar fertilities among all orchard trees, and (3) minimum inbreeding. Each aspect of seed orchard reproduction can be simultaneously estimated using the observed frequency of each multilocus gametic type contributed through fertilizing pollen and the expected multilocus gametic segregation frequencies of orchard tree and of the contaminating population. These genetic estimates are directly relevant to the genetics of the tree breeding program. The flexibility of sampling seed — the basic data for these techniques — allows great scope for hypothesis testing, including tests of the accuracy of predictions of biophysical models of pollen movement. A simple example and a white spruce seed orchard case study are presented to illustrate the estimation technique and to investigate its sensitivity.     

Structural, histochemical, and protein analysis of male reproductive development in willow

Information on the development of the male reproductive structures in willow will help advance our understanding of its reproductive behavior and contribute to our ability to work towards its improvement. Willow also offers the opportunity to study male sterility, a subject matter which is not typically dealt with in woody plants. As compared to the three willow species examined (Salix eriocephala, S. exigua, and S. purpurea), pollen development in S. discolor S365 showed several abnormalities starting with the delay in meiosis. This lasted for about 10 days and meiosis eventually occurred as manifested by the formation of microspores. However, most of the resulting microspores collapsed, while only a few developed into pollen grains. The large number of undeveloped and disintegrated microspores appeared to make the few pollen grains sticky, preventing them from being dispersed. Histochemical analysis showed that meiosis in most species of willow was associated with the presence of large amounts of insoluble polysaccharides in the anther wall layers, but only very few of these were observed in S. discolor. Also, a 32-kDa protein which is the most abundant protein in the reproductive structures of willow, was absent in S. discolor S365. Proteomic analysis showed that this is similar to the storage proteins in Populus x canadensis and P. deltoides. Therefore, male sterility in S. discolor may be due to some genetic defects affecting the accumulation of essential reserves in its reproductive structures. The mechanism behind this is unknown, but this study has established the nature of sterility in S. discolor S365.     

Morphology and lateral germination of pollen in Ginkgo biloba and their implications in evolution

The four-celled mature pollen of Ginkgo biloba L. just shed from the microsporangia, was round in shape and contained a very large germination area with monosulcate sulcus walled with two semicircular and nearly perpendicular parts of exine, and the pollen was coated with a compact irregular striations and spinules in parts other than the germination area. The pollen became boatshaped and was bilaterally symmetrical when it was in air or under cold storage, but rapidly rounded off in cultural solution. Studies on early morphogenesis of the male gametophyte in vitro and in vivo revealed that the tube nucleus turned a certain degree of angle, and was followed by lateral germination, while the non-active pollen maintained its round shape. The results suggest that the internal feature of the pollen tube could be a determinant factor contributing to the expression of the characteristic events of lateral germination of the male gametophyte in G. biloba. Furthermore, this biologically consistent character, together with the characteristic pollen morphology, is quite different from those of other groups in gymnosperms such as Cycas and Pinus. This might be a critical characterrelevant to the systematic position of G. biloba.     

Influence of flower functionality and pollination system on the pollen size-pistil length relationship

Twenty-five biotically pollinated plants of the Chaco Serrano Forest (Córdoba, Argentina) were studied in order to analyze whether ‘flower functionality’ is related to the relationship between pollen size and pistil length. Because flower functionality may act on the respective mean values of pollen size and pistil length rather than on intraspecific variation in these traits, we expected (1) a high positive correlation between pollen size and pistil length in a set of sympatric species, independent of their degree of pollination specialization or generalization; and (2) no interspecific correlation between the coefficients of variation (CVs) of those traits. On the other hand, on the assumption that pollinators are influencing the variation in floral traits (e.g. in pistil length) we expected lower mean phenotypic variation of pollen size and pistil length in pollination-specialist plants than in pollination-generalist ones. A positive correlation between pollen size and pistil length was found for the set of species, but not between the CVs of these traits. This trend was maintained when pollination-specialist plants were analyzed separately, but no statistical significance was obtained for the correlation in pollination-generalist plants. Contrary to our expectations, pollination-specialist plants did not show less mean intraspecific variation in floral traits than pollination-generalist plants. Therefore, the relationship between pollen size and pistil length among species suggests that the pollination system may be of less importance as a selective force than flower functionality.     

Effect of planting date on flowering time in wheat

The time from seed germination to anthesis varied for spring wheat in experiments in climate chambers with plants grown hydroponically at different nitrogen regimes. Time to anthesis was related to the time of seed germination during the calendar year. Seed germinating earlier in the calendar year required a shorter time to anthesis compared to seed germinating later in the year, a pattern found for all the spring wheat cultivars investigated. Time to anthesis was also found to be independent of factors such as year in which the seed was produced, nitrogen regime used, or year or site of cultivation. We suggest the existence of an annual rhythm for flowering in spring wheat. This variation in time to flowering can be due either to external factors or more likely to an endogenous rhythm in the plant. When investigating plant processes, it is of importance to be aware of such a rhythm, since it may influence the results depending on when during the year the experiments are performed.