scholarly journals Viewpoints on apornictic and sexual reproduction in angiosperms

2014 ◽  
Vol 50 (1-2) ◽  
pp. 195-199 ◽  
Author(s):  
Sven Asker
Keyword(s):  
Sexual Reproduction ◽  
Reproductive Cycle ◽  
Vegetative Reproduction ◽  
Reproductive Behaviour ◽  
Polygenic Control ◽  
Gametophytic Apomixis

Gametophytic apomixis implies different changes of the reproductive cycle of sexual plants. Each of these "elements of apomixis" occurs in sexual plants, which may even display functional diploid parthenogenesis. Thus, apomixis, like vegetative reproduction, is part of the reproductive behaviour of sexual plants, becoming important when sexual reproduction is impaired. The elements of apomixis are probably to a large extent under polygenic control.

Niche differentiation between two rhizomatous plant species: Typha latifolia and Typha angustifolia

1982 ◽  
Vol 60 (1) ◽  
pp. 46-57 ◽  
Author(s):  
James B. Grace ◽  
Robert G. Wetzel
Keyword(s):  
Sexual Reproduction ◽  
Shallow Water ◽  
Surface Area ◽  
Leaf Surface ◽  
Vegetative Reproduction ◽  
Typha Latifolia ◽  
Morphological Characteristics ◽  
Niche Differentiation ◽  
Typha Angustifolia ◽  
Leaf Surface Area

Morphological characteristics and biomass allocation were examined for two species of Typha in a small pond. Typha latifolia differed from T. angustifolia in having shorter leaf height, wider leaves, greater leaf surface area, greater allocation to leaves, greater number of smaller rhizomes, greater allocation to vegetative reproduction, smaller allocation to sexual reproduction, and fewer number of flowering plants. For both species, those plants growing in deeper water had taller leaves, a greater allocation to leaves, and a decreased allocation to sexual and vegetative reproduction. Previous studies of these populations have demonstrated that these two species are segregated according to water depth with T. latifolia being competitively superior in shallow water (less than 15 cm) but T. angustifolia having the potential to grow in deeper water than T. latifolia. Results from this study indicate that T. latifolia is competitively superior in shallow water because of its greater leaf surface area but that T. angustifolia's tall, narrow leaves and large rhizome storage permit it to grow in deeper water than T. latifolia. The greater amount of sexual reproduction in T. angustifolia is correlated with its more restricted distribution and fugitive nature.

Effect of prolonged vegetative reproduction of olive tree cultivars (Olea europaea L.) in mitochondrial homoplasmy and heteroplasmy

Genome ◽  
2003 ◽  
Vol 46 (3) ◽  
pp. 377-381 ◽  
Author(s):  
Angel García-Díaz ◽  
Ricardo Oya ◽  
Antonio Sánchez ◽  
Francisco Luque
Keyword(s):  
Mitochondrial Genome ◽  
Sexual Reproduction ◽  
Olea Europaea ◽  
Vegetative Reproduction ◽  
Intergenic Spacer Region ◽  
Olea Europaea L ◽  
Chloroplast Genomes ◽  
Mitochondrial Region ◽  
Olive Trees ◽  
Olea Europaéa

The inheritance of mitochondrial and chloroplast genomes does not follow Mendelian laws, but proceeds by vegetative segregation. Most organisms show organelle homoplasmy, which is probably produced and maintained during sexual reproduction. We have tested the effect of prolonged vegetative multiplication in the maintenance of mitochondrial homoplasmy and the generation of heteroplasmy in cultivated olive trees, Olea europaea L. Seven trees, each representing a different variety of olive, were analysed by the study of an intergenic spacer region of the mitochondrial genome. A very high level of heteroplasmy was detected in all cases. We found multiple genome variants of the sequence analysed. The frequency of genomes with no changes in the spacer region was 11.5%. This means that 88.5% of genomes contain at least one change. The same spacer mitochondrial region was sequenced in several clones from four olive trees of a second generation of sexually reproduced trees. In these trees, many clones were identical and had no changes, which represents a clear reduction of the heteroplasmy (p < 0.001). Therefore, this work supports the relevance of the role of sexual reproduction in the maintenance of mitochondrial homoplasmy and also shows that mutations accumulate in a non-coding sequence of the mitochondrial genome when vegetative propagation is maintained for a long period of time.Key words: mitochondrial genome, homoplasmy, heteroplasmy, olive trees, vegetative reproduction, sexual reproduction.

