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Sex change in plants: Old and new observations and new hypotheses

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Abstract

Evidence is presented that individuals of a large number of dioecious and subdioecious plant species are able to alter their sexual state in response to changes in the ambient environment and/or changes in size or age. We suggest that lability of sexual expression probably has survival value where a significant portion of the females must otherwise bear the cost of fruit production in unfavorable environments. We demonstrate that in patchy environments of the proper scale and variability in quality, labile sexual expression will enhance an individual's genetic contribution to the next generation.
... The change in proportion of sex type with fluctuating environment could indicate an adaptive response to provide reproductive advantage (Freeman et al. 1997;Vaughton and Ramsey 1998). Previous research demonstrated that factors such as resource availability, climate, and genetic predispositions can influence variations in sex ratios (Sakai and Weller 1999). ...
... Hermaphrodite flowers provide flexibility by allowing plants to reproduce both by self and cross pollination, potentially offering an advantage in diverse or unpredictable environments (Charnov 1982;Vaughton and Ramsey 1998). The prevalence of different floral types can significantly be influenced by the environmental factors (Freeman et al. 1997). Our results show a higher maximum percentage of hermaphrodite flowers for Rajouri, which may indicate favourable conditions for self-pollination or a strategy to enhance reproductive success under fluctuating environmental conditions. ...
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Wild pomegranate (Punica granatum L.), an important fruit in tropical and subtropical regions like Central Asia and Northern India, is highly valued for its economic and medicinal benefits. However, despite its potential, natural production of the fruit is hindered by pest damage and variation in fruit yield due to environmental factors. Genetic improvement and a deeper understanding of the phenology and reproductive behavior are essential for enhancing its yield, creating superior genotypes, and ensuring sustainable cultivation and conservation. Thus, the study was conducted in Udhampur and Rajouri districts of Jammu and Kashmir focusing on the floral biology and phenology of wild pomegranate. Field investigations covered sex ratios, flowering events, pollen viability, and breeding system. The study reveals that Udhampur has a slightly higher proportion of andromonoecious plants compared to Rajouri. Hermaphrodite flowers in Rajouri demonstrate superior reproductive traits, including higher anther counts, pollen production, and fruit set. Floral biology reveals a clear phenological sequence, with anther dehiscence occurring 120 h post-anthesis, followed by stigma receptivity after 24 h, promoting cross-pollination. The calculated fruit set rate is 72.7% in Rajouri and 65.7% in Udhampur districts exceed their respective reproductive efficiencies. In vitro pollen germination analysis revealed that male pollen consistently outperformed hermaphrodite pollen at all tested temperatures, particularly at 4 °C, while both types experienced decreased germination rates at higher temperatures. Pollination experiments show significantly higher fruit set in cross-pollination methods, particularly xenogamy. Wind pollination shows a clear decline in pollen deposition rates with increasing distance from the source, indicating that proximity greatly influences pollen distribution and emphasizing the importance of pollinators. Collectively, these findings contribute to a deeper understanding of plant reproductive ecology and have implications for the conservation and management of this species in varying climatic conditions.
... Cannabis sativa L. (Cannabaceae) is sexually labile, possessing the ability to flexibly transition from female or male reproductive function to a cosexual phenotype that produces both ovules and pollen grains [1][2][3][4][5]. Cosexual plants are naturally occurring in C. sativa, often seen in response to stressful external environments [3][4][5], but they can also be synthetically induced through application of chemical treatment [6][7][8][9][10]. ...
... Cannabis sativa L. (Cannabaceae) is sexually labile, possessing the ability to flexibly transition from female or male reproductive function to a cosexual phenotype that produces both ovules and pollen grains [1][2][3][4][5]. Cosexual plants are naturally occurring in C. sativa, often seen in response to stressful external environments [3][4][5], but they can also be synthetically induced through application of chemical treatment [6][7][8][9][10]. Manipulation of C. sativa's sexual expression (a process known as sexual lability) has given rise to the production of feminized seeds. ...
