A Persisting Cellulosic Wall of Microspore Mother Cells during Microsporogenesis in Allium tuberosum Rottl. and Cyclamen persicum Mill

Light microscopic studies were carried out on the anthers ofAllium tuberosum Rottl. and Cyclamen persicum Mill. Callosedeposition is initiated within the primary wall round each microsporemother cell during early prophase of meiosis I and is of maximumthickness at the tetrad stage. The original cellulosic wall,contrary to earlier reports for other species, persists aroundthe microspore mother cells until the late tetrad stage in bothspecies. In C. persicum, it dissolves to release the callose-encasedtetrads, and in A. tuberosum, il dissolves simultaneously withcallose at the time of release of microspores. Allium tuberosum Rottl., Cyclamen persicum Mill., microsporogenesis, microspore mother cell     

Anther Culture of Lolium temulentum, Festuca pratensis and Lolium x Festuca Hybrids. II. Anther and Pollen Development In Vivo and In Vitro

The various pathways of pollen development were investigatedin cultured anthers of Lolium temulentum, Festuca pratensisand the L. multiflorum x F. pratensis hybrid ‘Elmet’.In all three, development from the vegetative cell was the predominantpathway of pollen callus development. However, there were characteristicdifferences in the behaviour of the generative cell. In L. temulentumit remained attached to the pollen wall and degenerated, whereasin F. pratensis it divided. In ‘Elmet’ it detachedfrom the pollen wall and remained undivided. Both polarizedand unpolarized partitioned calluses were observed. Developmentof the fusion product of the vegetative and generative nucleiwere also observed in anthers of L. temulentum. Anomalous grainswere not found to be major source of pollen calluses. Sections of anthers of L. temulentum were used to investigatethe origin of S pollen grains, the small pale-staining grainswhich denote pollen dimorphism. Such grains form out of contactwith the tapetum and are therefore determined before or duringmeiosis (i.e. before harvest of anthers for culture). Sectionswere also used to demonstrate the influence of the durationof pretreatment on the development of the middle layer of theanther wall. Festuca pratensis, Lolium temulentum, Lolium x Festuca, anther culture, haploid, microspore, pollen     

A Comparison of Anther Tissue Development in Male Sterile Aloe vera and Male Fertile Aloe ciliaris

Cytological differences between the anther development of amale sterile and a male fertile Aloe species are used to explaininteractions between anther tissues. Some deviations in thelayers of the locule wall and the microspores of the male sterileanther are related to each other and their biological functionsare discussed. The cytological development of the male sterility,which can be observed shortly after meiosis, seems to be restrictedto the locular cavity. The tapetal development and breakdownare normal, apart from the size of some orbicules. However,the pollenkitt is not transported to the pollengrains, whichstrongly supports our theory that this process is mechanicallypollen-controlled. The development of the epidermal and endothecialcells is normal, except in a part of the anthers where thesecells do not expand, after which dehiscence is incomplete. Thelatter process is discussed in relation to the deviations insidethe locular cavity. Aloe vera (L.) Burm. fil., Aloe ciliaris Haw., Liliaceae, male sterility, tapetum, pollenkitt, endothecium, anther dehiscence     

Abortive Meiosis in Plasmodial Pollen Mother Cells of Helianthemum

The anthers of two garden varieties of Helianthemum containnot only normal pollen mother cells but also a large proportionof plasmodia with varying numbers of nuclei of varying nuclearcomplements. These abnormal cells probably resulted from a splitspindle associated with a failure of wall formation during severalpremeiotic mitoses. Chromosome pairing at meiosis is higherthan might be expected and in abnormal tissues such as theseit provides evidence for ‘somatic pairing’ havingtaken place during the premeiotic mitoses. Meiosis stops atthe end of the first division in the plasmodia and althoughit is completed in the normal pollen mother cells viable pollenis never produced.     

Effect of Water Deficit on Sporogenesis in Wheat (Triticum aestivum L.)

