Effects of salt stress on the reproductive biology of the halophyte <Emphasis Type="Italic">Plantago crassifolia</Emphasis>

Floral phenology, pollen quality and seed set of Plantago crassifolia plants, grown in the presence of increasing NaCl concentrations, were studied to test how this Mediterranean halophyte responded to salt stress during the reproductive phase of its life cycle. Reproductive success was maximal in plants grown in non-saline conditions, or in the presence of 100 mM NaCl, but it was negatively affected by higher salinities, due to a progressive reduction of pollen fertility, seed set, and seed viability.     

Grain set failure in boron deficient wheat

Effects of boron (B) deficiency on reproductive development and grain set in wheat was studied in experiments in a sand culture in which grain set was increased by increasing B supply in the nutrient solution. Early vegetative response was also studied in a solution culture experiment with 5 M B and without added B. Effects of B deficiency on the male and female part of the wheat flower were studied in a cross fertilization experiment involving B deficient and B sufficient wheat plants. An international trial (the Boron Probe Nursery) was conducted as a collaboration between Chiang Mai University, CIMMYT and National Agricultural Research Systems in various countries, to verify the B response in non-traditional, warm wheat-growing areas.There was a wide genotypic variation in reproductive responses to B among the eight wheat genotypes studied. In sand culture with low B (0.2 M), grain set index ranged from 9.5% in SW41 to 94.5% in Fang 60; with high B (10 M) it was 90% in all genotypes. Early vegetative response to B was measured in the length of the youngest emerged blade at 12 days after sowing. Without added B the length of the leaf blade relative to that with 5 M B ranged from 0.82 to 0.92. This indicates some variation in vegetative response to B among the genotpes. However, there was no relationship between vegetative and reproductive responses to B of the wheat genotypes.Fertility of both the male and female part of the wheat flower appears to be affected by B deficiency. Ears from B deficient plants that were bagged to prevent cross fertilization set no grain. Cross pollination of B deficient female flowers with pollen from B sufficient plants resulted in only 28% grain set, compared with 94% percent from manual crossing of B sufficient pollen on B sufficient female.Reponses to B application of SW41 and other sensitive genotypes at field sites of the first international Boron Probe Nursery (1990/91) confirmed that B deficiency can be a major cause of grain set failure in wheat in warm areas.     

Two methods of haploidization in pear,Pyrus communis L.: greenhouse seedling selection and in situ parthenogenesis induced by irradiated pollen

Seedlings of 12 crosses involving pear varieties or hybrids were observed for the presence of haploid plants. On the basis of phenotypic characteristics, 17 plants corresponded to the haploid condition and, of these, 12 were determined by chromosome counting to be haploid (2n=x=17). In addition, and in order to induce in situ parthenogenesis, several pear varieties were pollinated with a selected clone carrying a homozygous dominant marker gene for the colour of red. This pollen had previously been irradiated with -rays of cobalt 60 at 0, 200, 250 and 500 Grays. The immature embryos were cultured in vitro, whereby 1 haploid and two mixoploid plants were obtained. Numerous diploid plants with the maternal phenotype were also obtained, and their genetic origin was subsequently studied by means of isozyme analysis.     

Regulation of Inflorescence Branch Development in Rice Through a Novel Pathway Involving the Pentatricopeptide Repeat Protein sped1-D

Panicle type has a direct bearing on rice yield. Here, we characterized a rice clustered-spikelet mutant, sped1-D, with shortened pedicels and/or secondary branches, which exhibits decreased pollen fertility. We cloned sped1-D and found that it encodes a pentatricopeptide repeat protein. We investigated the global expression profiles of wild-type, 9311, and sped1-D plants using Illumina RNA sequencing. The expression of several GID1L2 family members was downregulated in the sped1-D mutant, suggesting that the gibberellin (GA) pathway is involved in the elongation of pedicels and/or secondary branches. When we overexpressed one GID1L2, {"type":"entrez-nucleotide","attrs":{"text":"AK070299","term_id":"32980323","term_text":"AK070299"}}AK070299, in sped1-D plants, the panicle phenotype was restored to varying degrees. In addition, we analyzed the expression of genes that function in floral meristems and found that RFL and WOX3 were severely downregulated in sped1-D. These results suggest that sped1-D may prompt the shortening of pedicels and secondary branches by blocking the action of GID1L2, RFL, and Wox3. Moreover, overexpression of sped1-D in Arabidopsis resulted in the shortening of pedicels and clusters of siliques, which indicates that the function of sped1-D is highly conserved in monocotyledonous and dicotyledonous plants.     