Reproduction of salal (Gaultheriashallon) under forest canopy

1990 ◽  
Vol 20 (1) ◽  
pp. 91-100 ◽  
Author(s):  
F. L. Bunnell
Keyword(s):  
Sexual Reproduction ◽  
Forest Canopy ◽  
Vegetative Reproduction ◽  
Resource Limitation ◽  
Shoot Density ◽  
Physiological Integration ◽  
Forest Canopies ◽  
Plant Persistence ◽  
Crown Closure ◽  
Optimality Models

Sexual and vegetative reproduction of salal (Gaultheriashallon Pursh) was measured under forest canopies of different closure. Sexual reproduction occurred only at ≤33% closure; vegetative reproduction occurred under sparse and dense closure. Crown closure influenced sexual reproduction primarily through interception of radiation and associated reductions in salal vigour. Irradiance had a greater influence on the mode of reproduction than did shoot density, and allocation of total reproductive effort (sexual plus vegetative) was contrary to optimality models, but consistent with resource limitation. No shoot <5 years old flowered; shared costs of flowering indicated physiological integration among salal shoots. Vegetative reproduction was negatively associated with age (r2 = 0.95), and 85% of the space occupied after 9 years of growth was occupied during the first 3 years. Under canopy the spatial pattern of salal shoots was better adapted to maintain plant persistence than to colonize new areas. Implications of salal's rates and modes of reproduction to forest and wildlife management are noted.

scholarly journals Reproductive strategies and dimorphic seeds germination in Trifolium argentinense Speg., an amphicarpic species

2019 ◽  
Vol 25 (3) ◽  
pp. 66-79
Author(s):  
Ionara Fátima Conterato ◽  
Maria Teresa Schifino-Wittmann ◽  
Diego Bitencourt David ◽  
Jorge Dubal Martins
Keyword(s):  
Sexual Reproduction ◽  
Reproductive Strategies ◽  
Vegetative Reproduction ◽  
Rio Grande ◽  
Soil Surface ◽  
Rio Grande Do Sul ◽  
Storage Roots ◽  
Depth Effect ◽  
Seeds Germination ◽  
Better Than

Native from Rio Grande do Sul natural pastures, Trifolium argentinense Speg. has sexual reproduction through aerial and subterranean seeds (amphicarpy) and vegetative reproduction by regrowth from storage roots. In this study the seeds produced at the soil-surface flowers, the depth effect and scarification on the aerial and subterranean seeds germination and the storage roots produced by plants derived from the two types of seeds were evaluated. The aerial (0.10 cm) and soil-surface (0.11 cm) seeds were similar in size, but smaller than the subterranean seeds (0.14 cm), with no significant variation in the production of the three types of seeds. Aerial and subterranean seeds scarified at and sowed 2.5 cm deep germinated better than the scarified and non-scarified seeds sowed on the soil-surface and at 7.0 cm, evincing a depth effect on seed germination. Although amphicarpic, T. argentinense first invests in the production of the storage roots making sure the cloning of specific genotypes and allowing the plants to persist vegetatively year after year without the need for regeneration by seeds in unfavorable environments for sexual reproduction, such as in Rio Grande do Sul natural pastures, where hard grazing and trampling can destroy the aerial part of the plants.  

Different levels of rainfall and trampling change the reproductive strategy of Kobresia humilis in the Qinghai-Tibet Plateau

2020 ◽  
Vol 42 (2) ◽  
pp. 143
Author(s):  
Zhen Peng ◽  
Hong Xiao ◽  
Xiang He ◽  
Changlin Xu ◽  
Taotao Pan ◽  
...  
Keyword(s):  
Sexual Reproduction ◽  
Reproductive Strategy ◽  
Vegetative Reproduction ◽  
Tibet Plateau ◽  
Single Leaf ◽  
Tibetan Sheep ◽  
Average Rainfall ◽  
Regulation Function ◽  
Qinghai Tibet Plateau ◽  
Different Levels

