self pollination of aroids

From: "zach" r2ot at charter.net> on 2003.05.12 at 19:45:50(10246) hello does anyone here know which genera of tuberous aroids can and can not be self pollinated succesfully? zach

From: Marc Gibernau gibernau at cict.fr> on 2003.05.13 at 08:13:11(10248) Dear Zach, Aroids is a big family with great variability. Due to the protogyny, self-pollination is not supposed to be common (but several taxa have overlapping stigma receptivity and pollen release). Arisarum vulgare can be self-pollinated, if you brush the stigma with a paintbrush. +More For example in Arum, you can not self-pollinated within a same inflorescence but in many cases you can "self"-pollinated between inflorescences of a same individuals (that is called geitonogamy). Do you have some genera in mind? All the best, Marc

From: "Julius Boos" ju-bo at msn.com> on 2003.05.18 at 12:27:50(10266) Dear Zack, Marc and Friends, I have a couple observations and comments on this subject-- in Urospatha the female and then the male anthesis are very obvious (as I noted in my notes on this genus in Aroideana), the female anthesis takes place just as the spathe begins to open, and drops of liquid will be observed on the stigmas. This phase lasts several days, then the tips of the stigmas turn brown and dry up. Soon after the female phase is completed, the strands of pollen can then be observed being produced, starting at the very TOP of the spadix and slowly working downward the entire length, and this phase can take a week to ten days or more. Because these two phases take place pretty far apart and with no apparent 'overlap', and the female stigmas are dry when the pollen is being shed, I do not believe self-pollination can take place. But---on a large mature plant just a very few fruit will still develop and contain some viable seed without apparent pollination , even if there is only one bloom on a single plant in your collection. Small or immature plants will generally abort the bloom with no fruit/seed production, and (as I have suggested previously) perhaps only make their contribution to genitic diversity by their pollen production. I discussed this with the late Dr. Birdsey, he explained that this seed production without pollination is called 'apomixis', and is not self-pollination. Recently I have seen a Xanthosoma acutum Goncalves (section Acontias, a tuberous sp. like most Caladium sps.) develop a full infructesence with only one bloom present, and since this genus also has distinct non-overlapping (as far as we know) female then male anthesis, we suspect apomixis in at least this species in the genus Xanthosoma. I have been pondering the possible 'benefit' of apomixis vs. true self-pollination, and wonder if my thoughts bear merit---we are told that self-pollination is not a 'good' thing because of the non-transference of genetic material between two different plants, so we accept this, and so I wonder how apomixis may 'benefit' a plant. I was thinking----suppose a single seed, transported by a bird or other means, falls on fertile ground and grows into an adult and flowering plant, but too far removed from another plant or population to allow for cross-pollination. The plant blooms, and a few seed are produced by apomixis which fall and grow near to the single parent plant, these plants are clones of the 'mother' plant, but we should bear in mind that in her seed she carries the genes of her parents and the plants that produced 'her'. When a bloom from this population of clones is pollinated by another related clone, there is more mixing of genetic material than would occur if there were true self-pollin ation (but less than if there were cross-pollination by an unrelated plant), so eventually this may allow this population that were originally clones by apomixis to become a self-sustaining and sufficiently diverse in genetic material to be healthy population, as soon there will be sufficient plants in this new population to allow cross pollination to begin. Any comments?? Julius +More Dear Zach, > > Aroids is a big family with great variability. > Due to the protogyny, self-pollination is not supposed to be common (but > several taxa have overlapping stigma receptivity and pollen release). > Arisarum vulgare can be self-pollinated, if you brush the stigma with a > paintbrush. > > For example in Arum, you can not self-pollinated within a same > inflorescence but in many cases you can "self"-pollinated between > inflorescences of a same individuals (that is called geitonogamy). > > Do you have some genera in mind? > > All the best, > > Marc > > >