Plants of Triticum aestivum L., cv. Gabo, were grown in a glasshousefor 4 weeks and then transferred to a controlled environmentwith 20±1 °C temperature and 16 h photoperiod. Theywere subjected to water deficit by withholding the water supplyduring various stages of floral development, including thoseimmediately before meiosis and all stages until just after anthesis. The proportion of apparently normal florets which produced grainwas reduced when water deficit occurred during and immediatelyafter meiosis in the generative tissues. The effect of thisreduced grain set on total grain yield was partially compensatedby an increase in the weight of the remaining grains. Cross-pollinationbetween stressed and well-watered plants showed that grain setwas reduced as a direct consequence of the induction of malesterility by water stress, whereas female fertility was unaffected.A large proportion of the anthers on water-stressed plants weresmall and shrivelled, did not dehisce normally and containedpollen which was devoid of normal cytoplasmic constituents andshowed no staining reaction with triphenyl tetrazolium chloride.This effect on male fertility was not a result of desiccationof the sporogenous tissue, but an indirect outcome of the decreasein water potential elsewhere in the plant. Water stress, Triticum aestivum L., wheat, pollen, sporogenesis, grain set, male sterility     

Pollen Development in Actinidia deliciosa var. deliciosa: Histochemistry of the Microspore Mother Cell Walls

The development of the microspore mother cell walls in Actinidiadeliciosa (kiwifruit) has been studied using light and electronmicroscopy. The microspore mother cell wall is similar, histochemically,and structurally in anthers from both functionally staminateand functionally pistillate flowers. Deposition, which beginsduring early prophase I, produces an electron-dense multilaminatedwall layer (layer a) and by the end of meiosis I a thick electron-lucentlayer (layer b) to the inside of this multilayered wall. Thereasons for histochemical differences and similarities betweenthese layers are discussed. The original primary wall persistsuntil the late uninucleate microspore stage. Layer (b), whichis probably mainly callose, dissolves at the late tetrad/earlymicrospore stage while layer (a), which probably also containsother polysaccharides, persists and dissolves concurrently withthe primary wall. Actinidia deliciosa, kiwifruit, microspore mother cell wall, callose, histochemistry, light microscopy, electron microscopy, male sterility     

A comparison of in vitro flowers to in vivo flowers of haploid and diploidNicotiana tabacum L.

Thin cell layers (TCLs) were cultured from inflorescences of diploid (2n=4x=48) and haploid (2n=2x=24)Nicotiana tabacum L. "Samsun" and the subsequent flowers formed in vitro were then compared to in vivo flowers. Plants derived from TCLs possessed flowers that were typical of their seed or androgenetically-derived counterparts, whereas de novo flowers from TCLs were abnormal when compared to their counterparts. The TCLs of haploid plants produced more flower buds than diploid TCLs, and did so in a shorter period of time. In vitro flowers and anthers at both ploidy levels were considerably smaller than the in vivo flowers; in vitro flowers also had variable numbers of anthers and pistils. The embryogenic capacity of anthers taken from in vivo diploid flowers was 5 times greater than that of in vitro diploid or haploid anthers. In vivo haploid anthers produced no embryoids, whereas in vitro haploid anthers did produce embryoids. Observations of mitotic cells in root tips of plants derived from anther cultures of in vitro haploid flowers revealed a mixoploid nature. Diploid meiosis was regular and haploid meiosis was irregular regardless of the origin (in vitro or in vivo) of the flowers.Supported by state Hatch funds.     

Induction and Growth of 'Microspore-Derived' Embryos of Brassica napus ssp. oleifera

Three cultivars of spring rape (Brassica napus ssp. oleifera),Tower, Willi and Duplo, were used for a study of induction andgrowth of ‘microspore-derived’ embryos, Buds, 2.0mm in length, containing uninucleate microspores were harvestedand stored for 14 d at 4 ?C in darkness. Anthers were then removedand cultured on a liquid medium based upon that of Murashigeand Skoog and containing 8% sucrose, 0.5 mg l^–1 naphthylaceticacid and 0.05 mg l^–1 benzylaminopurine. Cultures werepre-incubated at 35 ?C for 0–3 d and then incubated at30 ?C. After a total of 42 d incubation, cultures were scoredfor the presence of macroscopic embryos (1–2 mm in length)and for the presence of anthers containing abortive embryoidswhich had not developed further. The cultivars differed greatly in terms both of the frequencyof anthers showing induced embryoids and of the final yieldof embryos. Tower showed the highest frequency of induction(maximum 38% of cultured anthers with induced embryoids) whereasthe highest yield (equivalent to 1.1 embryo per cultured anther)was obtained from anthers of the cv. Duplo after a 3 d treatmentat 35 ?C. Yields from the other cultivars were much lower andwere relatively unaffected by the 35 ?C treatment. Key words: Brassica napus, Rape, Anther culture, Pollen, Haploid     