The sedge Kobresia humilis (C.A. Mey. ex Trautv.) Serg. is the dominant plant in the alpine meadows of China’s Qinghai-Tibet Plateau, which has experienced substantial grassland degradation due to reduced rainfall and overgrazing. In this study we sought to determine the reproductive strategy of K. humilis under three levels of rainfall and seven levels of trampling by Tibetan sheep and yaks with a two year simulation trial on the Plateau. With a reduction in rainfall and an increase in trampling intensity, there was a decrease in sexual reproduction indices, plant height and single leaf number. The highest rainfall promoted sexual reproduction, whereas average rainfall was conducive to vegetative reproduction, and the lowest rainfall inhibited reproduction. The reproductive strategy of K. humilis could be judged according to the average rainfall from July to August. Notably, after two years of low rainfall and a heavy trampling treatment, K. humilis produced more seeds with smaller size. The rainfall presented a two-way regulation function in the trampling effect on K. humilis reproductive characteristics.

GROWTH AND ENERGY CONTENT OF THREE FORAGE GRASSES FROM THE MIDDLE EAST RANGELANDS

2001 ◽  
Vol 49 (2) ◽  
pp. 119-131 ◽  
Author(s):  
A. A. El-Khatib ◽  
A. K. Hegazy
Keyword(s):  
Saudi Arabia ◽  
Sexual Reproduction ◽  
Energy Content ◽  
Wide Spectrum ◽  
Vegetative Reproduction ◽  
Dry Weight ◽  
Perennial Grasses ◽  
Forage Grasses ◽  
Rhizome Growth ◽  
Phenological Phases

This study was conducted on three naturally growing populations of the perennial grasses Panicum turgidum Forssk, Lasiurus scindicus Henrard and Pennisetum divisum Henrard in Egypt, south west Saudi Arabia and Qatar. Vegetative reproduction occurs by rhizome growth and sexual reproduction by tillering, where each tiller may end with a spike. The failure of sexual reproduction is mainly related to the extremely arid conditions and the overgrazing of flowering branches or seeds before dispersal. Phenological behaviour varied among species and differed within the same species in the three study areas. The earliness/lateness and narrow/wide spectrum of the active phenological phases (vegetative growth, flowering and fruiting) were species-dependent rather than locality-dependent. The phenophases of the three species in Saudi Arabia and Qatar proceeded at a faster rate than in Egypt. The plants collected from Saudi Arabia and Egypt attained higher energy content than those collected from Qatar. The overall energy content of P. turgidum (over 6 kcal. g -1 dry weight) is higher than that of L. scindicus and P. divisum (less than 6 kcal. g -1 dry weight). During the peak flowering/fruiting time, the fruits and rhizomes of the three species showed higher energy content than the roots and shoots. When the growth characteristics and energy content were taken as a measure of the grazing value, P. turgidum had better value as a forage plant than the other two species.

The Reproductive Behaviour and the Nature of Sexual Selection in Scatophaga Stercorarial. (Diptera: Scatophagidae)

Behaviour ◽  
1970 ◽  
Vol 37 (1-2) ◽  
pp. 140-168 ◽  
Author(s):  
G.A. Parker
Keyword(s):  
Sexual Selection ◽  
Reproductive Cycle ◽  
Delay Time ◽  
Selective Advantage ◽  
Reproductive Behaviour ◽  
Average Density ◽  
Normal Duration ◽  
Female Behaviour ◽  
Passive Phase ◽  
Do So

