seed set

Chromosome numbers and meiotic behavior are reported for the climbing cacti species Hylocereus undatus, Hylocereus polyrhizus, and Selenicereus megalanthus. The Hylocereus spp. are diploid (2n ϭ 22), while S. megalanthus is a tetraploid (2n ϭ 44). Irregular chromosome disjunction at anaphase I in pollen mother cells of S. megalanthus is probably the major cause of its reduced pollen viability and may contribute to low seed set, low number of viable seeds and, consequently, low fruit mass. A pollination study confirmed self-incompatibility in H. polyrhizus and a weakened incompatibility reaction in H. undatus and S. megalanthus. Major crossability barriers do not exist between the Hylocereus spp. investigated. Reciprocal intergeneric crosses were successful between Hylocereus spp. and S. megalanthus, suggesting that an Hylocereus sp. might be one of the diploid progenitors of the tetraploid S. megalanthus. The implications of the results on cacti nomenclature and systematics are briefly discussed.

Abstract: In the context of influence propagation in a social graph, we can identify three orthogonal dimensions-the number of seed nodes activated at the beginning (known as budget), the expected number of activated nodes at the end of the propagation (known as expected spread or coverage), and the time taken for the propagation. We can constrain one or two of these and try to optimize the third. In their seminal paper, Kempe et al. constrained the budget, left time unconstrained, and maximized the coverage: this problem is known ...

Crosses between genetically close and distant populations of Dalechampia scandens (Euphorbiaceae) were made to test whether the responses of various fitness components and measurements of developmental stability were affected by the outcrossing distance (level of outbreeding). Two fecundity traits, seed set and seed mass, decreased consistently with increasing level of outbreeding, and hybrids between the most divergent populations were sterile. Effects of the genetic distance between parental populations on viability traits, survival and vigor at 1 month of age, were highly idiosyncratic. Hybrids of one long-distance combination had no reduction in survival and vigor, while both traits were greatly reduced in the other long-distance combination. The expression of outbreeding depression on fecundity traits differed between reciprocal crosses in some hybrids but not others; thus, hybrid breakdown may have been due to cytoplasmic-by-nuclear gene interactions, reduced endosperm formation, or an interaction between progeny and maternal genotype. None of the measures of developmental stability had a consistent relationship with either genetic distance between parental populations or seedling vigor. These results suggest that fecundity and viability traits may be differentially affected by hybridization, probably due to differences in genetic architecture among populations. This study also confirms that developmental stability, as measured by the level of fluctuating asymmetry, is not a reliable index of genetic stress.

Delayed self-pollination is a mechanism that allows animal-pollinated plants to outcross while ensuring seed production in the absence of pollinators. This study aims to explore a new mechanism of delayed self-pollination facilitated by wind-driven corolla abscission in Incarvillea sinensis var. sinensis. Floral morphology and development, and the process of delayed self-pollination were surveyed. Experiments dealing with pollinator and wind exclusion, pollination manipulations, and pollinator observations were conducted in the field. Delayed self-pollination occurs when the abscising corolla driven by wind drags the adherent epipetalous stamens, thus leading to contact of anthers with stigma in late anthesis. There is no dichogamy and self-incompatibility in this species. The significantly higher proportion of abscised corolla under natural conditions as compared with that in wind-excluding tents indicates the importance of wind in corolla abscission. When pollinators were excluded...

Plants that live in fragmented landscapes, where populations are isolated from each other and in which long-distance dispersal is essential for colonization of empty sites, reproduction should be favoured by self-compatibility (Baker's law). Nevertheless, outcrossing mechanisms, such as self-incompatibility and dichogamy, are common in many species and are often maintained by inbreeding depression in the fitness of selfed progeny. Here, we studied the breeding system and the consequences of selfing and sister mating in Campanula thyrsoides, a short-lived perennial monocarp, which is found in the naturally fragmented landscape of the Alps. An experiment with controlled pollinations was set up in the common garden with plants grown from seeds originating from 14 seed families, collected in the siliceous Central Alps, where this plant is found on isolated carbonate bearing outcrops. Our results indicate that C. thyrsoides has a strong self-incompatibility system (SI) with no or low seed set in selfed flowers compared to outcrossed and sister-crossed flowers. Moreover, the SI system in C. thyrsoides did not break down with flower age as in some other Campanula species. Surprisingly, there was no significant difference in seed set, seed weight, germination percentage, seedling survival and size between outcrossed and sister-crossed offspring, which indicates no inbreeding depression. We suggest that the absence of inbreeding depression in this outcrossing species might be a result of frequent bottlenecks during colonization of the isolated habitats in the alpine landscape.

Most chickpea cultivars grown in regions where temperatures fall below 108C continue to flower but fail to set pods. Research was conducted to characterize cold stress in a subtropical northern Indian location, Hisar and to examine genetic variation in pod and seed set at low temperatures. Lines of various maturity groups were used so that phenological timing of stress differed with line. Flowering was therefore synchronized with a cold spell to evaluate tolerance. A substantial variation was found both in field and controlled environments. Two early maturing advanced breeding lines, ICCVs Ž . ICCVs ICRISAT Chickpea Variety 88502 and 88503, showed good pod set in cold spells, but seed growth in them was limited. Evaluation of the parents indicated possible contribution of a germplasm from the former Soviet Union, K 1189 Ž . ICRISAT chickpea germplasm collection No ICC 8923 , to cold tolerance. Based on experiments in controlled environ-Ž . Ž . ments, it is suggested that a pod set can occur at night temperatures of 0-58C if daytime temperatures exceed 208C b seed Ž . Ž . development requires a higher threshold temperature than pod set and c 15r5 and 15r08C dayrnight thermal regimes are useful in preliminary screening of germplasm lines for cold tolerance.

