Unusual behaviour of growing pollen tubes in the styles and ovules of Spinacia oleracea L.

Summary Pollen tubes of spinach, while growing in the styles, produce branches. In the ovules and the surrounding tissue, at later stages, they grow like fungus mycelium and ramify in all directions. Haustoria-like structures are produced from the pollen tubes near the micropyle of the ovule. These structures penetrate into integuments, nucellus and other tissues and produce branches. Several pollen tubes enter a single ovule and appear to bring about polyspermy. Though the functional significance of some of these phenomena is still speculative, it is likely that the persisting pollen tubes and haustoria may be responsible for the nourishment of the growing embryo.     

Arabinogalactan proteins may facilitate the movement of pollen tubes from the stigma to the ovules in Actinidia deliciosa and Amaranthus hypochondriacus

Sexual plant reproduction is a complex process that involves a series of interactions between the male gametophyte and the different cell types of the pistil. These interactions are believed to direct the pollen tube growth until its final target, the embryo sac. Arabinogalactan proteins are complex proteoglycans that are believed to be involved in these processes. The pistil is enriched in these highly glycosylated proteins and we provide results that show the selective presence of different AGP epitopes at the surface of the cells or in the ECM of the tissues that correspond exactly to the pollen tube growth pathway in Amaranthus hypochondriacus and Actinidia deliciosa. We also show that in Actinidia deliciosa, which is a dioecious plant with the male flowers having rudimentary ovaries where fertilization does not occur, there is no presence at all of the epitopes recognised by the monoclonal antibodies utilized in this study. This revised version was published online in July 2006 with corrections to the Cover Date.     

Elucidating the behaviour of pollen tubes in intra-and interspecific pollinations of Phaseolus vulgaris L. and P. coccineus Lam.

Summary The behaviour of pollen tubes in intra-and interspecific pollinations of P. vulgaris and P. coccineus has been examined using a combination of phase-contrast, and UV fluorescence microscopy. The results indicate that P. coccineus is self-compatible in terms of pollen tube growth, and that pollen tube inhibition is not responsible for the reciprocal differences in seed set which have been observed in crosses between these species.     

Observing pollen tubes by means of fluorescence

Summary There appears to be interest, also on the part of private breeders, in studying pollen tubes with the aid of fluorescence.The method described, which is applied in research on self- and cross-incompatibility, makes a rapid and correct interpretation possible.     

Note on visual distinction of fluorescent callose of pollen tubes and of sieve tubes in stylar tissue ofBrassica and its allies

Summary Using Martin's fluorescence technique the sieve tubes of the styles in theBrassiceae sometimes look confusingly like pollen tubes, but the two can be distinguished by relatively easy observational criteria.     

Pollen and pollination experiments. V. An empirical basis for a mentor pollen effect observed on the growth of incompatible pollen tubes in pear

Summary The self-incompatible pear cultivar Doyenne du Comice was selfed with the aid of the mentor pollen technique (self pollen mixed 1:1 with compatible pollen) and the pioneer pollen method (compatible pollen applied 14 h in advance of the self pollen). Observations on tube growth in the style showed that inviable methylated pollen was ineffective either as mentor or pioncer pollen, having no effect on the performance of the self pollen which stopped growing at about one quarter of the style from the stigma. Calculations made on the basis of the obtained data indicated that the viable untreated or irradiated pioneer and mentor pollen, the former somewhat better than the latter, aided the self pollen tubes to reach the base of the style.     

Interspecific Crossability and Inheritance in Pelargonium

Different Pelargonium hybrids are of great importance to horticulture. Breeding; for F₁ hybrid and clonal eultivars is particularly prevalent in Europe, Japan and North America. The results of a great deal of breeding research are scattered throughout different journals and published in several different languages. The aim of this review is to summarize the results of research on interspecific crosses and the inheritance of flower and leaf colour, plant habit, resistance and floret type.     