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Cannabis sativa L. is cultivated globally for its cannabinoid-dense inflorescences. Commercial preference for sinsemilla has led to the development of methods for producing feminized seeds through cross-pollination of cosexual (masculinized) female plants. Although the induction of cosexuality in Cannabis plants is common, to date, no work has empirically tested how masculinization of female Cannabis plants impacts male flowering, pollen production, pollen fitness, and related life-history trade-offs. Here, we cultivated a population of Cannabis plants (CFX-2) and explored how the route to cosexuality (drought vs. chemical induction) impacted flowering phenology, pollen production, and pollen fitness, relative to unsexual male plants. Unisexual males flowered earlier and longer than cosexual plants and produced 223% more total pollen (F2,28 = 74.41, p < 0.001), but per-flower pollen production did not differ across reproductive phenotypes (F2,21 = 0.887, p = 0.427). Pollen viability was 200% higher in unisexual males and drought-induced cosexuals (F2,36 = 189.70, p < 0.001). Pollen non-abortion rates only differed in a marginally significant way across reproductive phenotypes (F2,36 = 3.00, p = 0.06). Here, we demonstrate that masculinization of female plants impacts whole-plant pollen production and pollen fitness in Cannabis sativa.
... Gender expression is vital in determining the genetic contribution of plants as either male or female [1]. Various factors, such as size, growth rate, mortality, light, and nutrient resources, can impact the ontogenic sex change in plant species [7,8,9,10,11,12]. Resourcedependent gender plasticity is typically observed in natural plant populations, which ultimately helps to maintain gender dimorphism [13]. ...
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Conifers are reported to exhibit predominantly monoecious behaviour however, numerous species and some genera show uncertainties regarding their gender expression. The factors influencing the sexual differentiation of strobili in monoecious or dioecious conifers remain poorly understood. To investigate this unpredictable phenomenon in conifers, we selected three populations representing pure stands of Cedrusdeodara in dense temperate forests of Northern India, specifically one in Uttarakhand and two in Himachal Pradesh. Each site was surveyed, and total 900 trees were marked as male, female, monoecious and neutral trees based on their reproductive behaviour and sexual representation. Selection criteria were based on the reproductive age of Cedrusdeodara, as it attains maturity when it reaches a height of 19 to 20 meters. Our findings revealed that Cedrusdeodara exhibits subdioecious behaviour, characterized by the occurrence of four basic sex forms such as male trees, female trees, monoecious trees, and neutral trees. Yearly observations from 2014 to 2016 unveiled that Cedrusdeodara does not exhibit consistent reproductive behaviour. Instead, the species displays a fascinating pattern of alternation between dioecy and monoecy. Additionally, it was also found that individual trees demonstrated change in their expression of sex during each reproductive cycle. These findings underscore the complexity of sex determination and reproductive plasticity in Cedrusdeodara. The study has revealed that the monoecious behaviour was more dominant than the dioecious behaviour, and the individual tree changes its sexual representation depending upon the rate of seed production the previous year. This research pave the way for future investigations into the factors influencing sex expression and reproductive behaviour in conifers and will contribute to our broader knowledge of plant sexuality and plant evolution.
... In the case of our data for P. alpina, the tradeoff lines traced over the fitness landscape ( Figure 4) reveal variation in the shape of the fitness curves ( Figure 5) that suggest that small individuals should allocate most of their reproductive resources to their male function, while larger individuals with more resources should allocate substantially to both male and female functions. With growth, individuals should thus shift from an all-male to a hermaphroditic allocation strategy, i.e., they should display a type of 'sexual diphasy' (46)(47)(48), as indeed observed in wild populations of P. alpina and many other perennial plants (49)(50)(51) and animals (52). ...
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Sex allocation theory successfully predicts sex-ratio variation among organisms with separate sexes, but it has been much less successful in explaining variation in sex allocation in hermaphrodites because the assumption of a direct tradeoff between male and female functions is often violated. Here, we show that sex-allocation theory can be applied to hermaphrodites simply by mapping components of seasonal reproductive success onto a fitness landscape defined by potentially independent measures of allocation to male and female functions on orthogonal axes. Taking this approach allowed us to interpret the complex variation in the reproductive strategy of a long-lived perennial herb ( Pulsatilla alpina ) that produces both male and bisexual flowers and that shifts between male and female allocation among seasons. We find that components of reproductive success for P. alpina map onto a rugged landscape with peaks that reflect an interactive effect of male and female allocations on self-fertilization and total reproductive success and that correspond to the observed sex-allocation strategies adopted by the species in nature. This simple approach should be widely applicable to problems in the study of hermaphroditic reproduction in other plants and animals. Significance Statement Sex allocation theory has helped to explain sex-ratio variation in numerous dioecious species, but it has been difficult to apply to hermaphrodites, in which male-female tradeoffs are often obscure. Here, we show that by mapping fitness estimates for plants with complex allocation patterns on a two-dimensional landscape defined by both male and female allocations, we sidestep the tradeoff assumption. Our analysis reveals fitness peaks that correspond precisely to the strategic allocation decisions adopted by the species in nature. Our simple but novel approach provides a rescue-line for a powerful body of theory that has been criticized for being too difficult to apply to the messy world of hermaphrodites, both in plants and animals.