Semi-Quantification of GAX and GA4 in Male-Sterile Anthers of Rice by Radioimmunoassay

The levels of endogenous GA, and GA₄ in the anthers of a standardcultivar and the corresponding male-sterile, single gene mutantof rice, Oryza saliva L. (Japonica), were measured by radioimmunoassayusing GA₄-specific antiserum that showed highly specific immunoreactivitywith GA, and GA₄. The levels of these GAs in the anthers ofthe male-sterile mutant were about one-fifth to one-sixth ofthose in the normal cultivar, suggesting a correlation betweenthe endogenous levels of these GAs and the male sterility. ²Present address: Department of Agricultural Chemistry, UtsunomiyaUniversity, Mine-machi 350, Utsunomiya, 321 Japan (Received August 8, 1990; Accepted March 7, 1991)     

Embryos and Plantlets from Cultured Anthers of Hybrid Grapevines

Embryos and plantlets were produced in large numbers from callusformed by cultured anthers of hybrid grapevines (Vitis viniferax Vitis rupestris). Anthers of Vitis vinifera produced smallamounts of callus or failed to grow in vitro. For embryo formationanthers containing uninucleate microspores were chilled (4 °C)for 72 h before culture with Nitsch medium containing 2, 4-D(5µM) and benzyladenine (1 µM). Highest yields ofembryos were with anthers cultured in darkness. For productionof normal plantlets embryos required chilling (4 °C) for2 weeks. Unchilled embryos produced mainly abnormal plantlets.Chilling was effective in promoting plantlet growth when appliedat any stage of embryogeny. In grapes ability to produce plantlets from cultured anthersis a genetically-determined trait and maleness, as distinctfrom hermaphroditism, may be a predisposing factor. Callus derivedfrom anthers contained both haploid and diploid cells but allplantlets produced so far are diploid. The genetic constitutionof plantlets, whether they are diploids of somatic origin ordiploids from spontaneously doubled haploid cells, is not yetknown and is being determined by standard genetic methods.     

Selection for Differing Degrees of Out-breeding in Nicotiana rustica

Initial observations on Nicotiana rustica suggested that thepercentage of seed set by outcrossing might vary considerablyin a segregating population and that this might be due to variationin the position of the stigma relative to the anthers in thecorolla-tube. This, measured as the difference in level betweenthe stigma and the ring of anthers, is termed heterostathmyand the average expression of this character could be significantlyaltered by a short programme of selection. These structuralmodifications were accompanied by developmental modificationsaffecting the timing of anther dehiscence relative to the openingof the flower. Tests indicated that these changes significantlyaffected the rate of outbreeding.     

Abnormal Sporogenesis in Wheat (Triticum aestivum L.) Induced by Short Periods of High Temperature

Plants of Triticum aestivum L. cv. Gabo, grown at 20 °C,were exposed to 30 °C for short periods during the timebetween the beginning of meiosis in the pollen mother cellsand anthesis. Plant water deficit at this temperature was avoidedby maintaining a high atmospheric relative humidity and tissuewater potential did not change. This temperature treatment appliedfor 3 days, at the time of reduction division and tetrad breakup in the male tissue, lowered grain yield through a drasticreduction in grain set, but was without effect at other stagesof development. Grain set was also reduced by exposing plantsto 30 °C for 1 day only or to a 30 °C day, 20 °Cnight (16 h photoperiod) regime for 3 days during the sensitiveperiod. A reduction in grain set did not result in a compensatoryincrease in the weight of remaining grains. The female fertility of previously heat-stressed plants wasassessed by pollinating with pollen from plants grown at a lowertemperature (20 °C). Grain set in such plants was less thanthat in plants grown at the lower temperature and hand pollinatedwith similar pollen, indicating that female fertility was reducedby high temperature. This was not the sole reason for reducedgrain set, however, as some anthers on heat-stressed plantswere small and neither extruded nor dehisced normally. Suchanthers contained pollen grains that were mostly shrivelled,had abnormal cytoplasm and showed no reaction to 2, 3, 5-triphenyltetrazolium chloride. Similar effects were also noted in pollenfrom apparently normal anthers on heat-stressed plants. Triticum aestivum, wheat, heat stress, pollen, sporogenesis, grain set, male sterility, female sterility     