Germination of pollen of weed rye (Secale segetale L.) on wheat (Triticum aestivum L.) stigmas and the growth of the pollen tubes

Summary Two gene pairs have been found regulating the crossability of wheat and rye. It is concluded from our work that the same genes regulate crossability between wheat and weed rye. The crossing barrier was not observed in the stigma, style or ovary wall because pollen tubes of weed rye were seen in these tissues irrespective of the wheat variety used as the female parent.Pollen grains germinated within 6 min after pollination. The tubes reached the region of the micropyle after about 40 min.     

The inheritance of flower doubleness and nectary spur in Pelargonium x hortorum Bailey

Summary The formation of single flowers of 5 petals and 5 sepals is determined by the homozygous recessive state, dd, of the doubleness gene, D/d, which is epistatic to modifying genes determining flower type. In the presence of the dominant allele, i.e. genotypes DD or Dd, the flowers are semi-double or double. Owing to the D allele alone, the single frequency of 5 petals and 5 sepals is doubled to 10 petals and 10 sepals, of which up to 5 are petaloid, to give a semi-double flower. In addition, in the presence of the D allele, three modifying loci M1/m1, M2/m2, and M3/m3 are activated to give a series of distinct doubles with integral multiples of the basic perianth number. The homozygous recessive genes m1m1 and m2m2 both add an increment of 10 perianth parts, and m3m3 adds an increment of 20 perianth parts. In heterozygotes, M1m1, M2m2 and M3m3, the dominant alleles inhibit the incremental effect of their corresponding recessive alleles. The single flower cultivars investigated probably have the genotype dd, M1M1, M2M2, M3M3 and the semi-double cultivars the genotype Dd, M1m1, M2M2, M3M3.The single flowers have a nectariferous spur, characteristic of the genus, adnate to the pedicel. As the spur is absent from semi-double and double flowers, its presence is assumed to be either a pleiotropic effect of the single flower gene, or to be controlled by an unidentified gene tightly linked with it.     

The site of action of the crossability genes (Kr 1, Kr 2) between Triticum and Secale. I. Pollen germination,pollen tube growth,and number of pollen tubes

Summary Seven genotypes of common wheat (Triticum aestivum L.) were crossed with rye (Secale cereale L.) in order to find the site or sites of action of the crossability genes, Kr ₁ and Kr ₂, of wheat. The data obtained, by fluorescence microscopy, were compared to the controls (wheat x wheat). The results indicate that the crossability genes have little effect on pollen germination and on the time taken for the pollen tubes to reach the microphyle, irrespective of their crossabilities with rye. The number of pollen tubes reaching the microphyle is, however, affected by the Kr-genes, as high crossable genotypes have more pollen tubes than the low crossable ones. There was a high correlation between the mean number of pollen tubes at the micropyle with seed set, which also reflects the crossability. The Kr-genes seem to manifest themselves in the retardation and inhibition of pollen tube growth between the style base and the top of the embryo sac, where the effect is most distinct in the low crossable genotypes.     

香叶天竺葵多倍体精油的化学成分研究

探讨香叶天竺葵(Pelargonium graveolens L'He'rit)染色体加倍后精油的香气特征,为香叶新品种选育提供理论基础。对香叶天竺葵扦插苗、组培苗和多倍苗的香叶油进行GC-9A分析,并与玫瑰香叶油、法国波尔蓬香叶油的主成分进行对比。这5种油的化学成分相同,但各成分的百分含量有差异。组培苗及多倍苗香叶油中香叶醇、甲酸香叶酯、芳樟醇的含量显著提高,而香茅醇、甲酸香茅酯、玫瑰醚的含量有所下降。其中,多倍苗香叶油含：香茅醇26.1%,香叶醇14.81%,β-古芸烯4.77%,这3个主香成分接近法国波尔蓬香叶油中的含量。香叶天竺葵染色体加倍后能改善其精油的品质,其精油中香茅醇、香叶醇的含量更接近法国波尔蓬等国外香叶油中的含量。     

The interaction between compatible and self-incompatible pollen of apple and pear as influcenced by their ratio in the pollen cloud

