Plant regeneration from intergeneric somatic hybridization between Triticum aestivum L. and Leymus chinensis (Trin.) Tzvel

The suspension derived protoplasts of wheat (Triticum aestivum) cv. Jinan 177 were used as a recipient to fuse with the protoplasts of the ⁶⁰Co gamma-ray irradiated calli of Legmus chinensis. The wheat suspension cells and their protoplasts were not capable of differentiating to whole plants. The irradiated calli of L. chinensis were also the same. The protoplasts originated from the treated or untreated calli were both unable to divide under the conditions of this experiment. However, the fusion products grew and developed to whole plants which were identified as hybrids according to the analysis of chromosome, isozyme and morphology. The above result revealed that the lost regeneration capacity of both parents could be complementarily restored through somatic hybridization. This phenomenon also occurred with our work on Triticum aestivum (+) Haynaldia villosa, T. aestivum (+) Agropyron elongatum and T. aestivum (+) Psathyrostachys juncea.     

Seed abortion in the sexual counterpart of <Emphasis Type="Italic">Brachiaria brizantha</Emphasis> apomicts (Poaceae)

Gametophytic organization, fertilization and reproductive success are described for the fertile diploid Brachiaria brizantha accession BRA-002747 which is being raised for use in Brachiaria breeding programs, as well as to understand and control of apomixis in this genus. The current paper reports on reproductive biology and analysis of seed set in field experiments during three consecutive years. Unsuccessful seed production in this plant is believed to correlate with early inbreeding depression, based on the reproductive features analyzed. Caryopsis development was observed using differential interference contrast microscopy with seed set determined by the number of self- and open-pollinated pistils that fully developed into viable seeds. Developing and mature female and male gametophytes were observed in the context of flower phenology, morphology and anthesis patterns. Pollen viability was determined by acetocarmine staining and by observation of germination in vivo, which was also used to observe pollen tube/pistil interaction. Although normal development was observed in floral structures, anthesis and gametophytes, seed set was low, with 2 and 6% in self- and open-pollination, respectively, producing seed. Variations observed in the female organs, such as the presence of a hermaphrodite flower in 50% of the inferior floscules and the presence of multiple embryo sacs of the Polygonum type within the same ovule in 15% of the pistils, are not related to low fertility. The majority of pollen grains are viable, in spite of the reduced number of pollen tubes within the style and ovary carpel, and a developing caryopsis was observed in 70% of self-pollinated pistils, indicating successful double fertilization from 2 days after anthesis (DAA). Nevertheless, abortion gradually increased from 2 until 7 DAA and remains elevated until 12 DAA, when caryopsis maturity is achieved. These data confirm low seed set in this accession and indicate that low fertility is not a consequence of abnormalities, either in the floral or gamete structures, or pollen tube rejection, but most likely a consequence of inbreeding depression.     

Temperature-dependent development and oviposition models of Leptocorisa chinensis Dallas (Hemiptera: Alydidae)

Leptocorisa chinensis Dallas (Hemiptera: Alydidae) is known to cause pecky rice by sucking panicles of milk stage of rice. Based on its continuous spread and expanded damage area in Asian countries such as Japan with high reproduction potential, it is highly likely that L. chinensis will become an important rice pest in the near future. However, limited information is available to predict its distribution and occurrence. Thus, the objective of this study was to develop models for their development and oviposition. We investigated the development of L. chinensis immatures (from egg to adult) at 11 constant temperatures ranging from 16.2 to 35.3 °C and the oviposition of female adults at five constant temperatures ranging from 22.3 to 35.3 °C in this study. For L. chinensis immatures, the lower developmental threshold temperature, optimal developmental temperature, upper developmental threshold temperature were 12.7, 32.3, and 37.6 °C, respectively. The highest survival rate of immatures was observed at temperature of 25.2 °C and the highest mean total fecundity was 585.8 at 28.0 °C. This study provides basic information for the ecology of L. chinensis. It is applicable to forecast the phenology of its populations in the fields and to predict its future distribution under global warming.     

Self-pollination,style length development and seed set in self-compatible Asteraceae: evidence from Senecio vulgaris L.

Background: Variation in style length has been reported in Senecio vulgaris and has been associated with outcrossing rate.