Shed Pollen Culture in Hordeum vulgare

Anthers of Hordeum vulgare cv. Sabarlis at the mid-unicellularpollen stage, pretreated in the excised spike for 14 d at 7°C, dehisce within 24 h of being floated on the surfaceof liquid medium. About half the pollen (1500 grains per anther)is liberated into the medium. If the anthers are then removedand the cultures re-incubated, calluses develop from the shedpollen in high yields. At low anther densities, 10p–20(1–3 x 10⁴ grains) per ml, medium preconditioned by anthersand supplemented with m-inositol (1000 mg 1^–1) is required,but at high densities, 120 anthers (2 x 10⁵ grains) per ml,preconditioning is less important, the cultured anthers themselveshaving a sufficient conditioning influence. Large-scale dissectionof anthers can be avoided by use of drops of medium, the volumebeing increased gradually as culture proceeds. Pollen remainingin the anthers after 3 d gives rise to calluses if isolatedmechanically and cultured in the inositol medium. The use ofshed pollen is seen as particularly valuable for culture inspecies whose anthers are small, tedious to dissect out anddifficult to process without severe damage.     

Vibratory Collection of Actinidia deliciosa (Kiwifruit) Pollen

Dry, powdery pollen grains were expected from 'buzz pollinated'flower species. However, vibration of Actinidia deliciosa (kiwifruit)anthers (a buzz pollinated species) by a mechanical shaker,at similar vibrations to Bombus terrestris caused clumps ofpollen joined by small droplets of tapetal fluid to be ejected.Pollen that was largely covered with tapetal fluid could notbe removed by vibration, whereas dehydrated pollen was easilyremoved, even without vibration. The late desiccation of A.deliciosa anthers after anthesis meant that pollen removed byvibration depended on the anther maturity. The presence of thedroplets gives insects which vibrate while foraging advantagesover insects which do not. A vibration attachment on a commercialpollen harvester increased the weight of pollen collected by57% over the whole day; 91% in the afternoon.Copyright 1994,1999 Academic Press Actinidia deliciosa, Bombus spp., bumblebees, buzz pollinate, kiwifruit, pollen collection, tapetal fluid, vibration     

Morphogenic Potential of Cultured Floral Explants of Crocus sativus L. for the In Vitro Production of Saffron

Explants of immature ovaries, stigmas, anthers and petals ofCrocus sativus were cultured on White's media supplemented witheither NAA and zeatin or 2,4-D and BAP in various combinations.The formation of stigma-like structures occurred on the explantsor on the callus derived from the explants, but this was onlyobserved when NAA and zeatin were used. Formation of stigma-likestructures were observed on anthers, petals, stigmas and half-ovaries,with the best result being obtained on explants consisting ofhalf-ovaries cultured on medium containing NAA at 40 mg dm^–3and zeatin at 4.0 mg dm^–3. These stigmas developed anintense orange pigment and grew to 3.0 cm in length and hada strong saffron aroma. A preliminary comparison using thinlayer chromatography of the yellow pigments produced by thestigma-like structures grown in vitro and those grown naturallyshowed the pigment composition to be similar. Key words: Crocus sativus L., explants, NAA, zeatin, saffron     

Metabolism of Gibberellins in Cell-Free Extracts of Anthers from Normal and Dwarf Rice

Cell-free extracts were prepared from anthers of normal anddwarf rice (Oryza sativa L.), and the metabolism of radioisotope-labeledgibberellins in the extracts was analyzed by HPLC and gas chromatography-massspectrometry (GC/MS). GA₁₂ was converted to GA₁₅ and GA₃₄ inthe extracts. GA₂₀ was converted to GA¹, GA₈ and GA₂₉, but GA₉was converted only to GA₃₄. The extracts of the dwarf cultivar,Waito-C (dy mutant), showed the same 3ß-hydroxylationactivity as did those of the normal cultivar, Nihonbare, indicatingthat the dy gene is not expressed in the anthers. These resultssuggest that the regulation of the biosynthesis of gibberellinsin rice is organ-specific. (Received November 9, 1989; Accepted January 10, 1990)     

