Plant Reproductive Biology Research Articles

ADAPTIVE SIGNIFICANCE OF HERKOGAMY AND FLORAL BEHAVIOUR

With their critical role in plant pollination and mating system, the adaptive significance of herkogamy and floral behavior has well been studied in plant reproductive biology and evolutionary ecology. Here we review recent progress in this field, especially discuss the adaptive significance of movement approach herkogamy in monadelphous tube in Malvaceae, which involves decrease of herkogamy resulting from the curvature of stigma lobe. Herkogamy, the spatial separation of pollen presentation and pollen receipt within flowers, appears in many animal_pollinated plants. Due to its positive correlation with outcrossing rates in some species with mixed_mating systems, herkogamy has been previously considered as a mechanism to prevent self_pollination. However, increasing evidences suggest that herkogamy may act as a mechanism to reduce interference between the reproductive functions of female and male organs. Functional studies of heterostylous species indicate that sex_organ reciprocity serves to promote cross_pollen transfer between floral morphs and that enantiostyly and stigma_height dimorphism function in a similar manner. Intra_floral sex interference often contains physical interference and pollen clogging. The former involves stamens obstructing the deposition of outcrossing pollen on stigmas and pistil reducing pollen export (an experimental evidence is given recently). The latter involves pollen discounting and ovule discounting, and its experimental evidence has been largely reported in many plants. The behaviors of different floral parts (style, stamen, pollen, corolla, etc.) may have adaptive significance, including reducing intrafloral male_female interference, avoiding self_pollination, promoting delayed autonomous selfing, and responding to the harsh environment. Movement approach of herkogamy in monadelphous tube in Malvaceae, making the herkogamy decrease by the curvature of stigma lobe, is unusual and intriguing, and its adaptive significance may involves promoting outcrossing, facilitating delayed selfing if outcrossing fails, and interferences between two sexual organs. We believe that the trends studying on the their functions are transiting from the research stage mainly depending on the description to comprehensive research phase combining modern experimental technology (e.g. the molecular markers of SSR, SNP, AFLP) and advanced apparatus multi_seasons with traditional method, and with the development of the capacity of field experiments and control conditions,transiting from traditional and classical observations to combining floral manipulation in the field experiments.

Seed-spitting Primates and the Conservation and Dispersion of Large-seeded Trees

Primate frugivory may reduce density-dependent predation on seeds and seedlings via effective seed dispersal. Accordingly, the tendency of cercopithecines to spit and scatter seeds > 4 mm wide could represent a prominent means of dispersal. However, the importance of seed-spitting may vary according to the life history adaptations of plants. Indeed, the actions of cercopithecines may be incongruent with the reproductive biology of plants that rely on large frugivores to swallow and defecate their seeds. This possibility raises conservation concerns because large frugivores are often susceptible to extirpation or extinction from hunting and habitat fragmentation. It is therefore important to determine if cercopithecines have a compensatory effect; that is, whether or not seed-spitting effectively conveys large seeds to recruitment sites. To test this concept, we used geospatial techniques to measure and analyze the dispersion of tree species dispersed by elephants, chimpanzees, and cercopithecines to different spatial extents. We studied adult trees of Balanites wilsoniana, Chrysophyllum gorungosanum, and Uvariopsis congensis in a 2.2-ha plot in Kibale National Park, Uganda. Despite the tendency of cercopithecines to spit the seeds of Uvariopsis congensis, adult trees were highly clumped, with a modal nearest-neighbor distance of < 5 m and a crown overlap of 1.5 m. Virtually identical results for Balanites wilsoniana and Chrysophyllum gorungosanum, the seeds of which are not spat, suggest that seed-spitting may be a poor mechanism of dispersal for some large-seeded plants.

Plant reproductive genomics at the Plant and Animal Genome Conference

Exciting advances in our understanding of plantreproductive biology are being spurred both bynew research on established model systems andby the emergence of new models. Moreover, com-parative analyses are placing knowledge derivedfrom each of these systems into an evolution-ary framework and thus providing insights intothe processes responsible for the diversity offorms we see today. The number of species withlarge EST sets for floral transcriptomes is grow-ing rapidly (Figure 1;

Are ?mating systems? ?breeding systems? of inconsistent and confusing terminology in plant reproductive biology? or is it the other way around?

Are ?mating systems? ?breeding systems? of inconsistent and confusing terminology in plant reproductive biology? or is it the other way around?