Adventitious shoots were regenerated from in vitro cultured cotyledon and hypocotyl explants excised from one week old seedlings of Plantago afra on MS medium containing various concentrations of BAP + NAA, BAP + IBA, Kinetin + IBA and TDZ+IBA. Multiple shoot regeneration was observed from both explants with the highest shoot regeneration per explant (23.17) on MS medium containing 0.91 μM TDZ - 0.98 μM IBA from hypocotyls. Shoots regenerated on MS medium containing 0.91 μM TDZ - 0.98 μM IBA were best rooted on MS medium containing 3.22 μM NAA. Rooted plantlets were transferred to soil, acclimatized and transferred to the greenhouse for flowering and seed set.

India ranks first both as producer and consumer of pulses. It is also the largest importer of pulses as the total domestic requirement outweighs total production. So, to attain self-sufficiency in terms of pulse production the constraints in cultivation need to be addressed. Pulse production faces a series of constraints which include its inherent physiological limitations. These limitations include lower germination percentage, source limitation, low leaf area development, indeterminate growth habit, C3 photosynthetic apparatus, slow initial dry matter accumulation, limited photosynthesis, hormones inhibitors, decline in nodule activity and diversion of metabolic energy to sinks for protein synthesis. To overcome these limitations simple agronomic techniques such as application of growth hormones are adopted. This paper critically reviews the physiological constraints of pulses and effect of growth regulators to improve these limitations and concomitantly increasing yield.

The relationships between Philodendron solimoesense and the larvae of two chalcid wasp species, inhabiting up to 88% of the infructescences, were studied in French Guiana. Exurus sp. (Chalcidoidea, Eulophidae, Tetrastichinae), is a gall maker and its larvae develop at the expense of seeds which are transformed into galls. We estimate that two seeds are necessary for the development of one eulophid. Their impact on plant reproductive success appears to be important, since parasitized fruits produce 60% fewer seeds than nonparasitized fruits and could explain the reduced seed set observed (53%). The larvae of a Sycophila sp. (Chalcidoidea, Eurytomidae, Eurytominae) are also present in the fruits of P. solimoesense occupied by eulophid larvae. The eurytomid larvae apparently develop at the expense of about one eulophid and are responsible for the death of 39% of them by direct predation or indirectly by consuming the gall tissues. Eulophids are far more abundant than eurytomids, since parasitized fruits contain an average of 11 eulophids but only one eurytomid. As chalcid wasp emergence takes place in a closed cavity and sex ratios are strongly biased in a given gall, local mate competition may occur as observed for fig wasps within figs.

A T-DNA insertional mutant OsAPC6 of rice, with gibberellic acid insensitivity and reduced height, had up to 45% reduced seed set. The insertion occurred on chromosome 3 of rice in the gene encoding one of the subunits of anaphase promoting complex/Cyclosome APC6. The primary mother cells of the mutant plants had normal meiosis, male gametophyte development and pollen viability. Confocal laser scanning microscopic (CLSM) studies of megagametophyte development showed abnormal mitotic divisions with reduced number or total absence of polar nuclei in about 30-35% megagametophytes of OsAPC6 mutant leading to failure of endosperm and hence embryo and seed development. Abnormal female gametophyte development, high sterility and segregation of tall and gibberellic acid sensitive plants without selectable marker Hpt in the selfed progeny of OsAPC6 mutant plants indicate that the mutant could be maintained in heterozygous condition. The abnormal mitotic divisions during megagametogenesis could be attributed to the inactivation of the APC6/CDC16 of anaphase promoting complex of rice responsible for cell cycle progression during megagametogenesis. Functional validation of the candidate gene through transcriptome profiling and RNAi is in progress.

We reprove a result of Dehkordi, Frati, and Gudmundsson: every two vertices in a non-obtuse triangulation of a point set are connected by an angle-monotone pathan xy-monotone path in an appropriately rotated coordinate system. We show that this result cannot be extended to angle-monotone spanning trees, but can be extended to boundary-rooted spanning forests. The latter leads to a conjectural edge-unfolding of sufficiently shallow polyhedral convex caps.

Terakreditasi B berdasarkan Keputusan Dirjen Dikti Depdiknas RI No. 26/DIKTI/Kep./2005 I88N 0215 -4706 lor1bun~o Floribunda merupakan organ resmi Pengga1ang Taksonomi Tumbuhan Indonesia, diterbitkan dua ka1i setahun dan menerbitkan maka1ah da1am bahasa Indonesia dan lnggris mengenai pe1bagai gatra sistematika keanekaragaman flora Ma1esia pada umumnya dan Indonesia pada khususnya yang berasa1 dari hasi1 pene1itian, pengamatan 1apangan, penga1aman pribadi, te1aahan bergagasan, dan tinjauan kritis. Sidang Penyunting Ketua Penyunting Tutie Djarwaningsih (BO) Penyunting Tri Mu1yaningsih (UNRAM) Atik Retnowati (BO) Novita Kartika Indah (UNESA) Titien N. Praptosuwiryo (KRI) Nunik Sri Ariyanti (IPB) Penyunting Pelaksana Himmah Rustiami (BO) Tata Letak Muhamad Rus1an (BO) Petunjuk kepada pengarang Maka1ah 1engkap memuat hasi1 penelitian floristik, revisi, atau monografi unsur-unsur flora Malesia. Komunikasi pendek mencakup laporan kemajuan kegiatan penelitian, pengembangan dan rekayasa keanekaragaman flora Malesia yang perlu segera dikomunikasikan. Tulisan lain meliputi obituari tokoh keanekaragaman flora, tinjauan kritis bergagasan, telaahan serta pembahasan persoalan aktual seputar kegiatan penelitian, pengembangan dan rekayasa tetumbuhan Indonesia, serta timbangan buku akan dimuat berdasarkan undangan.