Heterospecific pollen transfer from an exotic plant to native plants: assessing reproductive consequences in an Andean grassland

Background: The presence of exotic plants increases the heterospecific pollen (HP hereafter) received by native plants and reduces their reproductive output.

Aims: We assessed whether the exotic herb Echium vulgare (Boraginaceae) increased HP and reduced seed output of the native plants Phacelia secunda (Boraginaceae) and Stachys albicaulis (Lamiaceae) in an Andean locality, central Chile.

Methods: The presence of HP was studied in native plants growing with and without co-existence with the exotic E. vulgare. A complementary hand pollination experiment was carried out to assess whether E. vulgare pollen reduced the reproductive success of native plants.

Results: In the presence of E. vulgare, 17.3% and 3.7% of P. secunda and S. albicaulis individuals that coexisted with the exotic species received HP. For P. secunda, the number of conspecific pollen grains decreased in invaded patches compared with non-invaded patches; no differences were observed for S. albicaulis. The pollen of E. vulgare negatively affected the reproductive success of S. albicaulis but not that of P. secunda.

Conclusions: The presence of HP cannot be predicted from the presence of exotic plants alone, and other factors, such as flower morphology, could explain the greater HP transfer in P. secunda (actinomorphic flowers) than in S. albicaulis (zygomorphic flowers). A higher negative effect of E. vulgare pollen on P. secunda versus S. albicaulis could be related to the phylogenetic resemblance between the exotic donor and native recipient plant because pollen-stigma compatibility may be evolutionary conserved through common lineages.     

Wide hybridization in okra

Summary Crosses were made between members of the two West African okra types Soudanien and Guineen. All crosses succeeded in both directions and the F₁ plants which showed hybrid vigour for plant stature were partially sterile. Cytological observations of the F₁ plants revealed abnormal meiosis which resulted in the production of microspores of variable sizes. The frequency of viable pollen (as indicated by acetocarmine staining) was low in the hybrids: 35.80% (U.I.92× U.I.313) and 39.41% (1bk-1×U.I.215). The number of seeds produced per fruit was low in the hybrids and only a few of these seeds are viable. The possibility of gene transfer between the two okra types was discussed.     

Among-species differences in pollen quality and quantity limitation: implications for endemics in biodiverse hotspots

Background and Aims

Insufficient pollination is a function of quantity and quality of pollen receipt, and the relative contribution of each to pollen limitation may vary with intrinsic plant traits and extrinsic ecological properties. Community-level studies are essential to evaluate variation across species in quality limitation under common ecological conditions. This study examined whether endemic species are more limited by pollen quantity or quality than non-endemic co-flowering species in three endemic-rich plant communities located in biodiversity hotspots of different continents (Andalusia, California and Yucatan).

Methods

Natural variations in pollen receipt and pollen tube formation were analysed for 20 insect-pollinated plants. Endemic and non-endemic species that co-flowered were paired in order to estimate and compare the quantity and quality components of pre-zygotic pollination success, obtained through piecewise regression analysis of the relationship between pollen grains and pollen tubes of naturally pollinated wilted flowers.

Key Results

Pollen tubes did not frequently exceed the number of ovules per flower. Only the combination of abundant and good quality pollen and a low number of ovules per flower conferred relief from pre-zygotic pollen limitation in the three stochastic pollination environments studied. Quality of pollen receipt was found to be as variable as quantity among study species. The relative pollination success of endemic and non-endemic species, and its quantity and quality components, was community dependent.