The global decline of pollination services

Pollination, the transfer of pollen from anthers to stigmas achieved mainly by animals, is vital to plant reproductive biology in almost all terrestrial ecosystems. This process is critical for the conservation and sustainability of the world's flora and fauna. The decline of pollination services caused by chemicals, pests, extreme weather, habitat destruction and/or fragmentation, reduces the reproductive output of plants. In extreme cases this could cause extinction of plants and animals and ultimately lead to changes in the landscape and in ecosystem function. Conservation concerns for pollination have started to take on a greater profile over the past decade. However, there is still a need for policies that are sensitive to the importance of pollinators. More intensive efforts are required to widen the general understanding of the essential value of plant-pollinator interactions for agricultural and natural resource conservation.

Short-term Costs of Sexual Reproduction in the Clonal Moss Hylocomium splendens

Abstract Bryophytes may be more appropriate than vascular plants for testing hypotheses relating to plant reproductive biology due to their relatively simple structure. Nevertheless, they have rarely been used for this purpose, and remain poorly known with respect to reproductive biology. It is, for instance, still not known if bryophytes generally exhibit reproductive costs. We addressed the cost of producing reproductive structures in a bryophyte species, the clonal moss Hylocomium splendens, by following a SE Norwegian boreal spruce forest population in which sporophytic female mature segments grew intermingled with segments devoid of sporophytes for five years. By comparing segment sub-populations with and without sporophytes, respectively, we demonstrated that production of sporophytes had significant costs in terms of less favorable size development of daughter segments, lower branching frequency, and higher risk of not producing new annual segments. From the observed patterns of size development an...

Two new methods of rapid detoxification in opioid dependence: what does general anaesthesia really add to the effect?

The Organization for Tropical Studies (OTS) has played a pivotal role in our understanding of tropical ecosystems' structure and function. For more than fifty years, OTS has contributed to the training of three generations of tropical biologists and facilitated, supported, and promoted leading-edge research in its field stations. Plant reproductive ecology and genetics have been a significant focus of OTS research since the early 1960s, and Dr. K.S. Bawa made a significant contribution to the advancement of this field. His work improved our understanding of the diversity and evolution of breeding systems in tropical forests, their phenology and pollination ecology, and their mating and genetic structure. We argue that his work inspired other tropical biologists' work and used the work of one of the authors for illustration when appropriate. We point out the need for research in critically important topics to slow down biodiversity loss, prevent the collapse of tropical systems in a changing climate, and the emergence of zoonotic disease. We suggest future research topics for the OTS field stations, including in plant reproductive biology.

Samara Dispersal in Boxelder: An Exercise in Hypothesis Testing

Pedagogical surveys have shown that traditional approaches to teaching botany, with their emphasis on preserved specimens, prepared slides and slow-to-develop physiological experiments, tend to lead students to one conclusion-plants are boring (Uno 1994). Surveys have also shown that students have a strong preference for hands-on experiments which utilize living material and generate fast results. The incorporation of such experiments into botany or ecology exercises is especially difficult in the dead of winter in northern climes. We present here a fun, inexpensive and pedagogically useful laboratory exercise which involves indoor studies of the dispersal properties of the winged fruits (samaras) of boxelder (Acer negundo L.) trees. The exercise engages students in the processes of hypothesis testing, experimental design, and data analysis, as well as introducing them to some important concepts relating to functional ecology, succession and plant reproductive biology. An attractive feature of the exercise presented is its flexibility. If scheduling and the abilities of the students permit, the exercise can easily be re-tailored to incorporate more independent inquiry on the part of the students; alternatively, it could be pared down to be a highly-regimented cookbook-type lab. We have adapted sort of a middle ground between these two approaches, so that the exercise does require independent inquiry by the students, but can also be completed in a single, three-hour lab period. In our particular case, a third of this time is devoted

Green fluorescent protein (GFP) as a marker during pollen development.