Terakreditasi B berdasarkan Keputusan Dirjen Dikti Depdiknas RI No. 26/DIKTI/Kep./2005 I88N 0215 -4706 lor1bun~o Floribunda merupakan organ resmi Pengga1ang Taksonomi Tumbuhan Indonesia, diterbitkan dua ka1i setahun dan menerbitkan maka1ah da1am bahasa Indonesia dan lnggris mengenai pe1bagai gatra sistematika keanekaragaman flora Ma1esia pada umumnya dan Indonesia pada khususnya yang berasa1 dari hasi1 pene1itian, pengamatan 1apangan, penga1aman pribadi, te1aahan bergagasan, dan tinjauan kritis. Sidang Penyunting Ketua Penyunting Tutie Djarwaningsih (BO) Penyunting Tri Mu1yaningsih (UNRAM) Atik Retnowati (BO) Novita Kartika Indah (UNESA) Titien N. Praptosuwiryo (KRI) Nunik Sri Ariyanti (IPB) Penyunting Pelaksana Himmah Rustiami (BO) Tata Letak Muhamad Rus1an (BO) Petunjuk kepada pengarang Maka1ah 1engkap memuat hasi1 penelitian floristik, revisi, atau monografi unsur-unsur flora Malesia. Komunikasi pendek mencakup laporan kemajuan kegiatan penelitian, pengembangan dan rekayasa keanekaragaman flora Malesia yang perlu segera dikomunikasikan. Tulisan lain meliputi obituari tokoh keanekaragaman flora, tinjauan kritis bergagasan, telaahan serta pembahasan persoalan aktual seputar kegiatan penelitian, pengembangan dan rekayasa tetumbuhan Indonesia, serta timbangan buku akan dimuat berdasarkan undangan.

Background: Early flowering stages with low temperatures (0 to 10  C) may also result in increased floral abortion, which lowers pod and seed set. Both the duration and rate of grain filling are sensitive to temperature changes and high temperatures may reduce productivity due to decreased flowering, pod formation and seed set, which could result in a loss of output. To mitigate the effects of high or low temperatures on chickpea productivity, it is crucial to investigate pollen traits, including pollen fertility, sterility, germination, tube length and diameter. Methods: The field experiments were conducted at Main Agricultural Research Station (MARS), University of Agricultural Sciences (UAS), Dharwad during rabi 2018-19 and 2019-20 using six chickpea genotypes with three replications. Sowing dates i.e., Early sown (40 th Standard Meteorological Week i.e., 5 th October), normal sown (45 th Standard Meteorological Week i.e., 5 th November) and late sown (49 th Standard Meteorological Week i.e., 5 th December) of rabi season during 2018-19 and 2019-20 were manipulated in order to create the effects of high temperature. Result: Early-sown chickpea genotypes (planted in October) experienced low-temperature stress, while late-sown genotypes (planted in December) were subjected to high-temperature stress. The late sowing period led to poor performance due to high-temperature exposure, negatively impacting flowering, pod formation and seed set, ultimately lowering the productivity of the chickpea crops. Among the genotypes, positive correlation was seen between maximum temperature and pollen tube length and sterile pollen diameter during 2018-19 (0.770**, 0.545*) and 2019-20 (0.548*, 0.542*) and the averag e of two years (0.543**, 0.633**), respectively in JAKI 9218 genotype. This relationship was consistent across both years of the study (2018-19 and 2019-20), indicating that increased temperatures may influence pollen fertility and sterility, thereby affecting chickpea productivity.

Original Research Article White fonio (Digitaria exilis Stapf), a neglected crop in West African countries, is considered as a strategic source for nutrition and food security and a potential source to generate significant financial returns for farmers. Fonio has agronomic potentialities and adaptation to drought conditions that make it deserve special attention as well as its wild relatives which have interesting genetic traits for its improvement. The objective of this study was to evaluate the relationship between white fonio and its wild relatives based on agro-morphological traits and SSR markers. A total of 25 accessions belonging to 10 species and provided from the Herbaria of DAKAR and IFAN and from our collections were analyzed. Morphological and SSR similarity between species was calculated and the correlation between morphological and genetic variation was analyzed by the Mantel test. The results showed three main classes for each method used and a closely relationship be...

Ovule fertilization and seed set were investigated in Crocus thomasii and Crocus vernus subsp, vernus, after different matings. The results gave evidence for a strict ovarian barrier in C. thomasii, which prevents self-fertilization either in self-or mixed-and doublepollination. In C. vernus the ovarian barrier to selfing is not so effective, but a further incompatibility reaction is expressed after self-fertilization resulting in a complete failure of embryogenesis. The implications of the present observations in respect to the mechanisms of pregamic-and postgamic rejection, indicate that a gametophytic system of self-incompatibility controls the ovule fertilization, and a not yet defined system of self-incompatibility controls embryogenesis.

