Storage of avocado pollen

Summary Avocado pollen was stored at a range of temperatures and relative humidities (RH) for up to one year and the pollen was tested for viability in vivo.Pollen stored for one month was capable of germination on the stigma and penetrating the ovule when stored at 4°C with <1,23,55 and 75% r.h. and at -196°C with 0% r.h. Most pollen samples stored at 25 and -15°C at a range of r.h. would germinate on the stigma but none would penetrate the ovule.After one year of storage, pollen at 4°C and <1 and 23% r.h. would germinate on the stigma but would not penetrate the ovule. There was no germination of pollen stored at 4°C and 55 and 75% r.h. Only pollen stored at -196°C and 0% r.h. would penetrate the ovule, but thawing and refreezing once during the year destroyed the viability.     

Inter-varietal pollen tube growth and ovule penetration in the avocado

Summary Results are presented showing number of pollen tubes in the pistil, and ovule penetrations in crosses involving the avocado varieties Edranol, Ryan, Hass, Reed, Talbot, Jalna, Fuerte, Bacon and Sharwil. Between 5% and 100% of the ovules in each cross were penetrated by a pollen tube. The female parent exerted more control than the male on numbers of tubes and ovule penetrations and the results for type A varieties were more consistent than those for type B varieties. Penetration of an ovule by two tubes was observed in all varieties except Reed and Fuerte and penetration of an ovule by three tubes was observed in the variety Edranol only. With the possible exception of the variety Bacon as female parent there was no difference between pollination with pollen from type A or B varieties.     

In vitro germination and viability of buckwheat (Fagopyrum esculentum Moench) pollen

An in vitro method for the germination of common buckwheat pollen was developed. Pollen grains were successfully germinated in an artificial medium consisting of 0.2 g each of MnSO₄, Ca(NO₃)2.4H₂O and KNO₃, 0.04 g H₃BO₃, 15 g sucrose and 30 g polyethylene glycol (molecular weight approximately 20,000) dissolved in 100 ml of double distilled water. The viability of pollen was assessed by in vivo and in vitro germination tests at 20 °C and 25 °C over a 38 h time period. Pollen grains were collected and germinated at 4 h intervals from freshly harvested flowers grown under 16 h day length and a constant temperature. Maximum pollen viability was found 2 h and 6 h after first light when plants were maintained at 25 °C and 20 °C, respectively. Viability, as measured by germination percentage, was similar at both temperature regimes. Some pollen remained viable for approximately 34 to 38 h in intact flowers, but all pollen lost viability in less than an hour when stored at room temperature without humidity control. This revised version was published online in July 2006 with corrections to the Cover Date.     

Establishment of reliable methods of in vitro pollen germination and pollen preservation of Brassica rapa (syn. B. campestris)

A simple and reliable method for evaluating the viability of Brassica pollen was established in which the in vitro germination rate of pollen was adopted as the index of the viability of pollen grains. Pollen grains were preincubated in an atmosphere in which the relative humidity (RH) was fixed to 52% or 66% at 20 °C for 5 hours. They were cultured for 16 hours at 25 °C in a liquid Kwack's medium (1964) supplemented with 20% sucrose, and the pH was adjusted to 8.0. They were then observed under a microscope and the number of germinating and unchanged pollen grains were counted. The germination rate of pollen was improved and stabilized by preincubation and the use of a high pH medium. More than 90% of the freshly harvested pollen grains of Brassica rapa (syn. B. campestris) germinated constantly in these conditions Undehisced anthers were collected from flowers at anthesis and dehydrated by incubation at 20 °C for 16–24 hours in an atmosphere where the RH was fixed to 15% or 32%. They were put into a plastic vial and preserved in a freezer at -20 °C. The germination percentage of the preserved pollen was scored at intervals during preservation. The germination rate of the pollen grains preserved at -20°C for 1 year was higher than 50% and the pollen proved to be efficient for seed set. Most of the seeds germinated normally. This revised version was published online in August 2006 with corrections to the Cover Date.     