From: Marc Gibernau gibernau at cict.fr> on 2003.05.19 at 13:49:29(10270) Dear Julius, and Friends, I have many comments on your last message. You are right Julius, there are two phenomena : self-pollination, that is the fertilization of ovules by its own pollen that will consequently lead to the formation of seeds. Apomixis that will lead to the formation of (viable) seeds without any fertilization (e.g. no pollen needed) by ?parthenogenesis/parthenocarpy? of some cells (you have about 10 kinds of apomixis according to the kind of cells implied: egg-cell, endosperm,?). In the first case, two genetic informations are mixed whereas in the second just one genetic information is duplicate. As you mention for Urospatha and Xanthosoma acutum, may not present self-pollination as you observe that protogyny is complete (no overlap). Then apomixis is certainly present in these taxa. The best way to test it (without counting chromosomes) is to castrate (part of) inflorescences to see if just female flowers can produce seeds. In my recent study of Montrichardia (for those interested see attached file), I observe that bagged inflorescences produced seeds, but I was not able to distinguish between self-pollination and apomixis. Such answer needs a specific experiments. +More I suspect that apomixis is common in horticultural aroids as it?s the case for many other families. Fig trees are a good example: about 700 varieties of Ficus carica, the edible fig, created by men. Half of them are parthenocarpic, they produce mature figs with (or not) seeds, but without the fig wasp pollinators (no pollen needed); the other half is more ?traditional? and needs to be pollinated by the fig wasps (carrying pollen) in order to get mature figs. Consequently parthenocarpic fig species can be cultivated in areas outside the natural range of the fig wasp. I don?t know if it?s better to self-pollinated or to reproduce by apomixis, in the first case genetic recombination can occur and can create some variability, but inbreeding can cause low seed set. Some apomictic Rubus species which are self-fertile have developed in a second step self-pollinating mechanisms. Apomixis occurs in many taxa thus it must advantageous in some situations. In many cases, its origin may be from sexually sterile hybrid polyploids (with high genetic diversity). Advantages : Assured reproduction (seeds formation) in absence of pollination (sexual partners) or/and pollinators. Clonal reproduction equivalent of vegetative reproduction ?Cost of meiosis? and the mother genetic contribution 100% (instead of 50%) to her offspring Fix and disseminate an extremely fit genotype. Disadvantages : Accumulate disadvantageous mutations Inability to recombine novel mutants A very narrow niche/habitat No adaptation to stable habitats (often weeds in transitory habitats). You thoughts were right except may be about which system is more advantageous. I don?t know if it helps!!!! Sincerely yours, Marc

From: "Michael Marcotrigiano" mmarcotr at email.smith.edu> on 2003.05.19 at 19:18:48(10272) It is important not to confuse apomixis (embryo produced without pollination - so a clonal seed source) from parthenocarpic - fruit forming without seed = no reproduction) +More _______________________________ Michael Marcotrigiano, Ph.D Director of the Botanic Garden and Professor of Biological Sciences Smith College Lyman Conservatory, 15 College Lane Northampton, MA 01063 email: mmarcotr@smith.edu voice: 413-585-2741; fax: 413-585-2744 www.smith.edu/garden www.science.smith.edu/~mmarcotr ----------------------------------------------------------------------------------- "Art is the unceasing effort to compete with the beauty of flowers and never succeeding." Marc Chagall >>> gibernau@cict.fr 05/19/03 09:49AM >>> Dear Julius, and Friends, I have many comments on your last message. You are right Julius, there are two phenomena : self-pollination, that is the fertilization of ovules by its own pollen that will consequently lead to the formation of seeds. Apomixis that will lead to the formation of (viable) seeds without any fertilization (e.g. no pollen needed) by ?parthenogenesis/parthenocarpy? of some cells (you have about 10 kinds of apomixis according to the kind of cells implied: egg-cell, endosperm,?). In the first case, two genetic informations are mixed whereas in the second just one genetic information is duplicate. As you mention for Urospatha and Xanthosoma acutum, may not present self-pollination as you observe that protogyny is complete (no overlap). Then apomixis is certainly present in these taxa. The best way to test it (without counting chromosomes) is to castrate (part of) inflorescences to see if just female flowers can produce seeds. In my recent study of Montrichardia (for those interested see attached file), I observe that bagged inflorescences produced seeds, but I was not able to distinguish between self-pollination and apomixis. Such answer needs a specific experiments. I suspect that apomixis is common in horticultural aroids as it?s the case for many other families. Fig trees are a good example: about 700 varieties of Ficus carica, the edible fig, created by men. Half of them are parthenocarpic, they produce mature figs with (or not) seeds, but without the fig wasp pollinators (no pollen needed); the other half is more ?traditional? and needs to be pollinated by the fig wasps (carrying pollen) in order to get mature figs. Consequently parthenocarpic fig species can be cultivated in areas outside the natural range of the fig wasp. I don?t know if it?s better to self-pollinated or to reproduce by apomixis, in the first case genetic recombination can occur and can create some variability, but inbreeding can cause low seed set. Some apomictic Rubus species which are self-fertile have developed in a second step self-pollinating mechanisms. Apomixis occurs in many taxa thus it must advantageous in some situations. In many cases, its origin may be from sexually sterile hybrid polyploids (with high genetic diversity). Advantages : Assured reproduction (seeds formation) in absence of pollination (sexual partners) or/and pollinators. Clonal reproduction equivalent of vegetative reproduction ?Cost of meiosis? and the mother genetic contribution 100% (instead of 50%) to her offspring Fix and disseminate an extremely fit genotype. Disadvantages : Accumulate disadvantageous mutations Inability to recombine novel mutants A very narrow niche/habitat No adaptation to stable habitats (often weeds in transitory habitats). You thoughts were right except may be about which system is more advantageous. I don?t know if it helps!!!! Sincerely yours, Marc

