Polyethylene glycol improves the in vitro growth of Brassica pollen tubes without loss in germination

The culture media for the in vitro pollen assay of Brassicaspecies have so far shown good percentage germination, but limitedpollen tube growth. It is reported here that by lowering sucroseconcentration from 20% to 5 or 10 % and by adding polyethyleneglycol 4000 in the culture medium, high percentage germinationand high tube growth (10 times that in the standard media) canbe achieved in three species of cultivated Brassica. This improvedmedium should be useful in fundamental and applied studies onthe pollen biology of Brassica species. Key words: Brassica, pollen, pollen germination, pollen tube growth, polyethylene glycol     

Response of in vitro pollen germination and pollen tube growth of almond (Prunus dulcis Mill.) to temperature,polyamines and polyamine synthesis inhibitor

Prunus dulcis L. ‘Mamaei’ is grown widely in souhtwest of Iran. It blooms in early spring when temperatures are still low. Based on our knowledge there are no reports in the literature regarding pollen behavior of this cultivar under specified condition. Thus, the possible factors for low germination percentage in this cultivar have not been reported. The effect of three different temperatures (10, 25, or 35 °C), polyamines (putrescine, spermidine, and spermine) and polyamine synthesis inhibitor, methylglyoxals-bis (guanyl-hydrazone) (MGBG) on in vitro pollen germination and pollen tube growth were investigated in P. dulcis L. ‘Mamaei’. All temperatures and chemicals significantly affected both pollen germination percentage and pollen tube growth. In general, different polyamines stimulated the pollen germination percentage compared to the control at all temperatures, but increasing the temperature, particularly to 35 °C, had demonstrated inhibitory effects on pollen germination. At a concentration of 0.05 mM putrescine and spermidine and 0.005 and 0.025 mM spermine revealed longer pollen tube growth than that of the control at 10 °C, while higher concentrations tended to inhibit pollen tube growth. At 25 °C, most of the treatments had an inhibitory effect on pollen tube growth except for 0.25 mM putrescine and 0.005 mM spermine, which slightly stimulated pollen tube growth. Pollen germination and pollen tube growth were inhibited by MGBG at all temperatures and in all concentrations.     

Effect of Growth Regulators and Light on Pollen Germination and Pollen Tube Growth in Pinus roxburghii Sarg

Pine (Pinus roxburghii) pollen grown in suspension cultureswas used to study the effects of growth regulators and lightconditions on germination and pollen tube growth. Indol-3-ylacetic acid, gibberellic acid, ethylene, abscisic acid and cyclicAMP (cAMP) at low concentrations (1–10 mg 1^–1) promotedgermination and tube growth. Addition of 1 and 10 mg 1^–1cAMP to any of the growth regulators had a promotory effect.Pollen tube growth decreased in white light as compared to thedark, and was increased in red light. Far-red light counteractedthe effect of red light. The effect of growth regulators incausing the enhanced tube growth appears to be manifested throughsubstances such as cAMP, and phytochrome seems to be involved. Pinus roxburghii, pine, pollen germination, pollen tube growth, growth regulators, cyclic AMP, phytochrome     

Pollen Diffusates of Crotalaria retusa and their Role in pH Regulation

Details of the release of proteins and amino acids from culturedpollen grains and the role of the leached metabolites in pollengermination, pollen tube growth and regulation of pH of theculture medium in Crotalaria retusa have been investigated.In unbuffered media, satisfactory pollen germination and tubegrowth occurred over a wide range of pH values 4.0–9.0.This was related to the ability of pollen diffusates to shiftthe pH to 6.25 in all these media. Similar pollen germinationand pH shift was observed when the pollen was eluted twice beforeculturing. When the pH shift was reduced by using buffered media,optimal germination and tube growth occurred only at pH 6.0.Pollen diffusates had a strong buffering capacity. Proteinsand amino acids released from pollen do not seem to have a directrole in pH regulation. The components involved in pH regulationmay originate from the pollen wall as well as from the cytoplasm. Crotalaria retusa L, pH regulation, pollen diffusates, pollen germination     

Influence of Temperature and Ageing of Ovules and Pollen on Reproductive Success in Trifolium repens L.