Summary The production of self-seed was investigated in apple and pear with the aid of viable and compatible mentor/ pioneer pollen in relation to the proportion of self-imcompatible pollen present in the pollen cloud.Treatments consisted of mixtures of compatible and self-incompatible pollen at ratios of 1:1, 1:2 and 1:9 applied once or twice or followed by self-pollination. Selfing only, whether once or twice, produced virtually no fruits or seeds, while mixed pollinations did. Generally, fruit set tended to decrease and the self-seed to increase with increasing amounts of self pollen in the pollinations.The pioncer-pollen method (compatible in advance of self pollen) appeared more effective than the mentor pollen method (compatible and self pollen mixed). The use of viable instead of dead mentor/pioneer pollen causes competition for the ovules with the self pollen, but has the advantage that, in addition to some self-seed, other seeds are formed which, e.g. in apple, are necessary to keep the fruits on the tree until harvest.Fruit set was moderately reduced at ratios of compatible pollen to self pollen not exceeding 1:9 with pear and 1:5 with apple which constitute maximal ratios in practice as regards pollinator trees: trees of the main cultivar. In fruit orchards and probably in nature with other species, the interaction between compatible and self pollen may result in more self-seed, and so suggests that inbreeding played a greater part in the evolution of self-incompatible species, than the meager results of articial self-pollination imply.     

Genetical studies of fertilization in Pelargonium × Hortorum Bailey

Summary The 6×6×4 analysis of variance of the mean percentage fertilization for six variegated cultivars of Pelargonium × Hortorum Bailey, with mutant plastids in their germ layers, and for their isogenic green clones, shows highly significant differences between plastids and between female cultivars, while differences between male cultivars and the cultivar plastid interactions are much less significant. The suggestive maternal effect is not significant. The differences between cultivars and between plastids are attributed to additive effects corresponding to additive gene action. A comparison between the mean fertilization for mid-parents and their reciprocal sets of progeny shows a significant linear regression which is equated with the narrow heritability. The net fertilization achieved for each cultivar is thought to reflect small differences in the balance between the drive of pollen tubes down the style and the strength of their inhibition by already fertilized ovules.     

Induction of 2n pollen in tulips by arresting the meiotic process with nitrous oxide gas

Triploid tulips have agronomically desirable traits such as vigorous growth and large flower size, but only a portion of all cultivated tulips is triploid. To apply 2n pollen to polyploid breeding of tulips, the polyploidizing agent, nitrous oxide gas (N₂O), was applied to bulbs. In tulips, meiosis in anthers occurs inside the bulbs from mid- to late-October. When meiosis in anthers (excised from bulbs) reached metaphase I, we treated other bulbs of the same clones with N₂O for 24–48 h. Most of the treated plants produced pollen grains with a wide-ranging or bimodal size distribution, indicating a mixture of n, 2n and aneuploid pollen grains. The use of pollen containing a relatively high proportion of giant pollen grains tended to yield larger numbers of triploids in the progeny. The number of giant pollen grains could be increased when N₂O-treated pollen grains were suspended in 10% sucrose and then sieved through a nylon mesh. Very few polyploids were observed in some cross combinations, even those involving pollen with a relatively high proportion of giant grains. Even so, this low polyploid yield most likely is due to a triploid block, because the capsules obtained in the crosses of the diploid×N₂O-treated plants contained some abnormal seeds, which were mostly triploid. Embryo culture was useful in rescuing abnormal embryos. The present study reveals that 2n pollen can be produced at high frequency using N₂O during tulip breeding.     

The viability and storage of strawberry pollen

Investigations were carried out in 1990 and 1991 to estimate the pollen viability of five strawberry genotypes and their suitability for storage. Pollen viability was assessed by acetocarmine staining, in vitro germination, and in vivo assays. Pollen was stored in darkness at ?18°C for 1 year, and pollen viability was estimated every 4 months during storage. The highest percentage of stained and in vitro germinated pollen grains, respectively, was shown by fresh pollen of cv. ‘Dukat’ (91 and 45%). The lowest values of these characteristics were observed in pollen of cv. ‘Paula’ (48% and 20%, respectively). The best response to storage at ?18°C occurred in pollen of the breeding clone ‘B-302’ and the cv. ‘Redgauntlet’. ‘Paula’ pollen responded least favourably to this. Pollen of the cvs. ‘Dukaf’. ‘Senga Sengana’, and clone ‘B-302’ after storage for 4 months, still had sufficient capacity for fruit set after cross-pollinations.     