The transient expression of three mutant forms of green fluorescent protein (GFP) genes, GFP4, GFP5ER, and GFP4S65C, under several constitutive and pollen-specific promoters throughout pollen development in Nicotiana tabacum, Arabidopsis thaliana and Antirrhinum majus is described. Immature pollen of tobacco, Arabidopsis and snapdragon, isolated at different developmental stages, were bombarded with plasmids containing the GFP and cultured in vitro for several days until maturity. The expression of GFP was monitored every day during in vitro maturation, germination and pollination, as well as after in situ pollination. The expression pattern of each GFP construct was compared in parallel experiments to that of beta-glucuronidase (GUS) constructs expressed by the same promoters. The results show that the expression level of all three GFP mutant forms was dependent on the strength of the promoter used. The strongest promoter was the DC3 promoter, and no notable differences in the intensity and brightness of all three versions of GFP were observed. GFP-expressing pollen from tobacco and snapdragon developed in vitro for several days until maturity and germinated in vitro as well as on the surface of stigmata, strongly suggesting that all three GFPs are not toxic for the development of functional pollen. Furthermore, stably transformed tobacco plants expressing GFP under the control of the strong pollen-expressed DC3 and LAT52 promoters were not impaired in reproductive function, confirming that GFP can be used as a non-destructive marker for plant reproductive biology and development.

Reproductive biology of island and mainland populations of Primula mistassinica (Primulaceae) on Lake Huron shorelines

To investigate the influence of insularity on plant reproductive biology at a local geographic scale, we examined aspects of reproduction in distylous Primula mistassinica Michx. (Primulaceae) on Lake Huron shorelines of the Bruce Peninsula and adjacent Tobermory Islands in Ontario, Canada. A total of 7 mainland and 13 nearshore island populations were compared. Controlled pollinations demonstrated that P. mistassinica possesses a dimorphic incompatibility system with intermorph crosses setting significantly more seeds than self or intramorph crosses. Floral morphology, population style-morph ratios, and seed fertility were compared in mainland and nearshore island populations to determine whether there was evidence for differences in reproductive traits between these areas. Style-morph ratios did not differ significantly from equilibrium expectations, and there were no consistent differences between island and mainland populations in floral morphology or fertility. Rather, the generalized pollination system of P. mistassinica and extensive historical opportunities for colonization appear to have mitigated insular effects so that proximate ecological factors are more relevant to the current reproductive biology of populations.Key words: distyly, insularity, pollination, reproductive biology.

The titan mutants of Arabidopsis are disrupted in mitosis and cell cycle control during seed development.

We describe in this report a novel class of mutants that should facilitate the identification of genes required for progression through the mitotic cell cycle during seed development in angiosperms. Three non-allelic titan (ttn) mutants with related but distinct phenotypes are characterized. The common feature among these mutants is that endosperm nuclei become greatly enlarged and highly polyploid. The mutant embryo is composed of a few giant cells in ttn1, several small cells in ttn2, and produces a normal plant in ttn3. Condensed chromosomes arrested at prophase of mitosis are found in the free nuclear endosperm of ttn1 and ttn2 seeds. Large mitotic figures with excessive numbers of chromosomes are visible in ttn3 endosperm. The ttn1 mutation appears to disrupt cytoskeletal organization because endosperm nuclei fail to migrate to the chalazal end of the seed. How double fertilization leads to the establishment of distinct patterns of mitosis and cytokinesis in the embryo and endosperm is a central question in plant reproductive biology. Molecular isolation of TITAN genes should help to answer this question, as well as related issues concerning cell cycle regulation, chromosome movement and endosperm identity in angiosperms.

The role of theory in an emerging new plant reproductive biology

Recent empirical studies hint at an end to the historical solitude between pollination and mating system approaches to plant reproductive character evolution. Now is an opportune time to distill theoretical results into comprehensible insight, and to integrate these findings into the emerging new plant reproductive biology. We outline four theoretical insights for understanding the evolution of reproductive characters, and show how these allow researchers to dissect complex ecological scenarios into clear and evolutionarily relevant components.

Anatomically preserved vojnovskyalean seed plants in Upper Pennsylvanian (Stephanian) marine shales of North America

Upper Pennsylvanian dysoxic marine shales of midcontinent North America yield permineralized remains of apparently extrabasinal vegetation. A large percentage of the plants are surprisingly unlike the well known swamp, fluvial and lacustrian floras of the late Paleozoic paleotropics, revealing numerous aspects of the morphology, anatomy and reproductive biology of plants that may have been ancestral to the dominant taxa of the Mesozoic. Included among the assemblages are ovulate coniferophyte remains that demonstrate the occurrence of vojnovskyalean seed plants in equatorial Euramerica. Specimens consist of simple ovulate cones that are more-or-less clustered along eustelic stems in the axils of helically arranged, strap-shaped leaf bases, and are described as Sergeia neuburgii new genus and species. Individual cones are up to approximately 2 cm long and 1.5 cm in maximum diameter, with helically arranged scales and sporophylls that diverge from a eustelic axis. Scales occur in the basal region of the cone, and are laminar and pointed. Sporophylls are borne distally. One specimen shows about 45 sporophylls, each of which terminates as one erect ovule. Most of the other cones have abraded apices, and terminate in relatively terete foliar appendages that are interpreted to be sporophyll bases. Ovules are flattened and winged, approaching 180° rotational symmetry. Integument histology, vascular tissue distribution and pollen chamber structure are similar to those of cordaiteans and callistophytalean seed ferns. Sergeia adds to the number of late Paleozoic conifer-like plants that do not conform to the Pinopsida as traditionally circumscribed, and poses additional questions to assumptions of monophyly for coniferophytes and for conifers sensu lato.