An assessment of thein vitro germination capacity of pollen grains of five tea hybrid rose cultivars

Summary Germination trials of pollen grains of the tea hybrid rose cultivars: Ferry Porche, Bronze Masterpiece, Queen Elizabeth, John F. Kennedy and Lady X, were carried outin vitro, to determine whether these cultivars are suitable as pollen donors in a breeding programme.Pollen grains of all five cultivars germinated poorly in a medium containing sucrose only. Addition of boric acid in the medium improved the germination percentages. The highest germinability was observed in Ferry Porche and Lady X on 15% sucrose+50 ppm boric acid, and 20% sucrose+100 ppm boric acid, respectively. Addition of calcium nitrate in the medium reduced germination percentages in all cultivars.The effect of pH of the medium on pollen grain germinability depended on the cultivar and the composition of the medium. On a medium free of boric acid, the pH values between 5.5 and 7.0 caused a significant increase in the germination percentages of pollen grains of Lady X and Queen Elizabeth. The addition of boric acid decreased the responsiveness of the pollen of all cultivars to the pH changes of the medium.The germination capacity of pollen grains of Lady X and Ferry Porche was not affected by incubation temperatures ranging between 20°C and 30°C.On the basis of the above results Lady X and Ferry Porche are considered the most suitable for pollen donors.     

Effects of gamma irradiation on in vitro pollen germination of different Cucumis species

Summary Pollen grains of 14 Cucumis accessions were irradiated with 0, 1, 2, 3 or 4 kGy acute gamma rays and germinated in vitro directly afterwards. Pollen germination was significantly reduced by increasing irradiation dose for all species, except C. melo var. agrestis. Pollen tube growth was generally reduced likewise. Pollen of two C. anguria subspecies was most sensitive to irradiation. Sensitivity of the pollen with respect to pollen tube growth in relation to irradiation dose was inversely related to total DNA amount per nucleus. In vitro germination was not related to DNA amount per nucleus. Results show that the examined Cucumis species, especially C. melo var. agrestis, are sufficiently resistant to irradiation to be used as donor species for in vivo egg cell transformation of the cucumber.     

Effect of humidity and temperature on power electric field intensity

We measure power electric field intensity at a substation in southwestern P. R. China at various humidity levels and temperatures. Measurement data and a back propagation neural network are used to construct a model of electrical field intensity responses to fluctuations in humidity and ambient temperatures. The maximum error is 0.047 5. The results show that the power electric field intensity increases as humidity rises when the temperature is constant; when humidity is a constant, temperature changes do not affect the regularity of the electric field intensity in a consistent manner regularly.     

In vitro pollen germination and tube growth of tomato (Lycopersicon esculentum Mill.) and its relation with plant growth

Summary In vitro pollen germination at 10°C, 14°C and 22°C of four groups of two pure line tomato varieties was compared with their plant growth at 19°C D/10°C N under controlled environmental conditions. Generally, pollen germination was slow at 10°C but after 6 h the percentage of germination was similar to that at 22°C. Maximum germination was obtained at 14°C already after 4 h. The longest pollen tubes occurred at 22°C. The two varieties within each group differed significantly from each other for percentage of pollen germination. For one group, this difference was greater at 10°C than at 22°C. The varieties in two groups also differed significantly for pollen tube growth. These differences in pollen tube growth rate were greater at 22°C than at 10°C. There was no clear relationship between pollen germination, pollen tube growth and plant growth in any of the four pairs of varieties. The results are discussed with regard to the possibility of pollen selection at low temperature in order to improve the efficiency of breeding for growth at low temperature.     

Low temperature tolerance of biomass and pollen germination in potato clones of Andean and European origin

Summary The temperature-related performances of six tetraploid potato clones, two Andean, three European, and one hybrid, were compared by cultivating them in growth chambers under one of two temperature regimes: 10°C day/4°C night or 20°C day/10°C night. Preformance was measured in terms of biomass production and pollen germinability.For dry matter yield at second harvest, the temperature-related performance ratios (performance at 10°C/4°C divided by performance at 20°/10°C) were highest for the Andean clones, intermediate for the Andean/European hybrid clone 201₅×S₁₂, and lowest for the European cultivars. The ability of the European cultivars to maintain their normal rates (i.e. rates at 20/10°C) of biomass production when cultivated at low temperatures varied greatly, with clone S₃ performing most poorly at 10/4°C.For pollen germinability in vitro, performance ratios were highest for the hybrid clone 201₅×S₁₂ and lowest for the European clones.The high tuber yield of hybrid 201₅×S₁₂ at 10/4°C can be attributed to its low-temperature tolerance and it being daylength neutral.     