The reproductive system was studied in Crocus genus (Iridaceae) following intra-and interspecific pollination, by using light and scanning electron microscopy. The results suggest that the stigma-style tract of the Crocus pistil is a mere promoter of pollen tube growth, while intra-and interspecific discrimination of compatible and incompatible pollen occurs in the ovarian tract. Here, the transmitting tissue consists of special epidermal cells, whose granular or floccular secretions provide the selective medium for the growth of pollen tubes. The ovarian self-incompatibility (SI) is widespread within the genus, resulting in a partial or complete suppression of self-fertilization. Moreover, postzygotic SI mechanisms, as well as postzygotic mechanisms of unknown nature, seem to be recurrent and both are responsible for seed abortion. The interspecific ovarian incompatibility concerns only unrelated crosses; crosses between related fertile species succeed both in fertilization and seed-set.

A survey was undertaken to determine the pest status of herbivorous blister beetles, Hycleus spp., in western Kenya where they attack crops such as Desmodium spp., other leguminous plants and sweetpotato. Desmodium spp. are important intercrops in the 'push-pull'' strategy adopted for Striga and stemborer control in maize and sorghum. Production of desmodium seed is adversely affected by blister beetles, which feed on the flowers and negatively affect seed setting. To assess farmers' knowledge and perceptions of Hycleus spp. as pests, a questionnaire survey was conducted in three sites in Bungoma district, western Kenya, in 2007. The survey was followed by field sampling of Desmodium spp. and sweetpotato to compare the results with the responses received from farmers. Hycleus spp. were mentioned by 75% of the respondents as major pests of Desmodium spp. During field sampling Hycleus spp. comprised 70% of the insect pests collected. According to farmers, blister beetles were more abundant on desmodium than on sweetpotato. However, field sampling revealed that differences in beetle abundance on the two crops were not consistent across different sites, suggesting that these crops may function as alternative hosts. The study provides baseline information for the development of a management strategy for blister beetles.

Spartina alterniflora (Loisel.), smooth cordgrass, is a dominant perennial salt marshgrass native to tidal wetland plant communities along the Atlantic and Gulf coasts of North America. It is an important plant species for coastal reclamation and restoration efforts. It spreads quickly by rhizomes and tolerates a wide range of saline, anoxic, and sulfidic soils. However, because of poor seed production this species is propagated vegetatively for reclamation or restoration projects. Current practices reduce genetic diversity of the species by utilizing a single vegetatively propagated genotype. The objectives of this study were; 1) identify multiple genotypes of S. alterniflora for use in restoration efforts and 2) assess genetic variability of these genotypes at the molecular level. Identification of desirable plants was based on plant growth characteristics and reproductive traits. Growth characters were plant height, spread, rust reaction, and vigor. Reproductive traits were seed set, germination, kernel weight, seed weight, and total seed per plant. This process resulted in seven plants, descended from seven different original source populations, which demonstrated superior performance for vegetative and reproductive traits. Molecular marker analysis revealed that genetic diversity, essential for success in the restoration projects, was maintained in selected plants. These plants offer an enhanced germplasm base for current restoration efforts. Research is continuing on the feasibility of developing seed based populations that would add even greater genetic diversity to the current accepted restoration practices.

Climate change is likely to alter both flowering phenology and water availability for plants. Either of these changes alone can affect pollinator visitation and plant reproductive success. The relative impacts of phenology and water, and whether they interact in their impacts on plant reproductive success remain, however, largely unexplored. We manipulated flowering phenology and soil moisture in a factorial experiment with the subalpine perennialMertensia ciliata(Boraginaceae). We examined responses of floral traits, floral abundance, pollinator visitation, and composition of visits by bumblebees vs. other pollinators. To determine the net effects on plant reproductive success, we also measured seed production and seed mass. Reduced water led to shorter, narrower flowers that produced less nectar. Late flowering plants produced fewer and shorter flowers. Both flowering phenology and water availability influenced pollination and reproductive success. Differences in flowering phenolo...

In order to determine the impact of polyamines on the yield-related parameters of rice (Oryza sativa L.) exposed to NaCl, the plants belonging to a salt-sensitive cultivar I Kong Pao were maintained from the young seedling stage until harvest on nutrient solutions containing 0 or 30 mM NaCl in the presence or absence of 10 lM putrescine (Put), 10 lM spermidine (Spd) or 10 lM spermine (Spm). Exogenous Put and to a lesser extent exogenous Spd improved growth and yield of salt-treated plants in relation to an increase in K + /Na + ratio of shoots and roots as compared to plants exposed to NaCl in the absence of exogenous polyamines. Exogenous Put also improved the net CO 2 assimilation, at least partly as a consequence of an increase in the stomatal conductance. Yield increase of salttreated plants exposed to Put was related to an improvement of floral morphogenesis leading to a higher number of fertile tillers per plant and a higher number of spikelets per panicle. Putrescine also improved the pollen viability in salt-treated plants, allowing a higher seed set and thus a higher grain yield per plant. Although polyamines accumulated in the shoots to some extent in response to exogenous application, neither Put nor Spd accumulated in the seeds. In contrast, Spm did not afford any protection of salt-treated plants but was translocated to the seeds during maturation. Seeds with a high internal Spm concentration exhibited delayed germination in the presence of NaCl. These data are discussed in relation to the implication of polyamine in the metabolism and physiology of salt-treated plants.