From: "Julius Boos" ju-bo at msn.com> on 2003.05.20 at 09:12:39(10274) Thanks for the comment! In the genus Urospatha there seems to be true apomixis, as there are only a very few fruit produced on a spadix that has not been pollinated, and these fruit generally contain less that their full 'quota' of seeds, but there are viable seed produced in most of the few fruit, thereby continuing the reproductive process without cross or self pollination. Julius +More > It is important not to confuse apomixis (embryo produced without > pollination - so a clonal seed source) from parthenocarpic - fruit > forming without seed = no reproduction) > > _______________________________ > > Michael Marcotrigiano, Ph.D > Director of the Botanic Garden and Professor of Biological Sciences > Smith College > Lyman Conservatory, 15 College Lane > Northampton, MA 01063 > email: mmarcotr@smith.edu > voice: 413-585-2741; fax: 413-585-2744 > www.smith.edu/garden > www.science.smith.edu/~mmarcotr > -------------------------------------------------------------------------- --------- > "Art is the unceasing effort to compete with > the beauty of flowers and never succeeding." > Marc Chagall > > >>> gibernau@cict.fr 05/19/03 09:49AM >>> > Dear Julius, and Friends, > > I have many comments on your last message. > > You are right Julius, there are two phenomena : > self-pollination, that is the fertilization of ovules by its own pollen > that will consequently lead to the formation of seeds. > Apomixis that will lead to the formation of (viable) seeds without > any > fertilization (e.g. no pollen needed) by ?parthenogenesis/parthenocarpy? > of > some cells (you have about 10 kinds of apomixis according to the kind of > cells implied: egg-cell, endosperm,?). > > In the first case, two genetic informations are mixed whereas in the > second > just one genetic information is duplicate. > > As you mention for Urospatha and Xanthosoma acutum, may not present > self-pollination as you observe that protogyny is complete (no overlap). > Then apomixis is certainly present in these taxa. The best way to test > it > (without counting chromosomes) is to castrate (part of) inflorescences > to > see if just female flowers can produce seeds. In my recent study of > Montrichardia (for those interested see attached file), I observe that > bagged inflorescences produced seeds, but I was not able to distinguish > between self-pollination and apomixis. Such answer needs a specific > experiments. > > I suspect that apomixis is common in horticultural aroids as it?s the > case > for many other families. Fig trees are a good example: about 700 > varieties > of Ficus carica, the edible fig, created by men. Half of them are > parthenocarpic, they produce mature figs with (or not) seeds, but > without > the fig wasp pollinators (no pollen needed); the other half is more > ?traditional? and needs to be pollinated by the fig wasps (carrying > pollen) > in order to get mature figs. Consequently parthenocarpic fig species can > be > cultivated in areas outside the natural range of the fig wasp. > > I don?t know if it?s better to self-pollinated or to reproduce by > apomixis, > in the first case genetic recombination can occur and can create some > variability, but inbreeding can cause low seed set. Some apomictic Rubus > species which are self-fertile have developed in a second step > self-pollinating mechanisms. > > Apomixis occurs in many taxa thus it must advantageous in some > situations. > In many cases, its origin may be from sexually sterile hybrid polyploids > (with high genetic diversity). > > Advantages : > > Assured reproduction (seeds formation) in absence of pollination (sexual > partners) or/and pollinators. > Clonal reproduction equivalent of vegetative reproduction > ?Cost of meiosis? and the mother genetic contribution 100% (instead of > 50%) > to her offspring > Fix and disseminate an extremely fit genotype. > > Disadvantages : > Accumulate disadvantageous mutations > Inability to recombine novel mutants > A very narrow niche/habitat > No adaptation to stable habitats (often weeds in transitory habitats). > > You thoughts were right except may be about which system is more > advantageous. > I don?t know if it helps!!!! > > Sincerely yours, > > Marc >