Four clones of Trifolium repens L., originating from Iceland,Denmark and Israel, were cultivated in controlled environmentchambers at 10, 14, 18 and 22°C. Seed set at 10°C was,on average, 45% lower than at 18°C. Generally, seed frequencieswere higher in the stylar ovule positions than in the basal.This polarization became more pronounced at low temperatures.At least 30% of the decrease in seed set was caused by inadequatepollen tube growth. This was further supported by in vitro studieswhich showed that pollen developed significantly shorter pollentubes at low temperatures and a strong positive correlationbetween the capacity of male parents to induce seed set in basalovule positions and the length of pollen tubes in vitro. Femaleage, determined by days relative to anthesis, was also foundto have a significant influence on seed set, i.e. when pollinationwas delayed until the fifth day of flowering, seed set decreasedby an average of 60% when compared to florets pollinated onthe first day of anthesis. Pollen age did not influence seedset. Ageing of pollen decreased in vitro germinability, tubeelongation and the percentage of pollen tubes with sperm cells.Seed set, pollen germinability, pollen tube lengths, and abilityto form sperm cells in vitro varied significantly among clones.Copyright1994, 1999 Academic Press Trifolium repens, white clover, temperature, pollen tube, sperm cells, ovule fertility, seed set     

Fruit Number in Relation to Pollen Production and Viability in Groundnut Exposed to Short Episodes of Heat Stress

Hot days and warm nights are important environmental factorslimiting fruit yields of groundnuts in the semi-arid tropics.The objective of the present research was to quantify the effectsof short episodes of heat stress on pollen production and viability,and fruit yield. Plants of cultivar ‘ICGV 86015’were grown at a day/night temperature of 28/22 °C from sowinguntil 9 d after flowering. Cohorts of plants were then exposedto a factorial combination of four day (28, 34, 42 and 48 °C)and two night (22 and 28 °C) temperatures for 6 d. Thereafter,all plants were maintained at 28/22 °C until final harvest9 d later. Number of flowers per plant (FN), the proportionof flowers setting pegs (fruit-set), the number of pegs andpods per plant (reproductive number, RN_t), pollen productionper flower and pollen viability were determined during the 6d stress period. There were strong negative linear relationsbetween day temperature over the range of 28 to 48 °C andFN (slope, -1.1 °C^-1), fruit-set (-2.8% °C^-1), RN_t(-0.90°C^-1), and pollen production (-390 °C^-1) and viability(-1.9% °C^-1). Warmer night temperature (28 vs. 22 °C)had no effect on FN, but reduced fruit-set (31 to 19%), RN_t(8to 5), and pollen production (4389 to 2800) and viability (49to 40%). There were no significant interactions between dayand night temperature. Reduced fruit-set was a consequence offewer pollen grains and reduced pollen viability. The thresholdday temperature for pollen production and viability was 34 °Cand there were strong negative linear relations between bothpollen production and pollen viability and accumulated temperature>34 °C. Copyright 1999 Annals of Botany Company Arachis hypogaea L., fruit-set, groundnut, heat-stress, peanut, pollen viability, pollen production, temperature.     

Stigma-surface Esterase Activity and Stigma Receptivity in Some Taxa Characterized by Wet Stigmas

Stigma-surface esterase activity and stigma receptivity througha sequence of developmental stages of the pistil have been studiedin four taxa characterized by having wet stigmas — Petuniahybrida, Nicotiana tabacum, Crinum defixum and Amaryllis vittata.The style is solid in the first two and hollow in the lattertwo taxa. In all the taxa, stigma—surface esterase couldbe detected in a thin surface layer (pellicle) from a very earlystage of pistil development, irrespective of the presence orabsence of the exudate. However, the taxa showed variation instigma receptivity. In Petunia and Nicotiana, stigmas from pistilsof all the stages supported pollen germination and tube growth.In Amaryllis and Crinum, stigmas of only the mature pistils,when the exudate is present on the stigma, supported normalpollen germination and tube growth. It is inferred that in taxacharacterized by a wet stigma and solid style, the factors requiredfor pollen germination are present from an early stage of pistildevelopment and the exudate per se is not involved in pollengermination. In taxa characterized by a wet stigma and hollowstyle, however, the pellicle does not carry the factors requiredfor pollen germination and tube growth; they appear to be presentin the exudate. Petunia hybrida Vilm, Nicotiana tabacum L., Crinum defixum, Ker-Gawl, Amaryllis vittata Ait., tobacco, pollination, pollen germination, stigmatic exudate, stigma receptivity, stigma-surface esterase, esterase activity     

Influence of temperature on the in vitro pollen germination and pollen tube growth of various native Iranian almonds (Prunus L. spp.) species