... Gender expression is vital in determining the genetic contribution of plants as either male or female (Lloyd., 1979). Various factors, such as size, growth rate, mortality, light, and nutrient resources, can impact the ontogenic sex change in plant species (Heslop-Harrison., 1957;Charnov and Bull., 1977;Freeman., 1980;Schlessman., 1986;Korpelainen., 1998;De Jong and Klinkhamer., 2005). Resource-dependent gender plasticity is typically observed in natural plant populations, which ultimately helps to maintain gender dimorphism (Delph and Wolf., 2005). ...
Preprint
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Conifers are reported to exhibit predominantly monoecious behaviour however, numerous species and some genera show uncertainties regarding their gender expression. The factors influencing the sexual differentiation of strobili in monoecious or dioecious conifers remain poorly understood.To investigate this unpredictable phenomenon in conifers, we selected three populations representing pure stands of Cedrus deodara in dense temperate forests of Northern India, specifically one in Uttarakhand and two in Himachal Pradesh. Each site was surveyed, and total 900 trees were marked as male, female, monoecious and neutral trees based on their reproductive behaviour and sexual representation. Selection criteria were based on the reproductive age of Cedrus deodara, as it attains maturity when it reaches a height of 19 to 20 meters.Our findings revealed that Cedrus deodara exhibits subdioecious behaviour, characterized by the occurrence of four basic sex forms such as male trees, female trees, monoecious trees, and neutral trees. Yearly observations from 2014 to 2016 unveiled that Cedrus deodara does not exhibit consistent reproductive behaviour. Instead, the species displays a fascinating pattern of alternation between dioecy and monoecy. Additionally it was also found that individual trees demonstrated change in their expression of sex during each reproductive cycle. These findings underscore the complexity of sex determination and reproductive plasticity in Cedrus deodara. This research pave the way for future investigations into the factors influencing sex expression and reproductive behaviour in conifers and will contribute to our broader knowledge of plant sexuality and plant evolution.
... This change has led to the hypothesis that the nutritional and energetic costs of producing female inflorescences and fruits may be too high for small-sized, younger palms. Consistent with this notion, access to favorable conditions for growth appears to promote femaleness (Freeman et al., 1980;Yamashita et al., 2000;Yamashita and Abe, 2002). ...
Article
Premise The Asian palm Trachycarpus fortunei (Arecaceae: Coryphoideae) is an ornamental species that is widely planted in temperate regions. In Europe, it has spread outside of gardens, particularly on the southern side of the Alps. Sexual expression in the species is complex, varying from dioecy to polygamy. This study investigated (1) sexual floral development and (2) genetic markers implicated in sex determinism. Methods The morphology and anatomy of floral organs at different developmental stages were studied using SEM observations and anatomical sections. Sex determinism was explored using a Genome‐Wide Association Study (GWAS) approach, searching for correlations between 31’000 SNP markers and sex affiliation of 122 palms from 21 wild populations. Key results We observed that sexual differentiation appears late in floral development of T. fortunei. Morpho‐anatomical characters of flowers conducive to panmixia were observed, such as well‐differentiated septal nectaries that are thought to promote cross‐pollination. At the molecular level, homozygous and heterozygous allelic systems with closely linked regions were found for sex determinism in individuals with female and ‘dominant‐male’ phenotypes, respectively. Through our wide sampling in the southern Alps, the closely linked genetic regions in males suggest that at least fifteen percent of wild palms are the direct offspring of ‘males’ that can also produce fertile pistillate flowers. Conclusions Trachycarpus fortunei is a further example of unstable sexual expression found in the family Arecaceae and represents an evolutionary path towards an XY genetic system. Our structural and genetic results may explain the high species dispersal ability in the southern Alps. This article is protected by copyright. All rights reserved.