From: "Julius Boos" ju-bo at msn.com> on 2003.05.20 at 09:28:30(10275) Dear Marc and Friends, Thank you for your most informative and interesting comments! I think we both agree completely without realizing it! I am not an expert on these matters, but was trying to determine/illustrate that apomixis was at least as good and perhaps better than self-pollination, as perhaps there was more and different genetic material available in apomixis for continued and later cross-pollination in a population of plants that were started by just one good seed originally produced from cross-pollination, but growing all by itself in a remote area. I thought that perhaps reproduction by apomixis (vs. cross-pollination) until there were a few plants in this new population to enable cross-pollination to begin may be 'the better of two evils' as it were, but obviously not as 'good' as cross-pollination in a large and thereby very genetically variable population. Julius +More >>>>>Dear Julius, and Friends, I have many comments on your last message. You are right Julius, there are two phenomena : self-pollination, that is the fertilization of ovules by its own pollen that will consequently lead to the formation of seeds. Apomixis that will lead to the formation of (viable) seeds without any fertilization (e.g. no pollen needed) by "parthenogenesis/parthenocarpy" of some cells (you have about 10 kinds of apomixis according to the kind of cells implied: egg-cell, endosperm,.). In the first case, two genetic informations are mixed whereas in the second just one genetic information is duplicate. As you mention for Urospatha and Xanthosoma acutum, may not present self-pollination as you observe that protogyny is complete (no overlap). Then apomixis is certainly present in these taxa. The best way to test it (without counting chromosomes) is to castrate (part of) inflorescences to see if just female flowers can produce seeds. In my recent study of Montrichardia (for those interested see attached file), I observe that bagged inflorescences produced seeds, but I was not able to distinguish between self-pollination and apomixis. Such answer needs a specific experiments. I suspect that apomixis is common in horticultural aroids as it's the case for many other families. Fig trees are a good example: about 700 varieties of Ficus carica, the edible fig, created by men. Half of them are parthenocarpic, they produce mature figs with (or not) seeds, but without the fig wasp pollinators (no pollen needed); the other half is more "traditional" and needs to be pollinated by the fig wasps (carrying pollen) in order to get mature figs. Consequently parthenocarpic fig species can be cultivated in areas outside the natural range of the fig wasp. I don't know if it's better to self-pollinated or to reproduce by apomixis, in the first case genetic recombination can occur and can create some variability, but inbreeding can cause low seed set. Some apomictic Rubus species which are self-fertile have developed in a second step self-pollinating mechanisms. Apomixis occurs in many taxa thus it must advantageous in some situations. In many cases, its origin may be from sexually sterile hybrid polyploids (with high genetic diversity). Advantages : Assured reproduction (seeds formation) in absence of pollination (sexual partners) or/and pollinators. Clonal reproduction equivalent of vegetative reproduction 'Cost of meiosis' and the mother genetic contribution 100% (instead of 50%) to her offspring Fix and disseminate an extremely fit genotype. Disadvantages : Accumulate disadvantageous mutations Inability to recombine novel mutants A very narrow niche/habitat No adaptation to stable habitats (often weeds in transitory habitats). You thoughts were right except may be about which system is more advantageous. I don't know if it helps!!!! Sincerely yours, Marc