Pollen germination and pollen tube growth was quantified among various native Iranian wild almonds (P. dulcis (Mill.) D. A. Webb, P. eleaegnifolia Mill., P. orientalis Mill., P. lycioides Spach, P. reuteri Bioss. et Bushe, P. arabica Olivier, P. glauca Browick and P. scoparia Spach in order to identify differences in the tolerance of pollen to temperature variations. Pollen germination and pollen tube growth were observed after incubation in darkness in a germination medium for 24?h at 10?C50°C at 5°C intervals. Maximum pollen germination of the wild almond species and specify that 60% was obtained for P. orientalis pollen and 98% for P. scoparia. Pollen tube length ranged from 860???m was obtained in P. lycioides and 1490???m in P. scoparia. A modified bilinear model best described the response to temperature of pollen germination and pollen tube length. Almond species variation was found for cardinal temperatures (T _min, T _opt and T _max) of pollen germination percentage and pollen tube growth. Mean cardinal temperatures averaged over eight almond species were 14.7, 24.2, and 43.7°C for maximum percentage pollen germination and 14.48, 25.3, and 44.4 °C for maximum pollen tube length. The principal component analysis (PCA) identified maximum percentage pollen germination and pollen tube length of the species, and T _max for the two processes as the most important pollen parameters in describing a species tolerance to high temperature. PCA also classified Prunus L. spp. into four groups according to the tolerance of pollen to temperature variations. The T _min and T _opt for pollen germination and tube growth, rate of pollen tube growth were less predictive in discriminating species for high temperature tolerance.     

Response of in vitro pollen germination and pollen tube growth of groundnut (Arachis hypogaea L.) genotypes to temperature

Air temperatures of greater than 35 °C are frequently encountered in groundnut‐growing regions, especially in the semi‐arid tropics. Such extreme temperatures are likely to increase in frequency under future predicted climates. High air temperatures result in failure of peg and pod set due to lower pollen viability. The response of pollen germination and pollen tube growth to temperature was quantified in order to identify differences in pollen tolerance to temperature among 21 groundnut genotypes. Plants were grown from sowing to harvest in a poly‐tunnel under an optimum temperature of 28/22 °C (day/night). Pollen was collected at anther dehiscence and was exposed to temperatures from 10° to 47·5 °C at 2·5 °C intervals. The results showed that a modified bilinear model most accurately described the response to temperature of percentage pollen germination and maximum pollen tube length. Genotypes were found to range from most tolerant to most susceptible based on both pollen characters and membrane thermostability. Mean cardinal temperatures (T_min, T_opt and T_max) averaged over 21 genotypes were 14·1, 30·1 and 43·0 °C for percentage pollen germination and 14·6, 34·4 and 43·4 °C for maximum pollen tube length. The genotypes 55‐437, ICG 1236, TMV 2 and ICGS 11 can be grouped as tolerant to high temperature and genotypes Kadiri 3, ICGV 92116 and ICGV 92118 as susceptible genotypes, based on the cardinal temperatures. The principal component analysis identified maximum percentage pollen germination and pollen tube length of the genotypes, and T_max for the two processes as the most important pollen parameters in describing a genotypic tolerance to high temperature. The T_min and T_opt for pollen germination and tube growth, rate of pollen tube growth were less predictive in discriminating genotypes for high temperature tolerance. Genotypic differences in heat tolerance‐based on pollen response were poorly related (R² = 0·334, P = 0·006) to relative injury as determined by membrane thermostability.     

In vitro pollen competitive ability in Viola tricolor: temperature and pollen donor effects

In this study on Viola tricolor pollen, the competitive ability of 16 pollen donors originating from a wild population was analysed in a set of greenhouse and germination temperatures. The aim was to examine the consistency in donor pollen performance across temperatures and to see whether variation in performance was random or due to individual differences in the plastic response to temperature. Pollen tube growth rate in vitro was investigated in two greenhouse temperatures (on the day pollen was collected) and in four germination temperatures. In addition, pollen tube growth rate was assessed in vivo (in one temperature) to examine the relationship between in vivo and in vitro growth. A temperature difference of 5 K - corresponding to natural variation in time and space detected in the field - affected pollen tube growth rate. For both temperature components, significant pollen donor by temperature interactions were found and rank order of pollen donors changed across treatments. Although pollen competitive ability in violets was strongly influenced by both temperature components, the occurrence of pollen donor by temperature interactions indicates that donor siring ability varies with temperature. This, in turn, may suggest a means to maintain pollen competitive ability despite selection for this trait.     