Differential cold sensitivity of pollen grain germination in two Prunus species

Summary Pollen grains from selected cutivars of almond [Prunus dulcis (Mill.) D. A. Webb] and peach (Prunus persica Batsch L.) were exposed to a range of temperatures between 1°C and 34°C on a thermogradient plate. Pollen germination at temperatures below 9°C was conspicuously greater in almond than peach. Miximal germination percentages were attained at about 16°C (almond) and 23°C (peach). The two species did not differ in their capacity for pollen tube elongation over a broad range of temperatures. Maximal pollen tube elongation occurred at temperatures 5°C to 8°C higher than maximal pollen germination. Species affiliation appeared to be of much greater consequence than chilling requirement or bloom date of the sporophyte in predicting gametophytic response to temperature.     

Effects of desiccation and a change in temperature on germination of immature grains of wheat (Triticum aestivum L.)

A study was made of the effects of desiccation and a change in temperature on the germination of wheat grains harvested 20 days after anthesis. When the germination test was performed immediately after harvesting, germination percentages ranged from 5.2% to 10.7%. Germination percentages increased to 48.2% to 90.3% after grain had been desiccated at 20 °C and then hydrated at 10 °C. This increase occurred even if grains had been desiccated in an atmosphere of high relative humidity. The germination percentage of non-desiccated grains depended on the germination temperature. When the pericarp and testa were removed from embryos, the germination percentage of grains incubated at 20 °C and then at 10 °C was higher than that of grains incubated at 10 °C. In general, a low germination temperature is believed to be effective in breaking dormancy of wheat grains. However, a change in temperature stimulated germination to a greater extent than a constant low temperature. The germination percentage of 5-day cycle alternating temperature was greater than that with 1-day, 2-day and 10-day cycles. Although the germination of immature wheat grains was stimulated by both high and low germination temperatures, it is likely that cycles shorter and, also, longer than a critical period induce limited germination. Loss of dormancy commonly occurs when development of wheat grains proceeds at a high temperature, with imbibition at a low temperature. However, germination ability of non-desiccated immature wheat grain was enhanced by a change in temperature during germination. This revised version was published online in August 2006 with corrections to the Cover Date.     

Factors affecting haploid production in wheat using the Hordeum bulbosum system. 1. Genotypic and environmental effects on pollen grain germination,pollen tube growth and the frequency of fertilization

Summary A quantitative examination of pollen grain germination and pollen tube growth within the overy wall was made in selected wheat × tetraploid H. bulbosum hybridizations, to investigate the effect of the wheat and the H. bulbosum genotype on these characters. As expected, variation at the known crossability loci had no effect on pollen grain germination. The frequency of pollen tube penetration of the ovary wall was, however, severely reduced when the dominant alleles were present. Pollen tube penetration was nevertheless observed in 3 of the 110 ovaries examined of the non-crossable cultivar Highbury. The H. bulbosum genotype had a much smaller effect on these characters, but significant differences between the clones were observed in the numbers of pollen tubes initially penetrating the ovary wall. Although two H. bulbosum genotypes showed no significant differences in the number of ovaries with pollen tubes at the base of the ovule, significant differences in the frequency of fertilization were observed. The possible cause of this discrepancy is discussed.The frequency of fertilization in crossable wheat × H. bulbosum hybridizations was improved by the application of gibberellic acid within 10 minutes of pollination, and reduced by an increase in the ambient temperature from 20°C to 26°C. Fertilization following the pollination of non-crossable wheat genotypes was not affected by either of these factors.     

植物生长调节剂对‘秦冠’苹果花粉管生长和花粉萌发的影响

研究吲哚乙酸、萘乙酸、赤霉素、2,4-D、6-BA5种植物生长调节剂对苹果花粉管生长和花粉萌发的影响。以贮藏6个月的‘秦冠’花粉为材料,配制不同浓度梯度植物生长调节剂的固体培养基培养花粉,研究不同浓度植物激素对花粉管生长和花粉萌发的影响。结果表明,当吲哚乙酸≤1 mg/L、萘乙酸≤1 mg/L、6-BA≤5 mg/L、赤霉素≤10 mg/L时对花粉萌发有轻微促进作用,当浓度增大时抑制作用较突出;2,4-D对花粉萌发存在明显抑制作用;当赤霉素、2,4-D、吲哚乙酸、萘乙酸、6-BA浓度分别达到50、30、30、15、25 mg/L时,花粉遭受浓度迫害出现畸形扭曲。吲哚乙酸、萘乙酸、赤霉素、2,4-D、6-BA对‘秦冠’花粉管生长和花粉萌发均无明显促进作用,并且随浓度增大抑制作用较明显,人工辅助授粉时用于添加剂效果不理想。     