Conclusions

Assessing both quality and quantity of pollen receipt is key to determining the ovule fertilization potential of both endemic and widespread plants in biodiverse hotspot regions. Large natural variation among flowers of the same species in the two components and pollen tube formation deserves further analysis in order to estimate the environmental, phenotypic and intraindividual sources of variation that may affect how plants evolve to overcome this limitation in different communities worldwide.     

The ecology and evolution of pollen odors

The literature is reviewed and new evidence presented that pollen produces odors, which serve multiple functions in pollination and defense. Pollen odor, which originates from pollenkitt, comprises volatiles that belong to the same chemical classes found in flower scents, that are in species-specific mixtures, and that contrast with odors of other floral parts. Pollen can also take up volatiles from surrounding floral odors, but this adsorption is selective and varies among species. Pollen odors are more pronounced in insect- than bird- or wind-pollinated plants, suggesting that volatile emission evolved in part under selection to attract pollinators. Pollen-feeding insects can perceive pollen odor and use it to discriminate between different pollen types and host plants. Pollen odor influences bee foraging, including the location of pollen sources, discrimination of flowers with different amounts of pollen, and hostplant recognition by pollen-specialist species. In the few wind-pollinated plants studied, odors of male flowers or pollen are comparatively high in -methyl alcohols and ketones; these volatiles may serve in pollen defense, with some known to repel insects. Pollen odor often includes chemicals with documented defense activity, which is probably aimed mainly at nonpollinator pollen-feeding insects and pathogens; an involvement in pollen allelopathy is also possible. Pollen volatiles comprise chemically diverse compounds that may play multiple roles, and their emission in pollen odor undoubtedly evolved under the principle, and often conflicting, selective pressures to both protect the male gametophyte and increase its dispersal by animals.     

Selection of embryogenic pollen from cold-treated buds ofNicotiana tabacum var. badischer burley and their development into embryos in cultures

Summary By using density gradient centrifugation, employing 55% percoll and 4% sucrose as suspension medium, it is possible to select embryogenic pollen from buds after cold treatment at 10 °C for 8 or more days. These buds at the uninucleate stage of pollen were collected from plants grown in 8 hours photocycles at 18 °C and supplied with mineral salts. The embryogenic pollen are small, starch-free with a clear cytoplasm whereas large starch-filled ones are nonembryogenic. The embryogenic pollen regularly form embryos at a frequency of 2% on a mineral medium supplemented with glutamine, asparagine and sucrose at pH 6.5.These results demonstrate, for the first time, that it is possible to have embryos in appreciable frequencies in ab initio pollen cultures raised from cold treated anthers.On leave from University of Delhi.     

Breeding systems in thePolemoniaceae

Pollen — ovule ratios and percentages of stigmatic pollen germination (SPG) were measured for over 160 taxa of thePolemoniaceae. When related to taxa with known breeding systems, it is found that low SPGs and high P:O ratios characterize xenogamous plants, high SPGs and low P:Os characterize autogamous plants. There is a significant negative correlation between P:O ratio and SPG in the whole family as well as in certain genera. Both measures can serve as reliable indicators of the breeding systems in taxa of thePolemoniaceae and can be measured in dried or living specimens. Accordingly, most polemons feature mixed breeding system, i.e. facultative xenogamy or facultative autogamy. Xenogamy is common among the tropical genera and in theLeptodactylon, Phlox andPolemonium. Autogamy is more frequent in the tribeGilieae (particularly inGilia) than in the other tribes. Annual taxa tend to be autogamous, showing on the average higher SPG and lower P:O ratio. The lepidopteran-pollinated group of species have a higher mean P:O ratio and lower mean SPG thus indicating that such plants are associated with crosspollination more than the others.     