Computer-assisted Video Image Analysis of Spatial Variations in Membrane-associated Ca2+ and Calmodulin during Pollen Hydration, Germination and Tip Growth in Nicotiana tabacum L.

Video images of the distributional pattern of membrane-associatedcalcium (Ca²⁺) and calmodulin (CaM) have been documented andanalysed during pollen hydration, germination and tip growthin Nicotiana tabacum. Digitization of fluorescence microscopeimages of chlorotetracycline (CTC) and fluphenazine (FPZ)-fluorescenceemissions reveal that there is a maximum concentration of membrane-associatedCa²⁺ and also CaM in the vicinity of germination apertures ofhydrated pollen. With the onset of germination relatively higheramounts of Ca²⁺ and CaM were found to regionalize towards theaperture through which the pollen tube would emerge Both shortand long growing pollen tubes manifest tip-to-base Ca²⁺ andCaM gradients which are disturbed in non-growing tubes. Tubegrowth and the Ca²⁺-gradient were significantly affected byvanadate and verapamil suggesting that both a vanadate-sensitiveCa²⁺-transport system and verapamil-sensitive Ca²⁺ channelsare involved in maintaining Ca²⁺ homeostasis during pollen germinationand tube growth. The possible interactions of Ca²⁺ and CaM withdifferent cytoskeletal proteins modulating organelle movementare also briefly discussed. Image analysis, calcium, calmodulin, Nicotiana tabacum L., pollen germination, pollen tube, tip growth, Ca²⁺-channels, Ca²⁺ transport ATPase     

STAMINATE BLOOM DATE AND TEMPERATURE RESPONSES OF POLLEN GERMINATION AND TUBE GROWTH IN TWO WALNUT (JUGLANS) SPECIES

Pollen was collected from ten cultivars of Juglans regia and three cultivars of the later-blooming species, J. nigra. Extensive phenological data were available for these cultivars. Cultivars were chosen on the basis of staminate bloom date to include the earliest and latest blooming individuals available and a representative range throughout the bloom season. Mean staminate bloom dates for the cultivars examined covered a period of 46 days over which time mean daily temperatures rose 6 C. In order to determine if adaptations to temperature were expressed by the gametophyte generation, pollen was subjected to controlled temperatures from 5 to 40 C in 2 to 4 C increments and analyzed for germination percentages and pollen tube elongation. A positive relationship was found for pollen germination percentage and mean staminate bloom date such that earlier blooming individuals showed lower minimum temperature thresholds for germination, and optimum temperature for pollen germination was positively correlated with mean staminate bloom date. Differences in pollen tube growth, determined separately from hydration and germination responses, were less clear. Most J. regia clones had lower minium temperature thresholds for growth than the J. nigra clones, but there was no clear relationship to earliness of bloom within the species. No differences were discerned in optimum temperatures for pollen tube growth either between the two species or within species.     

Pollen Tube Development and Characteristics of the Protein Emission in Conifers

When ripe, viable pollen of Pinus contorta, Pinus nigra, Piceasitchensis, Abies alba and Cedrus deodara is germinated on asuitable artificial substrate, the process of pollen tube growthbegins 12–36 h later, according to the species. The tubeemerges at the leptoma, a structurally specialized site in thepollen wall, and the early tube wall is continuous with thetwo microfibrillar intine strata within the grain. Later inpollen tube development, when cytoplasmic zonation has beenestablished, only the inner of these two wall layers is differentiated. Cytochemical methods show that, during hydration and throughoutthe period of tube growth in culture, proteins are releasedfrom the pollen grains; before germination most conspicuouslyfrom the leptoma, subsequently from the tube itself. The emissioncontains a number of hydrolytic enzymes and a non-catalyticmoiety. Gel-electrofocusing reveals that the hydrolases releasedfrom germinating Pinus contorta pollen include several acidphosphatase and esterase isozymes, and that there are differencesbetween the composition of the emission and the spectrum ofsoluble proteins extracted from the pollen grains before germination.Analysis by immunodiffusion demonstrates that two componentswith antigenic characteristics present in the quiescent pollengrains are represented in the emission. The possible utilityof the released components in the biology of conifer reproductionis discussed. Pinus contorta, Pinus nigra, Picea sitchensis, Abies alba, Cedrus deodara, lodgepole pine, Austrian pine, Sitka spruce, European silver fir, deodar, pollen tube, pollen germination, protein release, isoelectric focusing     