In order to determine the impact of polyamines on the yield-related parameters of rice (Oryza sativa L.) exposed to NaCl, the plants belonging to a salt-sensitive cultivar I Kong Pao were maintained from the young seedling stage until harvest on nutrient solutions containing 0 or 30 mM NaCl in the presence or absence of 10 lM putrescine (Put), 10 lM spermidine (Spd) or 10 lM spermine (Spm). Exogenous Put and to a lesser extent exogenous Spd improved growth and yield of salt-treated plants in relation to an increase in K + /Na + ratio of shoots and roots as compared to plants exposed to NaCl in the absence of exogenous polyamines. Exogenous Put also improved the net CO 2 assimilation, at least partly as a consequence of an increase in the stomatal conductance. Yield increase of salttreated plants exposed to Put was related to an improvement of floral morphogenesis leading to a higher number of fertile tillers per plant and a higher number of spikelets per panicle. Putrescine also improved the pollen viability in salt-treated plants, allowing a higher seed set and thus a higher grain yield per plant. Although polyamines accumulated in the shoots to some extent in response to exogenous application, neither Put nor Spd accumulated in the seeds. In contrast, Spm did not afford any protection of salt-treated plants but was translocated to the seeds during maturation. Seeds with a high internal Spm concentration exhibited delayed germination in the presence of NaCl. These data are discussed in relation to the implication of polyamine in the metabolism and physiology of salt-treated plants.

Grain yields in buckwheat (Fagopyrum esculentum) are consistently low despite a profuse and long‐lasting flowering. The mechanisms underlying this reproductive failure are still largely unknown. In this study, performed in strictly controlled conditions, the possible implication of assimilate availability in the regulation of the reproductive development was investigated in the ‘La Harpe’ cultivar, by manipulating sink/source relationships through excisions of selected leaves and/or selected inflorescences and hand pollinations of selected and precisely identified flowers. Increasing or decreasing source/sink organ ratio in buckwheat, respectively, enhanced or reduced the production of racemes by the shoot apical meristem and of cymes by the racemes, ultimately modulating the number of flowers per plant. The effect on seed production was essentially indirect and related to flower production. Seeds developing on a plant also affected reproductive morphogenesis, limiting flower produc...

A survey was undertaken to determine the pest status of herbivorous blister beetles, Hycleus spp., in western Kenya where they attack crops such as Desmodium spp., other leguminous plants and sweetpotato. Desmodium spp. are important intercrops in the 'push-pull'' strategy adopted for Striga and stemborer control in maize and sorghum. Production of desmodium seed is adversely affected by blister beetles, which feed on the flowers and negatively affect seed setting. To assess farmers' knowledge and perceptions of Hycleus spp. as pests, a questionnaire survey was conducted in three sites in Bungoma district, western Kenya, in 2007. The survey was followed by field sampling of Desmodium spp. and sweetpotato to compare the results with the responses received from farmers. Hycleus spp. were mentioned by 75% of the respondents as major pests of Desmodium spp. During field sampling Hycleus spp. comprised 70% of the insect pests collected. According to farmers, blister beetles were more abundant on desmodium than on sweetpotato. However, field sampling revealed that differences in beetle abundance on the two crops were not consistent across different sites, suggesting that these crops may function as alternative hosts. The study provides baseline information for the development of a management strategy for blister beetles.

Given a simple polygon $ \mathcal {P} $ of $ n $ vertices in the Plane. We study the problem of computing the visibility area from a given viewpoint $ q $ inside $ \mathcal {P} $ where only sub-linear variables are allowed for working space. Without any memory-constrained, this problem was previously solved in $ O(n) $-time and $ O(n) $-variables space. In a newer research, the visibility area of a point be computed in $ O(n) $-time, using $ O(\sqrt{n}) $ variables for working space. In this paper, we present an optimal-time algorithm, using $ O(c/\log n) $ variables space for computing visibility area, where $ c<n $ is the number of critical vertices. We keep the algorithm in the linear-time and reduce space as much as possible.

The paper provides new information about the distribution and conservation status of three rare spring geophytes in Bosnia and Herzegovina: Fritillaria meleagris, Gagea spathacea and Leucojum vernum. New records, along with data from literature and/or herbarium studies, are presented with distribution maps of 10×10 km UTM grid. Information about the habitat, soil and population size for each record was also given. The IUCN threat status category for Bosnia and Herzegovina was estimated for F. meleagris, and reassessed for G. spathacea and L. vernum.

The purpose of the research was to estimate the efficiency of pollination by bees of some parental sunflower varieties, depending on the distance between the selected sectors with inflorescences and hives with bees, placed for pollination, was carried out. The experiments were performed on a field of sunflowers, with an area of 36 ha, where maternal variety "Express" and paternal variety "NS-X 6006" (both from Republic of Serbia), destined for crossing to obtain hybrid seeds, were sown alternatively. Around chain have been located 144 bee families, so that there were 4 families per ha. For verifying the self-pollination capacity of sunflower, 4 experimental sectors were selected, at different distances from the beehives 10, 100, 300 and 500 m. As a control 8 inflorescences were selected in each sector, which before flowering, were covered with gauze. In the phase of full ripening of seeds, from each experimental sector the seeds were collected manually 8 control-...