From: MossyTrail at cs.com on 2003.05.21 at 03:40:40(10276) "Julius Boos" wrote: > >Dear Marc and Friends, > >perhaps there was more >and different genetic material available in apomixis for continued and later >cross-pollination in a population of plants that were started by just one >good seed originally produced from cross-pollination, but growing all by >itself in a remote area. ? ?I thought that perhaps reproduction by apomixis >(vs. cross-pollination) until there were a few plants in this new population >to enable cross-pollination to begin may be 'the better of two evils' as it >were, but obviously not as 'good' as cross-pollination in a large and >thereby very genetically variable population. I presume you are referring to heterozygousness (heterozygosity?); that is, your one single plant has two forms of an allele. Then, when it self-pollinates, the alleles may be recombined to produce previously-hidden diversity. Sorry, I am having trouble expressing myself clearly tonite. Jason Hernandez +More Naturalist-at-Large

From: Marc Gibernau gibernau at cict.fr> on 2003.05.21 at 07:38:53(10277) Dear Julius, Jason & Friends, Apomixis do not produce more and different genetic material as all the seeds are identitical as their mother, they are all clone but instead of being bulbils,... they are seeds. So if the mother was genetically variable (heterozygosite) its offspring will also be... This way of reproduction is like a clonal reproduction that leads to the formation of seeds (with the advantage/disadvantage of been dispersed: new habitat colonization suitable or not!!!). Apomixis in general does not prevent from been cross-pollinated, as Julius mentioned this "breeding system" can operate when sexual partners are lacking later if the population grows apomixis can co-exist or be replaced by cross-pollination. +More Jason is right when he says that self-pollination can create new genetic information by recombination whereas apomixis no (except mutations). The problem with self-pollination is that inbreeding depression can occur: lethal combinations and part of the offspring will die (but it's a form a selection!!!). I hope I have clarified some of the questions. All the best, Marc

From: Marc Gibernau gibernau at cict.fr> on 2003.05.21 at 11:49:54(10278) Dear Julius & Friends, I listed the advantages and disadvantages of apomixis in a previous e-mail. So it will depend on the populational state of your species. If I understand well your question, apomixis will never "mix" genes (it's a cloning multiplication better than reproduction). But apomixis will "keep" all the genes in place (for future mixing if cross-pollination occurs). Self-pollination will mix the genes and all lethal genetic combinations will be +More eliminate (through the death of the individuals bearing them). Thus alleles will be lost (but they were not fit), this is called 'allelic purge'. On the other hand has recombination occurs between alleles, new genetic combinations are created. Here the balance between elimination and creation is (I think) very variable, in some case it's negtive oin other positive. I think that at the beginning genetic combinations will be lost and that genetic creation will come in a second time. But here again it will depend on genetic structure and breeding system of your taxa. Apomixis do not create but conserve a given genetic state whereas self-pollination eliminate but also create genetic combinations. I don't know what is "better". What happens is that such mechanisms (can) exist and can be selected or counter-selected according to the population situation. It's clearer? Sincerely yours, Marc

From: Marc Gibernau gibernau at cict.fr> on 2003.05.26 at 08:14:50(10289) Dear Julius, No problem, It has been a pleasure to discuss with you and others. I agree with your last message about population founding and apomixis advantages in this case. Of course it would be very interesting to look closely at these phenomena in Urospatha and Lasioids. May be one day.... All the best, Marc

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