Aims: To determine if (i) long styles lack germinated pollen on stigmas left to self-pollinate, (ii) successful self-pollination causes styles to stop elongating and shrink in length and (iii) seed set increases with the amount of pollen deposited on stigmas.

Methods: Determined germinated self-pollen on stigmas of long and short styles after auto-self-pollination; scored style length over 48 h in self-pollinated and non-pollinated florets; recorded seed set after placing different amounts of pollen on stigmas.

Results: Most long-styled florets had zero or low amounts of germinated pollen on stigmas in contrast to most short-styled florets. Styles initially elongated to the same length in self-pollinated and non-pollinated florets, then shrank in length in self-pollinated florets while continuing to elongate in non-pollinated florets. Seed set increased with number of pollen grains deposited on stigmas.

Conclusions: Successful self-pollen deposition and/or germination on stigmas of S. vulgaris are indicated by presence of short styles, whereas the opposite is indicated by presence of long styles in florets left to self-pollinate. Self-pollination causes styles to shrink after initially elongating. Seed set is dependent on the amount of pollen deposited on stigmas.     

Critical phases in the seed development of common juniper (Juniperus communis)

Common juniper (Juniperus communis L.) populations in northwest European lowlands are currently declining in size and number. An important cause of this decline is a lack of natural regeneration. Low seed viability seems to be one of the main bottlenecks in this process. Previous research revealed a negative relation between seed viability and both temperature and nitrogen deposition. Additionally, the seeds of common juniper have a variable ripening time, which possibly influences seed viability. However, the underlying mechanisms remain unresolved. In order to elucidate this puzzle, it is important to understand in which phases of seed production the main defects are situated, together with the influence of ripening time. In this study, we compared seed viability of populations with and without successful recruitment. We examined three seed phases: (i) gamete development; (ii) fertilisation and early‐embryo development; and (iii) late‐embryo development. After the first two phases, we found no difference in the percentage viable seeds between populations with or without recruitment. After late‐embryo development, populations without recruitment showed a significantly lower percentage of viable seeds. These results suggest that late‐embryo development is a bottleneck in seed development. However, the complex interaction between seed viability and ripening time suggest that the causes should be in the second seed phase, as the accelerated development of male and female gametophytes may disturb the male–female synchrony for successful mating.     

Reproductive potential and seed fate of Sclerocarya birrea subsp. caffra (marula) in the low altitude savannas of South Africa

Even though Sclerocarya birrea subsp. caffra (marula) is a well-studied, keystone tree species with high ecological, commercial and cultural value, significant gaps in our understanding of its reproductive biology exist, particularly the factors limiting fruit and seed production, seed fate and the persistence of the seed bank. Therefore, a detailed quantitative assessment of these factors was conducted at five sites in the low altitude savannas of South Africa. Sites varied with respect to fire regime, large mammals, geology and rainfall. Most sites showed male-biased secondary sex ratios and the minimum fruiting stem diameter ranged between 7.1 and 15.7 cm across sites. Sites with higher levels of disturbance (fire and large browsers) had trees producing fruit at larger minimum stem diameters than sites with lower levels of disturbance. Fruit production was highly variable between individuals, within and between sites, and from year to year. Variability in fruit production across years at one site was greater than the variability across sites in one year, indicating that drivers such as weather, insect herbivory, fire and predator numbers, which vary annually, play a greater role than more constant drivers such as mammalian herbivory, soil types or long-term rainfall. No significant relationship was found between environmental variables (rainfall and temperature) and annual fruit production, indicating a trade-off between vegetative growth and reproduction between years. Since marula fruits are large and heavy, the species relies primarily on mammalian dispersal agents such as the African elephant, which have also been shown to increase the germination rate. However, rodents also appear to play a significant role in seed dispersal. Seed predation rates tend to be highest in areas of low disturbance (no fire and no large browsers). While marula has a small persistent seed bank, recruitment appears to be reliant on the current season's fruit crop. This study provides a detailed quantitative assessment of important reproductive and seed fate vital rates for future population modelling.     