Let S be a set of n > 2 points in the plane whose convex hull has perimeter t. Given a number P ≥ t, we study the following problem: Of all curves of perimeter P that enclose S, which is the curve that encloses the maximum area? In this paper, we give a complete characterization of this curve. We show that there are cases where this curve cannot be computed exactly and provide an O(n logn)-time algorithm to obtain an approximation of this curve, with arbitrary precision, having the same combinatorial structure.

We consider guarding classes of simple polygons using mobile guards (polygon edges and diagonals) under the constraint that no two guards may see each other. In contrast to most other art gallery problems, existence is the primary question: does a specific type of polygon admit some guard set? Types include simple polygons and the subclasses of orthogonal, monotone, and starshaped polygons. Additionally, guards may either exclude or include the endpoints (so-called open and closed guards). We provide a nearly complete set of answers to existence questions of open and closed edge, diagonal, and mobile guards in simple, orthogonal, monotone, and starshaped polygons, with some surprising results. For instance, every monotone or starshaped polygon can be guarded using hidden open mobile (edge or diagonal) guards, but not necessarily with hidden open edge or hidden open diagonal guards.

Given a planar straight-line graph G = (V, E) in R 2 , a circumscribing polygon of G is a simple polygon P whose vertex set is V , and every edge in E is either an edge or an internal diagonal of P . A circumscribing polygon is a polygonization for G if every edge in E is an edge of P . We prove that every arrangement of n disjoint line segments in the plane has a subset of size Ω( √ n) that admits a circumscribing polygon, which is the first improvement on this bound in 20 years. We explore relations between circumscribing polygons and other problems in combinatorial geometry, and generalizations to R 3 . We show that it is NP-complete to decide whether a given graph G admits a circumscribing polygon, even if G is 2-regular. Settling a 30-year old conjecture by Rappaport, we also show that it is NP-complete to determine whether a geometric matching admits a polygonization.

Let S = {p1, p2, . . . , pn} be a set of pairwise disjoint geometric objects of some type in a 2D plane and let C = {c1, c2, . . . , cn} be a set of closed objects of some type in the same plane with the property that each element in C covers exactly one element in S and any two elements in C are interior-disjoint. We call an element in S a seed and an element in C a cover. A cover contact graph (CCG) has a vertex for each element of C and an edge between two vertices whenever the corresponding cover elements touch. It is known how to construct, for any given point seed set, a disk or triangle cover whose contact graph is 1or 2-connected but the problem of deciding whether a k-connected CCG can be constructed or not for k > 2 is still unsolved. A triangle cover contact graph (T CCG) is a cover contact graph whose cover elements are triangles. In this paper, we give algorithms to construct a 3-connected T CCG and a 4-connected T CCG for a given set of point seeds. We also show that any connected outerplanar graph has a realization as a T CCG on a given set of collinear point seeds. Note that, under this restriction, only trees and cycles are known to be realizable as CCG.

Orri' is a new Israeli mandarin variety, selected for seedlessness and low pollen grain viability from irradiated bud wood of the cultivar 'Orah' mandarin [Temple (Citrus temple hort. ex Y. Tanaka) Â Dancy (Citrus tangerina hort. ex Tanaka)] . In the north of Israel the 'Orri' fruits mature in February and March; they have a delicious taste, the peel is deep orange in color and easy to remove, and the fruit has few or no seeds, i.e., 0-4 seeds per fruit. The first commercial 'Orri' plantation was established in 1996, and with passing time it became one of the main mandarin plantations in Israel. However, the Israeli 'Orri' suffers from inadequate yield, and so far no published studies have addressed this problem. In the present study we determined the influence of the pollenizer on 'Orri' seediness and fertility, i.e., number of seeds per fruit, total yield, number of fruits per tree and fruit size.

ABSTRACTWe quantified the fruit set of four Acacia spp. inside and outside of long‐term experimental exclosures in order to examine the fitness consequences of herbivory by large mammals. We found a considerable interspecific variation in the reproductive fitness costs of herbivory in four African Acacia spp. Acacia nilotica and A. brevispica respond to protection from large mammalian herbivores by greatly increasing their seed set. In contrast, there was little or no increase in seed set in A. mellifera and A. etbaica. The reasons for these differences are not known, but may be related to armament morphologies.

The greedy triangulation of a finite planar point set is obtained by repeatedly inserting a shortest diagonal that does not cross those already in the plane. The Delaunay triangulation, which is the straight-line dual of the Voronoi diagram, can be produced in O(n log n) worst-case time, and often even faster, by several practical algorithms. In this paper we show that for any planar point set S, if the Delaunay triangulation of S is given, then the greedy triangulation of S can be computed in linear worst-case time (and linear space).

In Pongamia pinnata only one of the two ovules develops into a seed in most of the pods. Since pollen was not found to be limiting and reduced fertilization could not completely explain the observed frequency of seed abortion, it implied an effect of postfertilization factors. Aqueous extracts of developing seeds and maternal tissue (placenta) did not influence abortion in vitro, suggesting that abortion may not be mediated by a chemical. Experimental uptake of 14C sucrose in vitro indicated that both the stigmatic and the peduncular seed have similar inherent capacities of drawing resources, but the peduncular seed is deprived of resources in the presence of the stigmatic seed. This deprivation of the peduncular seed could be offset by supplying an excess of hormones leading to the subsequent formation of two seeds in a pod. The prevalence of single‐seeded pods in P. pinnata seems therefore to be a result of competition between the two seeds for maternal resources. The evolutionary...