Physiological activity in persistent bulbils of Agave vilmoriniana (Agavaceae)

Plants of Agave vilmoriniana are unique members of a reproductively diverse genus since they produce prolific numbers of both bulbils and viable seeds. Bulbils were observed to remain attached to the flowering stalk into a second summer, instead of abscising in the year they developed. Hence, a number of hypotheses were tested to establish the physiological basis for their longevity and evaluate their influence upon the plant's reproductive biology. Bulbils produced following anthesis were abundant (&gt;2000 bulbils), large (0.44 g dry mass per individual), and their combined leaf surface area (one side) could exceed 3 m2. Thus, the current‐year inflorescence may act as a photosynthate source. Second‐year, attached bulbils are healthy‐looking, even after leaves of the parent plant have senesced, since maternal roots continue to absorb rain water. Rehydrated 2nd‐yr bulbils resume Crassulacean acid metabolism, sometimes demonstrating net daytime tissue acidification. Water conservation by bulbils is very efficient, exhibiting very low cuticular conductances (0.016‐0.0035 mm/s). Bulbils detach over all climatic seasons after having formed &gt;3 and &gt;18 root primordia in their 1st and 2nd year, respectively. About one‐third of bulbils are capable of forming roots after a 1‐yr storage at 35°C, when their water contents averaged 37%. Irrigated bulbils produce water‐absorbing roots within 2 d, with de novo chlorophyll synthesis and nocturnal acidification commencing within 4 d. Two bulbils were observed to root and become established in shaded microhabitats during this 2‐yr study of 29 plants.

Emerging data on pollen tube growth and fertilization in flowering plants, 1990?1995

Since its discovery at the end of the last century, double fertilization remains of central interest in plant reproductive biology research. Although the sequence of events leading to fertilization is well known from cytological studies, the underlying mechanisms remain to be elucidated. This now seems feasible by the diversification and refinement of recently developed technologies presented in this review. The progress made during the last five years in understanding pollen tube guidance, discharge into the embryo sac, and gametic fusion are described. Future directions are also discussed.

Modeling of Discontinuous Relationships in Biology with Censored Regression

Discontinuous relationships between variables are common in biological data. Discontinuities can sometimes give the appearance of curvilinearity, which suggests the data should be analyzed with nonlinear models. Here we show that often a more meaningful analysis can be obtained with censored regression techniques. In a censoring model all points below (or above) a certain threshold are observed only by the value of the threshold (e.g., a baseline temperature). We illustrate the method with an example from plant reproductive biology: plant reproductive mass is never negative but becomes positive only after some "capacity" to flower reaches a threshold. The vegetative mass at which the threshold is reached and the relationship between reproductive mass and vegetative mass above the threshold are estimated from data. Using censored regression with real and simulated data shows that apparent curvilinearity suggested by models that do not account for censoring can be an artifact.

Plant reproductive biology of herbaceous monocots in a Venezuelan tropical cloud forest