Pollen tube growth following compatible and incompatible intraspecific pollinations in Petunia hybrida

The observation that both compatible and incompatible pollen tubes grow at identical speeds on the stigma in many plants with gametophytically controlled self-incompatibility (SI) systems has, in Petunia, been extended to cover all other facets of pollen behaviour on this tissue. On entry into the stylar transmitting tissue both types of tubes accelerate, but the compatible achieve a higher terminal velocity than do the incompatible, which eventually slow and stop. Grafting experiments show that the top 1 mm of the stylar tissue can play an important rôle in determining the future development of the pollen tube. Following mixed pollinations, proportionally too many compatible pollen tubes reach the ovary than would be expected from the results of pure compatible and incompatible pollinations indicating that incompatible pollen in some way helps prime the style for growth of compatible pollen tubes. This data is considered in terms of recent structural studies of these tissues, and related to the pollination conditions pertaining to Petunia populations in the field.Abbreviation SI self-incompatibility     

Variation in structural gender in the hermaphrodite Helleborus foetidus (Ranunculaceae): within- and among-population patterns

In hermaphrodite plants, variations in structural gender (defined as the ratio between male and female gametes) may occur at different levels (among flowers, plants, and populations). In this study, we investigated variation in four traits influencing structural gender (number of carpels, ovules per carpel, stamens, and pollen grains per stamen) within and among six distant populations of the hermaphrodite perennial herb Helleborus foetidus (Ranunculaceae) in the Iberian Peninsula. Our results show that the four traits investigated varied significantly at all levels considered. Traits influencing the female sexual component (number of carpels and ovules per carpel) showed greater variation at the lowermost levels (within flower and plant) than traits influencing the male component, which in turn varied more markedly among populations. Number of carpels per flower and number of pollen grains per anther were the most important traits affecting between-plant variation in structural gender. There was no evidence of significant plant-level trade-offs or correlations between the various male and female traits, which covaried differently across populations. The observed between-population variation in structural gender of Helleborus foetidus can be explained as a consequence of differences in self-pollination levels related to a flowers mating environment.     

Callus formation and plant regeneration through direct culture of isolated pollen of Hordeum vulgare cv. ‘Sabarlis’

Summary Pollen calli and plantlets of Hordeum vulgare cv. Sabarlis were obtained through direct pollen culture without pretreatment of spikes or preculture of anthers. Isolated immature pollen grains were cultured first in a 0.3 M mannitol solution or a C1 basal medium (Chen et al. 1979) supplemented with 0.3 M mannitol but without sucrose for 5–7 days, then transferred into a C1 medium containing 6% sucrose, 3 mM glutamine and 5 mM m-inositol. After a 3 week culture period small pollen calli derived from the pollen grains were transferred into a growth medium comprising C1 basal medium supplemented with 250 mg/1 lactalbumin hydrolysate and 0.5 mg/1 kinetin. For shoot regeneration, vigorously growing calli were transferred onto agarsolidified MS medium (Murashige and Skoog 1962) containing 3% sucrose, 2 mg/1 benzyladenine and 0.5 mg/1 indole-3-acetic acid. The ratio of green plants to albino was approximately 12.2.     

Macronutrient input from pollen in two regenerating pine stands in southeast Korea

This study examined macronutrient input from pollen in two naturally regenerating pine stands in southeast Korea. Durham gravity pollen collectors were used to measure pine pollen deposition and the macronutrients in the collected pine pollen were analyzed. In 1998, pine pollen deposition began just before 18 April and lasted for approximately 2weeks. Total pine pollen deposition differed between the two sampling sites; 27.5kgha^–1 was collected from the mature stand and 17.7kgha^–1 was collected from the young stand. The values for nutrient deposition from pine pollen are 549gha^–1 N, 78gha^–1 P, 240gha^–1 K, 45gha^–1 S and 22gha^–1 Mg at the mature stand and 353gha^–1 N, 51gha^–1 P, 151gha^–1 K, 27gha^–1 S and 14gha^–1 Mg at the young stand, suggesting that nutrients from pine pollen contribute to forest nutrient cycling. The pine pollen deposition values obtained from our study (17.7–27.5kg^–1ha^–1year^–1) are approximately 1/115–180-fold that of pine litterfall in Korea. If we take pollen nutrients into account, the contribution rate of pollen to the annual nutrient input is very high in our study (N 1/30, P 1/5, K 1/9 that of litterfall). Macronutrient deposition from pine pollen is concentrated temporally in spring. Although the annual contribution of nutrient mass by pollen is small compared to that of litterfall, the rapid turnover rate of pollen nutrients combined with episodic deposition suggests that pollen may play a disproportionate role in temperate pine forest nutrient cycling.     