Ovule morphology, embryogenesis and seed development in three Hylocereus species (Cactaceae)

Pre-embryonic and embryonic stages and seed developments were studied in the diploids Hylocereus monacanthus and Hylocereus undatus and the tetraploid Hylocereus megalanthus. Ovule morphology was similar among species except for micropyle entrance. H. monacanthus had the thickest and most robust suspensor. Embryo developmental time, measured from fertilization to maturity, was significantly more prolonged in H. megalanthus. Typical to Cactaceae, the seed coat was formed by one layer of sclerenchymatous cells, but was more lignified in H. megalanthus. Morphological features common to all species included (1) cellular type endosperm with independent patterns of development in the chalazal and micropylar zones, forming a haustorium layer from the chalazal zone to the embryo; (2) an endothelial layer surrounding the embryo sac almost complete; (3) a nucellar summit growing into the micropyle; and (4) a placental obturator and a funicle connecting the ovarian tissue to the ovule. Seed development was typically endospermic (exendospermic orthodox seeds). Anomalies included two egg cells in the same embryo sac, two embryos developing in the same ovule, and embryos developing from the chalazal pole region. Total seed number and seed viability were significantly lower in H. megalanthus than in the other two taxa. Embryos at different developmental stages were observed in aborted H. megalanthus seeds.     

Effect of ovular receptivity on seed set and fruit development in cucumber (Cucumis sativus L.)

Summary Seed set and fruit development in cucumber (Cucumis sativus L.) were studied in relation to female flower receptivity from day — 2 before anthesis to day + 2 after anthesis. The female cucumber flower is protogynous. The pistil was receptive 2 days before anthesis. The iso-electric focusing (IEF) patterns of the stigma/style proteins, were identical from day -5 to day +2. In pollinated flowers in vivo germination and pollen-tube growth in the ovary were affected by pistil age from day -2 to day +2. In addition, differences in sectorial filling in full seeds were observed within the fruits. A negative correlation was observed between the frequency of fertilized ovules in the pedoncular part of the fruit and ovary length at the time of pollination. In the whole fruit, significant differences in the number of full seeds and fruit size at maturity were found, and these were observed to be correlated with the various stages of female flower maturation at pollination. The day -2 and day +2 stages yielded the smallest fruits with few full seeds compared to the day -1, day 0 and day +1 stages, which had the biggest fruits and a large number of full seeds. A strong positive correlation was found between total seed number (including full and empty seeds), fruit length and weight at maturity. All these results suggest that both seed set in the different parts of the fruit and fruit development are controlled by ovular receptivity rather than by stigma/style receptivity.     

Effect of tamarind (Tamarindus indica) seed husk tannins on in vitro rumen fermentation

This study was conducted to determine the effect of tamarind seed husk (TSH) as a source of tannin on various parameters of rumen fermentation in vitro. The TSH contained 14% tannin (DM basis). The biological interference of TSH tannin on rumen fermentation was assessed using polyethylene glycol (PEG) 6000 as an indicator. Three compound feed mixtures (CFM) were prepared either without TSH (CFM-I), with 2.5% TSH (CFM-II) and with 7.5% TSH (CFM-III). Parameters studied were in vitro gas production with PEG, rate of substrate degradation, and microbial protein synthesis. Addition of PEG to TSH resulted in an increase in gas production from 5.5 to 16.5 ml per 200 mg DM. Presence of TSH tannin depressed cumulative gas production by 16.8% in CFM-II, and by 29.2% in CFM-III during initial stages of fermentation (i.e. at 8 h). Rate of substrate disappearance (T^1/2) was 14.4, 17.6 and 20.5 h in CFM-I, CFM-II and CFM-III, respectively. Irrespective of the carbohydrate source, presence of TSH tannin improved the efficiency of microbial protein synthesis in vitro. Thus, TSH is a natural source of tannin that can be used to beneficially manipulate rumen fermentation.     