Effect of Spermidine and Methylglyoxal-bis (Guanyl-hydrazone) (MGBG) on In Vitro Pollen Germination and Tube Growth in Catharanthus roseus

Incorporation of polyamine-spermidine into the nutrient mediumat 10^–6 and 10^–5 M concentrations stimulates pollen-tubegrowth in vitro in Catharanthus roseus L. G. Don. MGBG, an inhibitorof spermidine biosynthesis, at 0.5 x 10^–3 and 1 x 10^–3M concentrations reduced the percentage of germination as wellas tube growth and at a concentration of 1.5 x 10^–3 Mgermination was totally inhibited. Pollen grains incubated inthe medium containing 1.5 x 10^–3 M MGBG, when transferredto a fresh medium with 10^–5 M spermidine, resulted in80% germination recovery, along with considerable tube growth.Experiments with actinomycin-D indicate that stimulation ofpollen-tube growth by spermidine may involve de novo synthesisof protein. Catharanthus roseus, pollen germination, tube growth, spermidine, MGBG, inhibition, actinomycin-D     

In vitro pollen germination and pollen tube growth differences among Quercus robur L. clones in response to meteorological conditions

The impact of meteorological conditions on in vitro pollen germination and pollen tube growth during the initial phases of the development of male flowers in the Pedunculate Oak, Quercus robur, is studied. Phenological observations of male flowers and pollen sampling were performed on the field trial established with grafted Pedunculate Oak clones. During the investigation, weather conditions (absolute minimum and maximum daily air temperature, minimum absolute relative humidity of air and amount of precipitation) were recorded by an automatic meteorological station installed at the field trial. Influence of meteorological conditions on pollen germination and pollen tube growth was studied in the following stages of male flower: (I) during the last ten days of flower bud dormancy, (II) during swelling of the buds, (III) during bud burst and beginning of male catkins elongation, (IV) during the final stage of male flower catkins elongation. High temperatures and low relative air humidity during the bud burst and beginning of the male catkins elongation reduced pollen germination and pollen tube growth. Weather conditions did not significantly affect pollen germination and pollen tube growth during the swelling of flower buds, or in the final stage of male catkins elongation.     

Fast loading ester fluorescent Ca<Superscript>2+</Superscript> and pH indicators into pollen of <Emphasis Type="Italic">Pyrus pyrifolia</Emphasis>

Loading of Ca²⁺-sensitive fluorescent probes into plant cells is an essential step to measure activities of free Ca²⁺ ions in cytoplasm with a fluorescent imaging technique. Fluo-3 is one of the most suitable Ca²⁺ indicators for CLSM. We loaded pollen with fluo-3/AM at three different temperatures. Fluo-3/AM was successfully loaded into pollen at both low (4°C) and high (37°C) temperatures. However, high loading temperature was best suited for pollen, because germination rate of pollen and growth of pollen tubes were relatively little impaired and loading time was shortened. Moreover, Ca²⁺ distribution increased in the three apertures of pollen after hydration and showed a Ca²⁺ gradient, similar to the tip of growing pollen tubes. The same protocol can be used with the AM-forms of other fluorescent dyes for effective labeling. When loading BCECF-AM into pollen at high temperature, the pollen did not show a pH gradient after hydration. Ca²⁺ activities and fluxes had the same periodicity as pollen germination, but pH did not show the same phase and mostly lagged behind. However, the clear zone was alkaline when pollen tube growth was slowed or stopped and turned acidic when growth recovered. It is likely that apical pH_i regulated pollen tube growth.     

Diurnal pollen tube growth rate is slowed by high temperature in field-grown Gossypium hirsutum pistils