AbstractFemales in all stages of their reproductive cycle around dung are equally attractive in eliciting encounters from searching males. On contact, all females which still have eggs to lay are mated (or remated), generally (i.e. over 75%) in their first encounter. All such females copulate for a normal duration, irrespective of previous matings. However, females which have completed oviposition are much less attractive to males on contact and though about 35% of post-oviposition females copulate as a result of their first encounter, only about half of them will have begun genital contact even if allowed six encounters with males. The female behaviour does not appear to be involved in this effect. Matings with post-oviposition females last only 43% of the normal duration. This effect may be due at least in part to the side to side ('swaying') movement performed by the female. It is extremely rare in nature for females to oviposit without a male mounted in attendance (i.e. in the 'passive phase'), though females will do so quite readily if separated artificially. The female initiates separation only after all the egg batch is laid, and after separation she flies immediately upwards and away from the dropping. Female quiescence appears to be necessary for the male to adopt the passive phase; swaying during genital contact and immediately after precedes separation without a passive phase. Females remain quiescent if they still have eggs to lay (even when already mated) and fresh dung is present, though the continuous reception of fresh dung is not necessary. Females sway fairly persistently if they have completed oviposition or there is no dung stimulus. Most females examined on arrival at the dropping (and before being found by a male) already had sperm in their spermathecae, presumably from matings at previous ovipositions since all females mate on arrival at the dung and there are several successive batches of eggs. It is predicted that receptivity before all the eggs are laid may now be of selective advantage to the female. The performance of non-receptivity as exhibited by post-oviposition females involves the female in an average rejection delay of 2.7 min. per encounter. At the average density of searching males present on the dung this rejection delay time would involve the female in much more time waste than full receptivity, since after mating the passive male undertakes the rejection of other males during oviposition. Even allowing for time wasted in recopulation following take-over (i.e. when a second male takes possession of the female), a female with full receptivity would save about 50 min. per oviposition cycle compared to one showing rejection. The passive phase is presumably of advantage to the male in preventing further inseminations, sperm from which could compete with his own for the fertilisation of the female's eggs. After oviposition, the female initiates termination of the passive phase by swaying reactions which cause the male to dismount. She then flies from the dropping.

Social Infertility and the Quest for Parenthood

2017 ◽  
Author(s):  
Judith Daar
Keyword(s):  
Social Structure ◽  
Sexual Reproduction ◽  
Social Relationships ◽  
Reproductive Cycle ◽  
The Other ◽  
Same Sex ◽  
Medical Assistance ◽  
Heterosexual Intercourse ◽  
Same Sex Couples ◽  
Natural Reproduction

This chapter talks about how for many couples, their physical expressions of love will never yield a baby. The largest faction of this cohort consists of the medically infertile—those who lack the physical capacity to accomplish the reproductive cycle of conception, gestation, and childbirth through heterosexual intercourse. The other faction of the “nonproductive lovemaking” cohort includes those with social infertility—the inability to conceive and maintain a pregnancy within a particular social structure without medical assistance. People with social infertility may or may not be medically infertile, but the structure of their intimate social relationships, or lack thereof, make sexual reproduction an impossibility. The socially infertile include single and transgender individuals and same-sex couples who lack access to natural reproduction.

Influence of Chemical Receptivity On Reproductive Behaviour of the Male Three-Spined Stickleback (Gasterosteus Aculeatus L.)

Behaviour ◽  
1983 ◽  
Vol 86 (1-2) ◽  
pp. 100-165 ◽  
Author(s):  
J.P.C. De Bruin ◽  
M.E. VAN DER MECHÉ-JACOBI ◽  
J. Segaar ◽  
A.P. Van Der Meche
Keyword(s):  
Reproductive Cycle ◽  
Sexual Behaviour ◽  
Gasterosteus Aculeatus ◽  
Cranial Nerves ◽  
Reproductive Behaviour ◽  
Exceptional Case ◽  
Nest Building ◽  
Hormonal Changes ◽  
Behavioural Changes ◽  
Reproductive Activities