Expression of the nuclear gene TaF(A)d is under mitochondrial retrograde regulation in anthers of male sterile wheat plants with timopheevii cytoplasm

Alterations of mitochondrial-encoded subunits of the F_oF₁-ATPsynthase are frequently associated with cytoplasmic male sterility(CMS) in plants; however, little is known about the relationshipof the nuclear encoded subunits of this enzyme with CMS. Inthe present study, the full cDNA of the gene TaF_Ad that encodesthe putative F_Ad subunit of the F_oF₁-ATP synthase was isolatedfrom the wheat (Triticum aestivum) fertility restorer ‘2114’for timopheevii cytoplasm-based CMS. The deduced 238 amino acidpolypeptide is highly similar to its counterparts in dicotsand other monocots but has low homology to its mammalian equivalents.TaF_Ad is a single copy gene in wheat and maps to the short armof the group 6 chromosomes. Transient expression of the TaF_Ad–GFPfusion in onion epidermal cells demonstrated TaF_Ad's mitochondriallocation. TaF_Ad was expressed abundantly in stem, leaf, anther,and ovary tissues of 2114. Nevertheless, its expression wasrepressed in anthers of CMS plants with timopheevii cytoplasm.Genic male sterility did not affect its expression in anthers.The expression of the nuclear gene encoding the 20 kDa subunitof F_o was down-regulated in a manner similar to TaF_Ad in theT-CMS anthers while that of genes encoding the 6 kDa subunitof F_o and the subunit of F₁ was unaffected. These observationsimplied that TaF_Ad is under mitochondrial retrograde regulationin the anthers of CMS plants with timopheevii cytoplasm. Key words: CMS, F_Ad subunit, F_oF₁-ATP synthase, retrograde regulation, wheat Received 8 October 2007; Revised 9 January 2008 Accepted 28 January 2008     

A Cold-Sensitive spo14 Mutation Affecting Ascospore Formation in the Fission Yeast Schizosaccharomyces pombe

In the fission yeast Schizosaccharomyces pombe, twenty sporulation-specificgenes (spo1–spo20) have been identified and analyzed.We found that a mutation designated spo14–221 caused cold-sensitivesporulation: ascospores were formed at 30?C but not at 23?C.Nuclear staining with 4',6-diamidino-2-phenylindole revealedthat a strain with this mutation completed meiosis even at therestrictive temperature. Electron microscopy showed that assemblyof forespore membranes during meiosis II was abnormal and incompletein the mutant cultured at 23?C. Temperature-shift experimentsindicated that the cold-sensitive period began during earlymeiosis I and terminated with the end of meiosis II. These resultssuggest that the product of the spo14 gene is synthesized andexecutes its function prior to the expression of the sporulation-deficientphenotype of the mutant, prior to the formation of the abnormalforespore membrane. (Received October 5, 1989; Accepted February 28, 1990)     

Mechanism of Septum Opening in Anthers of Two-rowed Barley (Hordeum vulgare L.)

To test the hypothesis that the rapid swelling of pollen grainsdriven by potassium movement opens the septum in anthers ofpoaceous plants, we studied (1) the behaviour of pollen grainsduring unfolding of the locule and (2) the distribution of potassiumin the locule in two-rowed barley. In the first experiment,the unfolding of decapitated anthers was observed. The pollengrains paved the inner wall of the locule during the unfoldingprocess, suggesting that the pollen grains bend the locule walloutward when they adhere to the wall. In the second experiment,the distribution of potassium in transverse sections of loculesin dehisced and indehisced anthers was observed. In indehiscedanthers, potassium was detected outside the pollen grains. Incontrast, in dehisced anthers, potassium was detected insidepollen grains. This suggested potassium ions moved from theinter-pollen space (locular fluid) into the pollen grains inthe locule at the time of pollen-grain swelling. Copyright 2000Annals of Botany Company Hordeum vulgare L., locule unfolding, pollen grain swelling, potassium ion, two-rowed barley