For Gossypium hirsutum pollination, germination, and pollen tube growth must occur in a highly concerted fashion on the day of flowering for fertilization to occur. Because reproductive success could be influenced by the photosynthetic activity of major source leaves, we hypothesized that increased temperatures under field conditions would limit fertilization by inhibiting diurnal pollen tube growth through the style and decreasing subtending leaf photosynthesis. To address this hypothesis, G. hirsutum seeds were sown on different dates to obtain flowers exposed to contrasting ambient temperatures while at the same developmental stage (node 8 above the cotyledons). Collection and measurement were conducted at 06:00, 09:00, 12:00, 15:00, and 18:00 h on August 4 (34.6 °C maximum air temperature) and 14, 2009 (29.9 °C maximum air temperature). Microclimate measurements included photosynthetically active radiation, relative humidity, and air temperature. Pistil measurements included pistil surface temperature, pollen germination, pollen tube growth through the style, fertilization efficiency, fertilized ovule number, and total number of ovules per ovary. Subtending leaf measurements included leaf temperature, photosynthesis, and stomatal conductance. Under high temperatures the first measurable pollen tube growth through the style was observed earlier in the day (12:00 h) than under cooler conditions (15:00 h). Also, high temperature resulted in slower pollen tube growth through the style (2.05 mm h⁻¹) relative to cooler conditions (3.35 mm h⁻¹), but there were no differences in fertilization efficiency, number of fertilized ovules, or ovule number. There was no effect of sampling date on diurnal photosynthetic patterns, where the maximum photosynthetic rate was observed at 12:00 h on both dates. It is concluded that, of the measured physiological and reproductive processes, pollen tube growth rate showed the greatest sensitivity to high temperature under field conditions.     

RNA and Protein Synthesis in Germinating Pine Pollen

The results of autoradiographic experiments demonstrate that,as with the pollen of most other species, both the generativeand vegetative nuclei of Loblolly Pine (Pinus taeda) activelyengage in RNA synthesis from the very early stages of pollengermination. Unlike most other species, however, this newlysynthesized RNA includes rRNA. Evidence is provided for theimportance of this newly synthesized RNA in the process of continuedpollen tube growth. One and two-dimensional gel electrophoretic analysis revealsa number of both qualitative and quantitative differences amongthe proteins synthesized during the early stages of germinationand the later stages of pollen tube growth. One of the mostnotable of these is a 36 kD protein, the synthesis of whichpredominates during the later stages of pollen germination.A similar pattern of 36 kD protein synthesis is observed whenmRNA extracted from pollen at each of these stages is translatedin vitro. Key words: Pinus, pollen tube growth     

Physiology of Post-Pollination Exudate Production in Acacia

Marginson, R., Sedgley, M. and Knox, R. B. 1985. Physiologyof post-pollination exudate production in Acacia—J. exp.Bot. 36: 1660–1668. Stigmas of A. wattsiana produced 1260 nl of secretion by 90min after pollination. The optimum temperature for post-pollinationsecretion in A. baileyana, A. brownii and A. iteaphylla was20°C. Both self and cross intraspecific, interspecific andintergeneric pollinations produced a similar positive responsein A. iteaphylla and A. baileyana. In all cases aged pollenwas as effective as fresh pollen despite reduced fluorescencein the fluorescein diacetate test. Live yeast cells, fixed chickenerythrocytes, glass beads, talc and Biogel P150 did not stimulatesecretion, nor did pollen which had been washed in water orethanol despite high retention of viability in some cases Pollendiffusates dried on to glass beads produced a positive responsein A. iteaphylla and A. gracifolia. Intraspecific and interspecificpollinations involving fresh Acacia pollen resulted in pollengermination on the stigma and pollen tube growth in the styleof A. iteaphylla and A. baileyana. In contrast washed pollenfailed to germinate and pollen germination and tube growth werereduced at 35 °C as compared with 20 °C. Key words: Acacia, pollination, secretion     

Effects of genotype and temperature on pollen tube growth in perennial ryegrass (Lolium perenne L.)

Summary Low yield in seed crops of perennial ryegrass is related to low fertilization efficiency and low temperature during anthesis. To study the effect of genotype and temperature on pollen performance, we conducted greenhouse experiments at controlled temperatures. Individual florets of four genotypes that are known to differ in seed production were hand pollinated at four temperatures (14°, 18°, 22°, 26° C) both in vivo and via a semiin-vitro method involving excised florets on agar. Pollen germination and tube growth were determined with UV-fluorescence microscopy and scored in six classes at 2 h after pollination in vitro and after 0.5, 2 and 5 h in vivo. In vitro, both genotype and temperature had a significant effect on the performance of self-pollen. Pollen tube growth increased with temperature. In cross-pollinations, the pistil parent had a significant effect on pollen tube growth, and there was also a significant pistil-by-temperature interaction. In vivo, genotype and temperature significantly affected pollen performance. The genotype-by-temperature interaction was only significant 5 h after pollination. One genotype with low seed yield was pseudoself-compatible and was a relatively poor mother after cross-pollination. The effects of genotype and temperature on the growth of self-pollen might be exploited in a breeding programme.A.G. Stephenson was on a sabbattical leave at SVP in 1987