... In addition to genetic control, sex expression in melon can be modified by external factors, such as mineral nutrition, temperature, water restriction, light intensity, photoperiod, mechanical trauma, and application of growth regulators (Freeman et al., 1980;Girek et al., 2013). There are various studies on the involvement of growth regulators and phytohormones in melon sex determination from the past several decades (Noguera et al., 2005;Papadopoulou et al., 2005;Yamasaki et al., 2005;Little et al., 2007;Boualem et al., 2008;Girek et al., 2013). ...
... Although once believed that plants do not change the types of flowers [2] during their lives, it is now well documented that age, dry soil, high light intensity, etc., could cause a gender difference [3,4] . It's been suggested that exogenous phytohormone, or plant growth regulator (PGR) applications might have an influence on flower gender [5,6] and help regulate sexual expression in flowers. ...
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The effect of foliar treatment with brassinosteroid (BR) on gender distribution in flowers of walnut (Juglans regia L. cv. Chandler) was investigated. Grafted walnut saplings ('Chandler') on the wild walnut (Juglans regia L.) rootstock were planted into 70-liter pots with a soil: peat: perlite medium and grown in pots between 2016-2020. BRs (24-epibrassinolide; EBR and 22(S), 23(S)-homobrassinolide; HBR) were applied at a concentration of 1 mg L-1 for four consecutive years at the time of flower differentiation. The experimental design was completely randomized with three replicates. The results show that BR applications could alter the sexual distribution of the walnut's flower. BRs application significantly increased the number of total flowers and female flowers per tree. The number of female flowers was also increased by the season. The highest number of female flowers (20.9) was observed in the trees in 2020 and the application of 1 mg L-1 of HBR. It was determined that the annual growth of the plant and the increase in the number of females and total flowers were positively related. The effect of BRs indicated that the response was BR-type specific.
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A sex change phenomenon was reported in some free-living, non-sessile coral species of the Family Fungiidae. However, there are no reports describing sex change in sessile colonial species. Timing and cellular processes of sex change are also unclear in corals. Here, we report sex change of the colonial coral, Fimbriaphyllia ancora, and its cellular process. Of 26 colonies monitored at Nanwan Bay, southern Taiwan, about 70% changed their sex every year after annual spawning for least 3-4 consecutive years, i.e., colonies that were male two years ago became female last year, and male again this year. The remaining 30% were permanently male or female. Sex-change and non-sex-change colonies grew in close proximity or even side-by-side. No significant differences were found in colony size between sex-change and non-sex-change colonies. Histological analysis showed that, in female-to-male sex change, small oocytes were present up to 3 months in some gonads after spawning and disappeared by 5 months. This suggests that sex change occurred 4-5 months after spawning. In contrast, in male-to-female sex change, oocytes appeared weeks after sperm release and in most gonads by 3 months, suggesting that male-to-female sex change occurred 0–3 months after sperm release.
Article
Background and Aims Not all plant-pollinator interactions are mutualistic, and in fact, deceptive pollination systems are widespread in nature. The genus Arisaema has a pollination system known as lethal deceptive pollination, in which plants not only attract pollinating insects without providing any rewards, but also trap them until they die. Many Arisaema species are endangered from various disturbances including reduction in forest habitat, modification of the forest understory owing to increasing deer abundance, and plant theft for horticultural cultivation. We aimed to theoretically investigate how lethal deceptive pollination can be maintained from a demographic perspective and how plant and pollinator populations respond to different types of disturbance. Methods We developed and analysed a mathematical model to describe the population dynamics of a deceptive plant species and its victim pollinator. Calibrating the model based on empirical data, we assessed the conditions under which plants and pollinators could coexist, while manipulating relevant key parameters. Key Results The model exhibited qualitatively distinct behaviours depending on certain parameters. The plant becomes extinct when it has a low capability for vegetative reproduction and slow transition from male to female, and plant–insect co-extinction occurs especially when the plant is highly attractive to male insects. Increasing deer abundance has both positive and negative effects because of removal of other competitive plants and diminishing pollinators, respectively. Theft for horticultural cultivation can readily threaten plants whether male or female plants are frequently collected. The impact of forest habitat reduction may be limited compared to that of other disturbance types. Conclusions Our results have emphasised that the demographic vulnerability of lethal deceptive pollination systems would differ qualitatively from that of general mutualistic pollination systems. It is therefore important to consider the demographics of both victim pollinators and deceptive plants to estimate how endangered Arisaema populations respond to various disturbances.