循环通风对白肋烟晾制期间晾房内温湿度的影响

为改进白肋烟晾制技术,利用温湿度自动记录仪定时测量白肋烟晾制期间晾房内的温度和相对湿度,在晾房内加装循环通风风机调控温湿度,分析了白肋烟晾制期间晾房内外的温湿度差异,比较了加装风机循环通风对晾房温湿度的影响。结果表明,晾房内温湿度主要受外界天气的影响,但晾房可缓解外界天气的影响;晾房内温度变化与相对湿度变化呈相反趋势,温度高时相对湿度低,温度低时相对湿度高;晾房内上层温度较下层高,上层湿度较下层低。在晾房内加装风机能够调控晾房内的温湿度状况,可适度减少晾房上层与下层的温湿度差异,但是由于晾房内温湿度主要受外界气象条件影响,仅安装循环风机对降低晾房内相对湿度的效果有限。     

Compatibility and incompatibility in witloof-chicory (Cichorium intybus L.). 1. The influence of temperature and plant age on pollen germination and seed production

Summary For the production of inbred lines and F₁ hybrids in witloof-chicory information is wanted on characteristics such as the incompatibility system. These characteristics can only be studied properly if the influence of temperature and physiological status of the plant on pollen germination and seed production is known. Investigations were carried out with 9 self-incompatible (SI) and 6 self-compatible (SC) clones in glasshouses of the IVT phytotron at constant temperatures of 10, 14, 17, 20, 23 and 26°C. In general, in vivo pollen germination percentages were rather low after self pollination with an optimum for germination around 17–20°C. No seeds were formed at the lowest temperature (10°C) while seed production for SC clones was usually (rather) good at higher temperatures. At 26°C seed production in some clones decreased. Both pollen germination and seed production decreased at the end of the flowering period. There was a rather positive relationship at e.g. 17 and 20°C between pollen germination after selfing and seed production. When no pollen germination was observed, no seed formation occurred. When pollen grains did germinate, seed development would not necessarily occur in all cases. So this relationship only enables negative mass selection for SC.     

春季低温对小麦花粉育性及粒数形成的影响

小麦拔节后遭遇春季低温,每穗粒数下降,产量降低。为探明春季低温引起每穗粒数减少的生理原因,以春性小麦扬麦16和半冬性小麦徐麦30为供试品种,研究小麦倒二叶出生期(昼夜5℃/–3℃)、孕穗期(昼夜8℃/–1℃)和开花期(昼夜12℃/4℃)分别进行低温处理对小麦花粉育性及每穗粒数形成的影响。结果表明:倒二叶出生期和孕穗期低温均导致2个小麦品种在二胞花粉期和三胞花粉期花药中的多糖物质淀粉和蛋白质的代谢异常,绒毡层解体延迟;孕穗期低温还造成花粉母细胞减数分裂中染色体配对异常、出现微核等情况,影响正常雄配子体形成;花粉败育率表现为倒二叶出生期低温处理>孕穗期低温处理>开花期低温处理,徐麦30败育率高于扬麦16;3个时期低温均显著降低了2个小麦品种结实小穗数、每小穗结实粒数和每穗粒数,以倒二叶出生期低温处理穗粒数降低的幅度最大。相关分析表明,春季低温引起花粉母细胞减数分裂异常、绒毡层延迟解体、花药营养物质供给不足导致的花粉育性下降,是春季低温导致小麦每穗粒数减少的主要原因。     

Gamma-irradiation of cacao (Theobroma cacao L.) pollen: Effect on pollen grain viability,germination and mitosis and on fruit set

Summary Theobroma cacao pollen fertilization capability was studied after 0, 50, 100, 200, 500 and 1000 Gy gamma-irradiation. For all irradiation doses, no alteration of pollen grain viability and in vitro germination was observed. In situ, for all doses, pollen tubes penetrated into the styles and reached the ovules 20 hours after pollination. In vitro observations of the pollen grain nuclei after 20 hours incubation showed that pollen irradiation causes inhibition of the division of the generative nucleus. Fruit survival rate 30 days after pollination decreased as irradiation doses increased from 0 to 100 Gy, and over 100 Gy no fruit set was obtained. The possibility of using irradiated pollen as a method for obtaining haploid cacao plantlets is discussed.     