The processing of coconut pollen

Results of experiments on collection, viability testing, storage and dispatch of coconut pollen are given, and their relevance to the breeding of coconuts is briefly discussed.Pollen was obtained in large quantities following oven-drying of male flowers at 40° C. Viability decreased as drying time increased but viable grains were obtained in greater numbers after two days than after drying for a single day.Germination of pollen in vitro was better at 30° C and 35° C than at other temperatures tried; media with high gelatine concentrations (30%) seemed superior to those with less gelatine.For normal breeding purposes storage of pollen for two or three months is adequate. At low temperature, reliable storage in sealed ampoules for at least this period was obtained after further drying pollen over silica gel. Some samples retained good viability for considerably longer. Most samples stored over silica gel were still viable after 5 months, though viability was low. Over damp CaCl₂ considerable reduction in viability occurred during the first month but there was little further reduction at least up to 7 months after collection, and all samples were still viable after 18 months. Freeze-dried pollen in ampoules under vacuum had up to 40% viability after storage for one year.At room temperature, viability of pollen kept at controlled humidities over sulphuric acid solutions, though retained for longer periods than in an uncontrolled atmosphere, was only reliably maintained for about three weeks; some samples remained viable for longer periods. Freeze-drying was found to greatly increase the longevity of pollen kept at room temperature; freeze-dried pollen used in a trial shipment to New Guinea retained viability for four months and was successfully used in a number of controlled pollinations.     

红花种子发育规律及适宜采收期研究

通过对川红花种子生长发育过程中的种子鲜重、容积、干物质、含油率、发芽率的分析,研究红花种子发育规律及适宜采收期.结果表明:红花种子干物质积累可以用生长曲线拟合,方程为Y=46.10/(1+e(2.31-0.154t),R2=0.983**.于开花后29.3d达到极大值的90%以上,开花后34.5d达到极大值的95%以上,即开花后30d红花种子干物质积累基本完成.开花后30d左右为红花种子的适宜采收期.     

The production of 2n pollen in rose

Based on the size differences found between haploid and diploid pollen produced by diploid and tetraploid rose cultivars, respectively, 2n pollen producers were identified in a population of 53 diploid hybrids from a cross between a dihaploid rose, derived from the haploidization of a tetraploid modern cultivar and the diploid species R. wichuraiana. Frequency of 2n pollen producers was estimated in 2002, 2003 and 2004. Highly variable frequencies were found i) within population; ii) during years of observation (between years and between different months in the same year). The variation of 2n pollen production could be related to environmental fluctuations. A cytological analysis of male meiosis was carried out in 10 hybrids randomly chosen. Among meiotic abnormalities leading to 2n pollen formation, triads (containing a 2n microspore at one pole and two n microspores at the other) resulting from abnormal spindle geometry were frequently observed. The mode of 2n pollen formation is genetically equivalent to a First Division Restitution (FDR) mechanism. FDR 2n pollen transmits a high percentage of the heterozygosity from the diploid parent – 2n pollen producer-to the tetraploid offspring.     

The effect of pollen load and pollen grain competition on fertilization success and progeny performance inFagopyrum esculentum

Summary Flowers of cultivated buckwheat (Fagopyrum esculentum Moench) often receive natural pollen loads of fewer than 10 pollen grains. The cultivated varieties also have high genetic variability. These observations raise the question of whether seed production in buckwheat is often limited by pollen delivery, and whether small increases in pollen load could result in gametophytic selection through pollen grain competition. In greenhouse-grown buckwheat plants, embryo sac penetration by pollen tubes was universal with 10 or more pollen grains. However, seed production increased with pollen load up to 30 grains per flower. Larger pollen loads, which intensify selection among gametophytes, resulted in more vigorous progeny. Seedlings produced from high pollen load (15–20 pollen grains) were larger (40% by weight) than those from low pollen load (5 pollen grains). These results are evidence that pollen grain competition can occur in buckwheat with benefits for progeny performance.