Effects of self-, chase and mixed self/cross-pollinations on pistil longevity and fruit set in Ceiba species (Bombacaceae) with late-acting self-incompatibility

BACKGROUND AND AIMS: Late-acting self-incompatibility (LSI), in which selfed flowers fail to form fruits despite apparently successful growth of the pollen tubes to the ovules, is a contentious and still poorly understood phenomenon. Some studies have indicated pollen tube-pistil interactions, and major gene control. Others favour an early acting inbreeding depression explanation. METHODS: Experimental pollinations, including selfs (in a subsample of which the style was cut before pollen tubes reached the ovary), chase self/cross-pollinations, crosses, and mixed self/cross-pollinations were used to study floral/pistil longevity and effect on fruit set and seed yield in two Ceiba species known to have LSI. RESULTS: Self-pollinations, including those with a cut style, had extended floral longevity compared with unpollinated flowers. Chase pollinations in which cross-pollen was applied up to 3 h after selfing set fruits, but with reduced seed set compared with crosses. Those with cross-pollen applied at 4 and 8 h after self-pollination all failed to set fruits. Flowers subjected to 1 : 1 and 2 : 1 self/cross-pollinations all produced fruits but again with a significantly lower seed set compared with crosses. CONCLUSIONS: Extended floral longevity initiated with self-pollen tubes growing in the style indicates some kind of pollen tube-pistil interaction. Fruit set only in chase pollinations up to 3 h implies that self-pollen tubes either grow more slowly in the style or penetrate ovules more slowly on arrival at the ovary compared with cross-tubes. This agrees with previous observations indicating that the incidence of penetrated ovules is initially lower in selfed compared with crossed pistils. However, the low seed yield from mixed pollinations indicates that self- and cross-pollen tubes arrive at the ovary and penetrate ovules more or less simultaneously. Possible explanations for these discordant results are discussed.     

Dynamics of maternal and paternal effects on embryo and seed development in wild radish (Raphanus sativus)

Background and Aims

Variability in embryo development can influence the rate of seed maturation and seed size, which may have an impact on offspring fitness. While it is expected that embryo development will be under maternal control, more controversial hypotheses suggest that the pollen donor and the embryo itself may influence development. These latter possibilities are, however, poorly studied. Characteristics of 10-d-old embryos and seeds of wild radish (Raphanus sativus) were examined to address: (a) the effects of maternal plant and pollen donor on development; (b) the effects of earlier reproductive events (pollen tube growth and fertilization) on embryos and seeds, and the influence of embryo size on mature seed mass; (c) the effect of water stress on embryos and seeds; (d) the effect of stress on correlations of embryo and seed characteristics with earlier and later reproductive events and stages; and (e) changes in maternal and paternal effects on embryo and seed characteristics during development.

Methods

Eight maternal plants (two each from four families) and four pollen donors were crossed and developing gynoecia were collected at 10 d post-pollination. Half of the maternal plants experienced water stress. Characteristics of embryos and seeds were summarized and also compared with earlier and later developmental stages.

Key Results

In addition to the expected effects of the maternal plants, all embryo characters differed among pollen donors. Paternal effects varied over time, suggesting that there are windows of opportunity for pollen donors to influence embryo development. Water-stress treatment altered embryo characteristics; embryos were smaller and less developed. In addition, correlations of embryo characteristics with earlier and later stages changed dramatically with water stress.

Conclusions

The expected maternal effects on embryo development were observed, but there was also evidence for an early paternal role. The relative effects of these controls may change over time. Thus, there may be times in development when selection on the maternal, paternal or embryo contributions to development are more and less likely.     

Proteins in development and germination of a desiccation sensitive (recalcitrant) seed species

In the recalcitrant seeds of Avicennia marina, protein content and the rates of protein synthesis increase during histodifferentiation. This is similar to the situation in desiccation tolerant seeds. During the stage of reserve accumulation the protein content and rates of synthesis remain constant and there is no de novo synthesis of proteins which might qualify as storage proteins. There is also no change in the nature of proteins present in either axis or cotyledonary tissues during development or germination. Similarly, fluorographs of axis proteins show only very limited changes in the patterns of protein synthesis during development and germination, at least until the onset of root growth. Heat-stable proteins are present from an early developmental stage. However, no late embryogenic abundant (LEA) proteins are synthesised during the late stages of development, indicating that seedling establishment is independent of such maturation proteins. It is suggested that the lack of desiccation tolerance of A. marina seeds might be related to the absence of desiccation-related LEAs. Although the rate of protein synthesis increases during germination, protein metabolism appears to remain qualitatively the same as that occurring during development. The present results suggest that in these desiccation sensitive seeds, protein metabolism characterising development changes imperceptibly into that of germination.     