Effects of local density on insect visitation and fertilization success in the narrow-endemic Centaurea corymbosa (Asteraceae). Á/ Oikos 111: 130 Á/142. Plant population size and density can influence the interactions between plants and pollinators, and affect plant reproductive success. We investigated the effects of local conspecific density on insect visitation and fertilization success in the rare, cliffdwelling, self-incompatible Centaurea corymbosa , in which fecundity plays a key role in variation in population growth rate among years and among the six extant populations. Plant size, capitulum size, the abundance of co-flowering species, and the weather conditions were added as covariates in the analyses. Over three populations and two years (1995 and 2002), fertilization rate was positively related to the number of flowering conspecifics within 10 m. Fertilization rate varied among populations, but this variation over all six populations in 2002 could not be attributed to differences in population size. Observations in one population in 2003 showed that there was no difference in insect visitation per capitulum between plants in sparse vs dense patches whilst plants from sparse patches suffered reduced fertilization rate. Visitation and fertilization rates were not affected by plant size and the abundance of co-flowering species, but weather conditions at the time of flowering had a strong effect on both variables. Capitulum size had a positive effect on visitation rate, but an effect on fertilization rate only in 1995 and 2002 and not in 2003. Our results suggest that pollen limitation affects fertilization rate in C. corymbosa due to limited compatible mate availability rather than pollinator limitation. They agree with previous genetic results derived from paternity analysis. Whether or not the benefits of local spatial agregation to reproductive success result in increased individual fitness will depend on the relative reduction in survival of vegetative stages due to intra-specific competition.

Plant population size and density can influence the interactions between plants and pollinators, and affect plant reproductive success. We investigated the effects of local conspecific density on insect visitation and fertilization success in the rare, cliffdwelling, self-incompatible Centaurea corymbosa , in which fecundity plays a key role in variation in population growth rate among years and among the six extant populations. Plant size, capitulum size, the abundance of co-flowering species, and the weather conditions were added as covariates in the analyses. Over three populations and two years (1995 and 2002), fertilization rate was positively related to the number of flowering conspecifics within 10 m. Fertilization rate varied among populations, but this variation over all six populations in 2002 could not be attributed to differences in population size. Observations in one population in 2003 showed that there was no difference in insect visitation per capitulum between plants in sparse vs dense patches whilst plants from sparse patches suffered reduced fertilization rate. Visitation and fertilization rates were not affected by plant size and the abundance of co-flowering species, but weather conditions at the time of flowering had a strong effect on both variables. Capitulum size had a positive effect on visitation rate, but an effect on fertilization rate only in 1995 and 2002 and not in 2003. Our results suggest that pollen limitation affects fertilization rate in C. corymbosa due to limited compatible mate availability rather than pollinator limitation. They agree with previous genetic results derived from paternity analysis. Whether or not the benefits of local spatial agregation to reproductive success result in increased individual fitness will depend on the relative reduction in survival of vegetative stages due to intra-specific competition.

Plant population size and density can influence the interactions between plants and pollinators, and affect plant reproductive success. We investigated the effects of local conspecific density on insect visitation and fertilization success in the rare, cliffdwelling, self-incompatible Centaurea corymbosa , in which fecundity plays a key role in variation in population growth rate among years and among the six extant populations. Plant size, capitulum size, the abundance of co-flowering species, and the weather conditions were added as covariates in the analyses. Over three populations and two years (1995 and 2002), fertilization rate was positively related to the number of flowering conspecifics within 10 m. Fertilization rate varied among populations, but this variation over all six populations in 2002 could not be attributed to differences in population size. Observations in one population in 2003 showed that there was no difference in insect visitation per capitulum between plants in sparse vs dense patches whilst plants from sparse patches suffered reduced fertilization rate. Visitation and fertilization rates were not affected by plant size and the abundance of co-flowering species, but weather conditions at the time of flowering had a strong effect on both variables. Capitulum size had a positive effect on visitation rate, but an effect on fertilization rate only in 1995 and 2002 and not in 2003. Our results suggest that pollen limitation affects fertilization rate in C. corymbosa due to limited compatible mate availability rather than pollinator limitation. They agree with previous genetic results derived from paternity analysis. Whether or not the benefits of local spatial agregation to reproductive success result in increased individual fitness will depend on the relative reduction in survival of vegetative stages due to intra-specific competition.

Analyzing massive social networks challenges both high-performance computers and human under-standing. These massive networks cannot be visualized easily, and their scale makes applying complex analysis methods computationally expensive. We present a region-growing method for finding a smaller, more tractable subgraph, a community, given a few example seed vertices. Unlike existing work, we focus on a small number of seed vertices, from two to a few dozen. We also present the first comparison between five algorithms for ...