The reproductive biology of 29 herbaceous understory monocot species was studied in a tropical cloud forest of northern coastal Venezuela (Henri Pittier National Park). Of the 23 plant species, 6 (26.1%) were self-incompatible and 17 (73.9%) self-compatible, the latter consisting of 12 (52.2%) fully self-compatible and 5 (21.7%) partially self-compatible species. An analysis of sexual systems and temporal variation of sex expression showed that of 29 monocot species, 14 (48.3%) were hermaphrodite and adichogamous, 14 (48.3%) monoecious and dichogamous, and one (3.4%) dioecious. The combination of monoecy and dichogamy prevented autogamy in 11 (91.7%) of the 12 self-compatible and monoecious species; one (8.3%) was autogamous. Of all species, 24 (82.8%) were obligate outbreeders, 2 (6.9%) spontaneously autogamous, and 3 (10.3%) partially autogamous. Ovule and flower abortion were not significantly different between the different groups. Pollen-ovule ratio was significantly different between monoecious and hermaphrodite species. The number of pollen grains and ovules per flower and the pollen-ovule ratio were variable among various pollination types. The average pollen-ovule ratio was higher in beetle-, dipteran-, and wind-pollinated species than in bee-, bird-, and bat-pollinated species. The first three pollination types were restricted to monoecious species, and the second three groups were restricted to hermaphrodite species. Of 33 plant species investigated, 12 (36.4%) displayed vegetative reproduction. The reproductive features of the understory monocot species are discussed in the context of life form, devices of cross-pollination, and geological history of the tropical cloud forest.

EXPERIMENTAL PLANT REPRODUCTIVE BIOLOGY AND REPRODUCTIVE CELL MANIPULATION IN HIGHER PLANTS: NOW AND THE FUTURE

Experimental plant reproductive biology has recently emerged as a new form of experimental embryology characterized by the direct experimental isolation and manipulation of reproductive cells and protoplasts. This work is fostered by current multidisciplinary trends in the sciences and serves to deepen our knowledge about the control of reproductive processes by providing novel in vitro material. The techniques of experimental plant reproductive biology also show great potential in providing new means for biotechnology, leading to significant refinements in plant breeding in higher plants that may eventually permit direct reproductive cell engineering. Recent achievements by our research group in experimental manipulation and biological studies of pollen protoplasts, generative cells, sperm cells, and embryo sacs are reviewed, and some ideas about future developments in this new area are presented.

Experimental Plant Reproductive Biology and Reproductive Cell Manipulation in Higher Plants: Now and the Future

Experimental plant reproductive biology has recently emerged as a new form of experimental embryology characterized by the direct experimental isolation and manipulation of reproductive cells and protoplasts. This work is fostered by current multidisciplinary trends in the sciences and serves to deepen our knowledge about the control of reproductive processes by providing novel in vitro material. The techniques of experimental plant reproductive biology also show great potential in providing new means for biotechnology, leading to significant refinements in plant breeding in higher plants that may eventually permit direct reproductive cell engineering. Recent achievements by our research group in experimental manipulation and biological studies of pollen protoplasts, generative cells, sperm cells, and embryo sacs are reviewed, and some ideas about future developments in this new area are presented.

Dissecting Factors Responsible For Individual Variation in Plant Fecundity

This paper analyses, on an individual plant basis, the various components determining seed production in the evergreen shrub Lavandula latifolia (Labiatae), in order to estimate their relative contributions to individual differences in fecundity. The relationships between fecundity and age, size, and growth rate are also examined. Experimental pollination and watering were done in an attempt to alter natural patterns of partial fecundity components. Fecundity of individual plants is partitioned into its absolute (number of inflorescences, number of flowers per inflorescence) and relative (fruits/flower and seeds/fruit) partial components, and the following questions are addressed: (1) Are the individual differences in relative components of fecundity? (2) What are the proportional contributions of relative and absolute components of fecundity to individual variation in seed production? (3) Are relative measures of reproductive success reliable predictors of individual differences in fecundity? (4) When induced experimentally, do changes in partial fecundity components translate into modifications of the population's ranking of absolute fecundities? Fecundity depended more on plant size than age, was unrelated to growth rate, and was limited by water, but not pollen, availability. Individual plants differed in all components of fecundity examined, and differences were consistent among years. The proportional contributions of the various components to individual differences in fecundity were very unequal. Almost all variation among plants in seed production (°90% of variance) was explained by the variances and covariances of number of inflorescences and number of flowers per inflorescence. Variation among plants in the two relative components (fruit and seed set), even though statistically significant, had a negligible influence on individual differences in fecundity. These patterns remained invariant despite significant modification of flower production and fruit set induced by artificially watering a part of the study population. Fruit and seed set alone are unreliable indicators of individual differences in the maternal component of fitness in L. latifolia, and a review of relevant literature indicates that this probably applies to other polycarpic plants as well. Plant reproductive biology studies may make erroneous inferences if they consider exclusively data on relative fruit and seed set, and neglect the absolute components of individual differences in fecundity. It is proposed that, to circumvent these potential problems, demographic aspects and absolute estimates of seed output on a per individual basis should be examined in addition to the customarily employed fruit and seed set measures.