AbstractThe present investigation is concerned with chemoreceptivity in the male three-spined stickleback (Gasterosteus aculeatus L.) during reproductive behaviour. The functions of cranial nerves were studied with regard to nest building (N), the increase in the zigzag dance (a measure of the sexual tendency (S)) between N and the day of fertilization (F) of the eggs, the zigzag dance between F and the day of hatching (H), suppression of the zigzag dance (if still present) at H, and fanning activity (P) during these days of a reproductive cycle (F-H). The methods of quantifying S and P, as well as the methods of sectioning the olfactory nerves and the branches of cranial nerves possibly involved in the conduction of chemical stimuli are described. The behavioural changes observed after sectioning the olfactory nerves, branches of cranial nerves or combinations of these nerves are compared with behavioural data of unoperated fish. Special attention is given to behavioural changes following regeneration of transected nerves. Nest building is still possible after sectioning of the olfactory nerves, but occurs only in a few fish. The functioning of the olfactory nerves might influence the development of nest building behaviour by inducing hormonal changes, necessary to start such reproductive activities. During the period between N and F (the latter determined by the observer), the number of zigzags (S) increases from zero up to 100 or more per 5 minutes. The olfactory nerves are indispensable for the promotion of sexual behaviour during this period. It seems likely that these nerves are necessary to induce hormonal changes in such a way that the reproductive cycle can proceed from nest building to courtship stage. In the exceptional case that a nest was built by a fish in which the olfactory nerves had been sectioned, the zigzag score remaining low, all other reproductive activities still occurred, including fertilization. Fanning activity in such fish appeared to be quantitatively normal. When the olfactory nerves were sectioned between N and F, at a stage when the zigzag scores had reached an essential level ( 100 per 5 min), both sexual and fanning activity between F and H were normal. This is explained by the supplementary functioning of both the ramus posttrematicus IX and the ramus pretrematicus X1. Both eggs and embryos stimulate sexual behaviour between F and H. The olfactory nerves exert an exciting function with regard to sexual behaviour during the first days of the cycle (F-H). The area in the roof of the pharynx, situated between the first and second gill arches appeared to perceive stimuli from eggs and embryos, exciting sexual behaviour (referred to as sex-excitation area). The sensory fibres from this area run in a dorsal direction, some joining the rami pharyngei X1, others one of the rami pharyngei IX (referred to as the S-anastomosis), their excitation increasing during the course of the cycle. The S-anastomosis which joins the ramus posttrematicus IX near or just dorsal of the second arteria branchialis dorsalis, exites sexual behaviour during most days of the cycle (F-H). Similarly, the rami pharyngei X1 which join the ramus pretrematicus X1 at a point dorsal of the second arteria branchialis dorsalis, excite sexual behaviour during the last days of the cycle. The presence of young following hatching suppresses sexual behaviour, if still present, at H. Such stimuli are perceived by the rami pharyngei IX, which join the ramus posttrematicus IX near or dorsal to the first arteria branchialis dorsalis. Perceiving such stimuli results in an immediate suppression of sexual behaviour. Both eggs and embryos also stimulate fanning behaviour between F and H. Our experiments have shown that the following three nerves are involved in the conduction of such stimuli: nervus olfactorius, ramus posstrematicus IX (including its anastomosis with the ramus pretrematicus X1, referred to as the F-anastomosis), and the ramus pretrematicus X1. The involvement of the cranial nerves I, IX and X in the reproductive activities of the male three-spined stickleback is illustrated in a schematic way in Fig. 27.

The role of sexual reproduction in maintaining populations of Halophila decipiens: implications for the biodiversity and conservation of tropical seagrass ecosystems

1999 ◽  
Vol 5 (4) ◽  
pp. 260 ◽  
Author(s):  
W. Judson Kenworthy
Keyword(s):  
Life History ◽  
Sexual Reproduction ◽  
Clonal Growth ◽  
World Wide ◽  
Vegetative Reproduction ◽  
Indian River Lagoon ◽  
Sexual Life ◽  
Life History Strategies ◽  
Relative Importance ◽  
Seagrass Ecosystems

In subtropical and tropical communities, seagrass species commonly range over an order of magnitude in size and biomass. This biodiversity corresponds with differences in the relative importance of sexual (seed production) and asexual (clonal growth) life history strategies in the maintenance of seagrass populations. Clonal growth and vegetative reproduction are important in maintaining populations of larger-bodied species. As size of species and degree of clonality decrease, the importance of sexual reproduction increases. World-wide, the smallest species in tropical seagrass ecosystems are represented by the most taxonomically diverse, sexually fecund genus, Halophila. A four-year study of the submarine light regime and seasonal growth cycles of Halophila decipiens and other seagrasses in the Indian River Lagoon, Florida, USA provides a comparative context in which to illustrate the relative importance of different life history strategies in tropical seagrass ecosystems world-wide. While sexual reproduction is critical for maintaining some geographically extensive small-bodied seagrass systems in disturbed and extreme environments, there is also evidence to suggest that the quantitative importance of sexual reproduction may be underestimated for larger, highly clonal species like Thalassia testudinum. Future efforts to conserve tropical seagrass ecosystems necessitates a more comprehensive understanding of the evolutionary consequences of sexual reproduction and a more quantitative evaluation of the population dynamics resulting from the sexual life history strategies of different species.

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