Effects of local abundance, in terms of plot size (number of individuals) and purity (relative abundance), on pollination interactions were studied by examining the quantity and quality of pollinator services and subsequent seed set in the narrow endemic, endangered and self-compatible species Delphinium bolosii. The most frequent visitors were Lepidoptera (mainly Macroglossum stellatarum and two species of Gonopteryx) and Hymenoptera (small bees). Differences in relative frequency of visits to plants were observed between populations, possibly due to the intrinsic local insect fauna. Plots with high numbers of individuals attracted more pollinators, so plants from these plots were visited more often. At the individual level, no effect of size was detected but visitation rates were significantly different between the two studied populations. The same pattern was observed for stigmatic pollen loads and seed set. The effects of purity were assessed by comparing pure plots of D. bolosii with a mixed plot that also included the neighbor species Rubus ulmifolius, an invasive shrub. Although interspecific competition for pollinator visits was observed, conspecific pollen deposition did not vary between pure and mixed plots. However, negative effects on reproductive traits such as higher rates of seed abortion (50%) and a lower S/O index (viable seeds/ovules) were detected in individuals from the mixed plot. These results may be helpful for developing conservation measures, especially in one of the populations, where R. ulmifolius is abundant due to nearby abandoned agricultural land.

To my wife, my parents, my son Elyas and daughters Islam and Safeea, for their sacrifices, prayers, and constant support and encouragement. iii DECLARATION I declare that this thesis submitted is wholly my own work unless otherwise referenced or acknowledged. The document has not been submitted for qualifications at any other academic institution.

In each of two populations of outcrossing Mimulus guttatus and selfing M. micranthus we quantified genetic variation for floral traits which previously were shown to be associated with mating system evolution in this genus at both the population and species levels. Both broad-and narrow-sense heritabilities and genetic correlations were measured in greenhouse experiments. For one population of M. guttatus, we investigated and found significant among family variation for autogamous seed-set in a pollinator-free environment, and this was weakly associated with stigma-anther separation. We observed intermediate to high levels of broad-and narrow-sense heritabilities for all traits, but genetic variation was consistently lower in the selfing species. Although characters correlated to stigma-anther separation or to day of first flower varied between populations and between taxa, there were consistently strong positive genetic correlations among traits associated with floral size.

In this study we investigated the genetic determinism of criteria suitable for breeding for seed yield and yield stability in dry pea (Pisum sativum L.) using a diallel cross involving eight genotypes. Seven criteria related to plant and seed development were evaluated including: onset of flowering, node of first flower, leaf appearance rate, rate of progression of flowering, number of podded nodes on the main stem, mean dry seed weight per podded node and number of basal branches per plant. Most of these traits measured are related to timing of seed set and are thought to be critical in determining yield stability. We combined different diallel analyses (Hayman, 1954; Griffing, 1956) with a Principal Component Analysis, to divide the parental lines into groups sharing similar genetic control for the traits studied. We found that the two main groups, defined according to their genetic control of node of first flower, also differed for all the others characters and, in particular, did not reach the same levels of productivity. These results indicated that crosses within the group with the highest productivity, but between lines with differing development and architectural features, could be a good starting point for breeding high-yield pure lines.

Most coevolving relationships between pairs of species are embedded in a broader multispecific interaction network. The mutualistic interaction between Lithophragma parviflorum (Saxifragaceae) and its pollinating floral parasite Greya politella (Lepidoptera, Prodoxidae) occurs in some communities as a pairwise set apart from most other interactions in those communities. In other communities, however, this pair of species occurs with congeners and with other floral visitors to Lithophragma. We analyzed local and geographic differences in the network formed by interactions between Lithophragma plants and Greya moths in communities containing two Lithophragma species, two Greya species, and floral visitors other than Greya that visit Lithophragma flowers. Our goal was to evaluate if non-Greya visitors were common, if visitor assembly differs between Lithophragma species and populations and if these visitors act as effective pollinators. Sympatric populations of L. heterophyllum and L. parviflorum differ in floral traits that may affect assemblies of floral visitors. Visitation rates by non-Greya floral visitors were low, and the asymptotic number of visitor species was less than 20 species in all populations. Lithophragma species shared some of the visitors, with visitor assemblages differing between sites more for L. heterophyllum than for L. parviflorum. Pollination efficacy experiments showed that most visitors were poor pollinators. Single visits to flowers by this assemblage of species resulted in significantly higher seed set in Lithophragma heterophyllum (30.6 ± 3.9 SE) than in L. parviflorum (4.7 ± 3.4 SE). This difference was consistent between sites, suggesting that these visitors provide a better fit to the floral morphology of L. heterophyllum. Overall, none of the non-Greya visitors appears to be either sufficiently common or efficient as a pollinator to impose strong selection on any of these four Lithophragma populations in comparison with Greya, which occurs within almost all populations of these species throughout their geographic ranges.

The challenge of similarity search in massive DNA sequence databases has inspired major changes in BLAST-style alignment tools, which accelerate search by inspecting only pairs of sequences sharing a common short "seed," or pattern of matching residues. Some of these changes raise the possibility of improving search performance by probing sequence pairs with several distinct seeds, any one of which is sufficient for a seed match. However, designing a set of seeds to maximize their combined sensitivity to biologically meaningful sequence alignments is computationally difficult, even given recent advances in designing single seeds. This work describes algorithmic improvements to seed design that address the problem of designing a set of n seeds to be used simultaneously. We give a new local search method to optimize the sensitivity of seed sets. The method relies on efficient incremental computation of the probability that an alignment contains a match to a seed π, given that it has already failed to match any of the seeds in a set. We demonstrate experimentally that multi-seed designs, even with relatively few seeds, can be significantly more sensitive than even optimized single-seed designs.