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A population of 1945 seedlings of Ilex opaca Ait. was observed for a period of seven years after field planting. Sex determinations were obtained for 1930 of the seedlings. In general, the staminate plants flowered at an earlier age than did the pistillate plants. However, staminate and pistillate plants were found to occur with equal frequency (1.03/1.00).
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The interaction of the genetic and hormonal regulation of growth, flowering, and sex expression in plants is discussed. The genetic control of these processes is characterized, and data on their hormonal regulation are supplied. The interaction of genetic and hormonal regulation is considered with reference to tall-growing and genetic dwarf forms of the pea and wheat plants. It is shown that in the dwarf forms of the pea plant and in many other varieties, growth stimulation in response to treatment with the phytohormone gibberellic acid is clearly manifested and the expression of genetic dwarfism is eliminated, whereas in dwarf wheats it is expressed only slightly, if at all. At the same time both tall-growing and dwarf forms of both pea and wheat show a clearly defined growth retardation response to treatment with the growth inhibitor, abscisic acid, which causes the expression of physiological dwarfism. The short- and long-day characteristics of the photoperiodic response of plants are described as genetically controlled features, and data are given on the induction of flowering of a long-day variety coneflower grown under short-day conditions with the aid of gibberellins extracted from leaves of long-day vegetative plants of short-day Mammoth tobacco. Data are also supplied on the induction of flowering of a short-day variety, red-leaved goosefoot, grown under continuous light with the aid of metabolites extracted from leaves of the same Mammoth tobacco plants flowering under short-day conditions. This demonstrates the possibility of hormonal regulation of the genetically controlled long-day and short-day characteristics in photoperiodically sensitive plants. Genetic and hormonal regulation of sex expression in two dioecious plants, hemp and spinach, is discussed. It is shown that sex expression in these plants is regulated by gibberellins which are synthesized in leaves and cause male sex expression and by cytokinins which are synthesized in the roots and cause female sex expression. These data indicate that sex expression in dioecious plants is the result of interaction between the genetic apparatus and phytohormones.
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Certain embryological and biochemical effects of the cytokinin (SD 8339) in converting flower sex from male to hermaphrodite were studied in a clone of Vitis vinifera L. (sylvestris). The cytokinin accelerated the meiotic division of the megaspore mother cell, mitotic divisions of the megaspore and cells of pistillate tissue, and increased the rate of protein synthesis in flower buds. Two working hypotheses for the possible mode of action of the cytokinin in sex conversion are presented.
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1. The Science of Genetics. 2. Cellular Reproduction and Model Genetic Organisms. 3. Mendelism: The Basic Principles of Inheritance. 4. Extensions of Mendelism. 5. The Chromosomal Basis of Mendelism. 6. Variation in Chromosome Number and Structure. 7. Linkage, Crossing Over, and Chromosome Mapping in Eukaryotes. 8. The Genetics of Microorganisms. 9. DNA and the Molecular Structure of Chromosomes. 10. Replication of DNA and Chromosomes. 11. Transcription and RNA Processing. 12. Translation and the Genetic Code. 13. Mutation, DNA Repair, and Recombination. 14. Definitions of the Gene. 15. The Techniques of Molecular Genetics. 16. Genomics. 17. Applications of Molecular Genetics. 18. Transposable Genetic Elements. 19. The Genetics of Mitochondria and Chloroplasts. 20. Regulation of Gene Expression in Prokaryotes and Their Viruses. 21. Regulation of Gene Expression in Eukaryotes. 22. The Genetic Control of Animal Development. 23. The Genetic Control of the Vertebrate Immune System. 24. The Genetic Basis of Cancer. 25. Inheritance of Complex Traits. 26. Population Genetics. 27. Evolutionary Genetics. Epilogue: Genetics Yesterday, Today, and Tomorrow, a Personal View. Bibliography. Photo and Illustrations Credits. Glossary. Answers to Odd-Numbered Questions and Problems. Index.