Pollen and resource limitations to lifetime seed production in a wild population of the endangered plant Disanthus cercidifolius var. longipes H. T. Chang (Hamamelidaceae)

Disanthus cercidifolius Maxim. var. longipes H. T. Chang, a plant species that only occurs in a few counties in Hunan, Jiangxi and Zhejiang Provinces and with a relatively small number of individuals, is ranked as a second Class endangered species for conservation in China. We have studied the effect of pollen and resources available to female reproduction, and the reproductive mechanism of “excess flowers with low fruit set” in Disanthus cercidifolius Maxim. var. longipes H. T. Chang was discussed. Results are as follows Pollen from different sources has significant effects on fruit set and seed set of Disanthus cercidifolius Maxim. var. longipes H. T. Chang. The pollen source rather than pollen numbers significantly affected reproduction of this species. In wild populations, producing one fruit needs about 54.8 flowers, and one satiation seed needs about 6.60 flowers or 83.19 ovules. After fertilizing, which was propitious to flower development, the abortion rate of flower buds was decreasing, but the flowering rate was increasing. The fruit set and seed set was also significantly increasing, while abortion rate of fruit was significantly decreasing. With the increasing percentages of cutting leaves, the fruit set decreased, but the abortion rate of fruit shows no significant differentiation among treatments. After cutting branches that were puny, broken and insectin-fested branches, the flower number seemed to be decreasing, but the fruit set and seed set all increased significantly. After removing some flowers, the fruit set was calculated with respect to the number of flowers remaining after the treatment increased with increasing of percentages of flower removal, whereas fruit set calculated with respect to the initial number of flowers remained constant, and the mean weights of per fruit and per seed all decreased significantly. Sufficient spatial or temporal heterogeneities in nutrient levels might allow limitation of seed set by resources and pollen in a natural population, while supplying resources may indirectly affect pollination by increasing attraction of the flowers to pollinators. There were very low fruit and seed sets in natural populations of Disanthus cercidifolius Maxim. var. longipes H. T. Chang. Different factors may have interacted to effect a low fruit set. A joint adoption of the “selection abortion hypothesis”, “ovary reserve hypothesis” and “male function hypothesis” seems to be the most likely explanation for the reproductive strategy of “excess flowers with few fruit sets” in Disanthus cercidifolius Maxim. var. longipes H. T. Chang. __________ Translated from Acta Ecologica Sinica, 2006, 26(2): 496–502 [译自: 生态学报]     

Comparative morphology and physiology of fruit and seed development in the two shrubs Rhus aromatica and R. glabra (Anacardiaceae)

Morphology and physiology of fruit and seed development were compared in Rhus aromatica and R. glabra (Anacardiaceae), both of which produce drupes with water-impermeable endocarps. Phenology of flowering/fruiting of the two species at the study site was separated by ∼2 mo. However, they were similar in the timetable and pattern of fruit and seed development; it took ∼2 mo and ∼1.5 mo for flowers of Rhus aromatica and R. glabra, respectively, to develop into mature drupes. The single sigmoidal growth curve for increase in fruit size and in dry mass of these two species differs from the double-sigmoidal one described for typical commercial drupes such as peach and plum. Order of attainment of maximum size was fruit and endocarp (same time), seed coat, and embryo. By the time fruits turned red, the embryo had reached full size and become germinable; moisture content of seed plus endocarp had decreased to ∼40%. The endocarp was the last fruit component to reach physiological maturity, which coincided with development of its impermeability and a seed plus endocarp moisture content of <10%. At this time, ∼50, 37, and 13% of the dry mass of the drupe was allocated to the exocarp plus mesocarp unit, endocarp, and seed, respectively. The time course of fruit and seed development in these two species is much faster than that reported for other Anacardiaceae, including Rhus lancea, Protorhus, and Pistacia.     

On the development of the deciduous teeth in the common seal (Phoca vitulina)

Information on the development of teeth in seals is rare. In this study, histological details are presented from fetuses and several postnatal stages of the common seal (Phoca vitulina), showing that the deciduous teeth undergo a very rapid, short-term, and somewhat incomplete development. This means that the permanent dentition can and also has to ‚out-pace’ the deciduous dentition, because Phoca vitulina, contrary to fur seals, has a very short suckling period after which there is an abrupt change to normal feeding (crabs, fishes).