春季低温对小麦花粉育性及粒数形成的影响

Grain yield and the number of grains per ear of wheat decreased under the low temperature after jointing stage. In order to explore the physiological reasons of the decrease of grains number per ear by low temperature in spring, the spring wheat variety Yangmai 16 and the semi-winter wheat variety Xumai 30 were used as tested varieties to analyze the effects of low temperature in spring on the fertility of pollen and the formation of grain numbers at the appearance of the penultimate leaf stage (5℃/-3℃, day/night), booting stage (8℃/-1℃, day/night), and anthesis stage (12℃/4℃, day/night). The results showed that low temperature at the appearance of the penultimate leaf stage and booting stage resulted in abnormal metabolism of starch and protein in the anther both at the binuclear and tri-nuclear pollen stages and delayed degradation of the tapetum. The low temperature at the booting stage caused abnormal meiosis of pollen mother cells, abnormalities in chromosome pairing, which affected the formation of male gametophyte. The abortion rate of pollen was more significantly increased under low temperature at the appearance of the penultimate leaf stage than that at the booting stage, and it was the minimum at anthesis stage. The abortion rate of pollen in Xumai 30 was higher than that in Yangmai 16. The low temperature at three stages had significant effects on the number of spikelets, the number of fertile spikelets and the number of grains per spikelet. The effect of low temperature at the appearance of the penultimate leaf stage on grains number per spikelet was the most significant. There was a significant positive correlation between the number of grains per spike and pollen fertility, which was affected by abnormal meiosis, delayed degradation of the tapetum, and undersupply of nutriment for anther development. Therefore, the decline of pollen fertility caused by low temperature in spring is the main reason for the decrease of grains number per spike.     

Carbamate-induced flowering in asparagus (Asparagus officinalis L.) seedlings: optimization of treatment and cultivar variation in flowering response and pollen germination

Optimal carbamate treatment conditions were studied for flower induction in seedlings of an asparagus cultivar ‘Mary Washington 500 W’. Flower induction was most accelerated by soaking seeds in 50 mg l⁻¹ carbamate solution for 12 days at 25 ^°C under the fluorescent light. Longer exposure to carbamate over a 12 day period induced a higher percentage of seedlings to flower. A higher percentage of flowering seedlings were male. Flower induction frequency among seven cultivars through carbamate treatment widely ranged from 13 to 67%. ‘Geynlim’, ‘Mary Washington 500 W’ and ‘Welcome’ exhibited a high percentage of flowering seedlings, while ‘Larac’ and ‘Vulkan’ showed low values. Only male flowers were induced in all-male cultivars. Variation in pollen germination was found within all cultivars. ‘Geynlim’, ‘Cito’ and ‘Mary Washington 500 W’ showed high values of average pollen germination. Application of carbamate compound to induce flower production can rapidly produce homogenic cultivars which include both sexes. This is necessary for genetic studies and breeding purposes. This revised version was published online in August 2006 with corrections to the Cover Date.     

Pollen and pistil morphology, in vitro pollen grain germination and crossing success of Lens cultivars and species

Morphological and in vitro germination characteristics of pollen altogether with pistil and style length were analysed, so as to carry out a morphological comparison between different lentil (Lens culinaris Medik.) cultivars and wild species, as well as to correlate the morphological and functional statistics with data regarding crossing success. Pollen length and width in the different genotypes were found to have a positive and highly significant correlation with pistil and style length and in vitro pollen tube length. A cluster analysis detected two different plant groups, namely, (i) large‐seeded L. culinaris (macrosperma), and (ii) a second group formed by two subgroups, a first subgroup with L. ervoides standing alone and a second subgroup including small‐seeded L. culinaris (microsperma) and the wild L. culinaris ssp. orientalis, L. odemensis, L. nigricans. A high and significant correlation was detected between crossing success and phenotypic similarity (r > 0.98; P < 0.05), therefore implying that phenotypic similarity, based on pollen morphology and in vitro pollen length together with pistil and style length, is a good predictor of hybridization success.