Transgenic Plant Monitor (TPM): a relational database for the management and analysis of information in plant tissue culture and transformation laboratories

Increased public concern and strict statutory regulations relating tothe generation and exploitation of genetically modified organisms, make itimperative to track accurately individual plants through DNA transformationprogrammes. The ability to rapidly retrieve information associated withspecifictransgenic events and to provide accurate reports on demand is an increasinglyimportant feature for public research laboratories. Transgenic Plant Monitor(TPM) has been developed as a database structured to allow efficient recording,monitoring and analysis of the extensive and complex data generated in planttissue culture and transformation experiments. TPM is built upon the widelyavailable Microsoft Access database engine and can be readily adoptedand/or adapted by other users. The key features and the utility of TPM as aresearch tool are discussed in this article.     

In-vitro culture of tobacco pollen: gene expression and protein synthesis

Summary Immature pollen grains of Nicotiana tabacum L., cv Petit Havana were isolated at the mid-binucleate stage and cultured in vitro. During the first 66 h of in-vitro culture the pollen developed the same ability to set seed and germinate as pollen matured in vivo. No fertile pollen was produced when protein synthesis was inhibited temporarily at an early stage of development. In the case of inhibition at day 2 of development a delay in the total time necessary for maturation was observed that was equal to the length of time the inhibitor was applied. Hybridization experiments with a pollen-specific cDNA probe showed that the pattern of gene expression in vitro was similar to that in vivo. However, the model system differs from natural pollen development with respect to the dehydration period, which is absent in the model system, and the synthesis of proteins. Protein synthesis of in-vitro cultured pollen differed significantly from that of pollen developing in vivo, even though pollen maturation in vitro proceeded in the same time as in vivo, and led to fully matured fertile pollen. Pollen development in vitro is thus an ideal model system for studying gene expression in relation to fertility and for experimental manipulation of microsporogenesis.     

Effects of contact kairomone and experience on initial giving-up time

Reproduction and longevity of the anthocorid predators Orius laevigatus (Fieber) and Orius albidipennis (Reuter) (Heteroptera: Anthocoridae) were studied under controlled conditions in the laboratory. Three different diets were tested: eggs of the Mediterranean flour moth. Ephestia kuehniella Zeller, E. kuehniella eggs plus pollen, and pollen only. Small rooted plants of Spanish pepper (Capsicum annuum L. cv. Creta, long red) served as oviposition substrate and moisture source. In all treatments, total fecundity, oviposition period and female longevity of O. laevigatus were greater than that of O. albidipennis. When a diet of E. kuehniella eggs was supplemented with pollen, total fecundity of O. albidipennis was increased by about 40%. Female O. albidipennis fed only pollen laid five times less eggs than those fed flour moth eggs and pollen; also, longevity of females was shorter when only pollen was offered as food. Fecundity and longevity of O. laevigatus were not influenced when supplementing a diet of E. kuehniella eggs with pollen. Females of O. laevigatus receiving only pollen reduced egg production by about 60% but had a similar longevity as those receiving a diet including flour moth eggs. In either species, preoviposition period and egg hatch were not affected by diet. The ability of both anthocorids to use pollen as an alternative or additional food is discussed in relation to their practical use in integrated control programmes.     

Airborne pollen dispersal and survival on mount sutton (Canada)

Summary In order to find whether or not a pattern exist in both pollen concentration and viability along altitudinal transects, samples were collected volumetrically (VPPS) each 25 m, from 500 to 825 m, on Mount Sutton (45°04N; 72°32W) (970 m). Both minimum concentration and minimum viability were found at 725 m. Airborne pollen viability was species dependent, while airborne concentrations were not specific. Sampling height influence was also investigated volumetrically (BPS), by comparing paired samples at ground and 10 m levels. Again, pollen concentration pattern was found quite stable, while viability was found to be more height influenced, particularly at 725 m. The 725 m hinge altitude is located just above the June Mean Cloud Base altitude (657 m).