Plants

[spottedlizard20]

Do all plant species have a male and a female form? I know with some varieties of plants you have to have a male and a female form close by so that they can cross polinate and produce seeds, but not all plants produce flowers do they? Is this like a haploid thing or someting where some types of plants can produce seeds on their own without polination and others require polination to produce seeds?

I was also wondering, for the varieties of plants that do produce male and female forms, what determines this? Do they have a type of X and Y chromosome like humans or is this something that is influenced by the environment (like in turtles, you can incubate their eggs above or below a certain temperature and produce different sexes because of the temperature at which the egg was incubated).

Someone was saying that the crimson king cultivar variety of maple trees, when they produce progeny from their seeds, there is only about a 25% chance that the progeny will remain a crimson king and not revert back to the original cultivar variety. Is this some type of recessive genetics?? Could we not simply fertilize one crimson king maple with pollen from another crimson king and produce all crimson kings?? We can do that with recessive animal phenotypic characteristics if we want the progeny to all exhibit a given recessive allele... I realize it is possible that a parent crimson king was mated with a different cultivar variety as they are very closely related types of plants, I thought maybe this would somehow influence the progeny reverting back to the original variety and the probability of producing a crimson king from one of these seeds.

Any input you may have would be GREATLY appreciated Thanks a lot!!

[Glider]

Not all plants are male or female. Some share features of both and can self-pollinate. Others do no require pollination at all, and don't repoduce by seed.

 

I don't know about all plants, but I know a little about trees (I've been growing and studying bonsai for ~20 years). The thing with acer cultivars, is that so many of them originated as sports (point mutations resulting in a different form of growth on a single limb). These cannot be reproduced through seed, and are propogated through successive cuttings, which are usually grafted onto Acer Palmatum (AP) rootstock. Examples are AP 'Deshojo', AP 'Kiyohime', AP 'Katsura' and so-on. None of these do particularly well grown on their own roots (except for a new variant of the Deshojo, which is becoming very popular in Bonsai circles).

 

However, not all cultivars are sports, many are hybrids. These will be crosses of different varieties designed to produce desirable features inherent in each parent (e.g. frost-hardiness in one, leaf shape/size in the other). However, the offspring of these crosses (F1 Hybrids) are often sterile, and those that are not, will hardly ever reproduce true to type, rather they will revert to one or other of the parent types. In any event, the only reliable way to propogate F1 hybrid trees, is (again) to take successive cuttings (and cuttings from the rooted cuttings, and so-on), producing hundreds of genetically identical trees.

[dagaz]

Quote:"Do all plant species have a male and a female form?"

 

No. In fact many, if not most, naturally occuring flowering plants are bisexual - that is they have male and female parts in the same flower on the same tree. Some of these plant species have special receptors in their stigma (the female receptive part) which won't allow pollen from the same flower or even the same individual to prevent it from self-pollinating. Other plant species time it so that even though they have male parts (filament and anther, collectively called stamen) in the same flower as the female parts (ovary, style and stigma, collectively called carpel) they produce and are receptive to pollen at different times. Other plants find self-pollination acceptable and don't have any barriers towards it. And yes there are plants out there which are dioecious (male and female flowers on different plants) or even monoecious (separate male and female flowers on the same tree).

 

Quote:"for the varieties of plants that do produce male and female forms, what determines this?"

 

This is largely genetic.

 

Quote:"but not all plants produce flowers do they?"

 

No, only flowering plants (Angiosperms) produce flowers. Conifers (Gymnosperms) reproduce by cones and ferns (Pteridiophytes) and other primitive plants reproduce by spores. For the ferns and other primitive plants reproduction is asexual.

[Seadragons]

Some flowers do self-pollinate so other things do not have to carry the spores over to a female flower.

[Moontanman]

Do they have a type of X and Y chromosome like humans

 

No, this form of sexual genetics is largely limited to mammals, other animals and plants have other widely varied ways to determine sex. Even in mammals it can be less than accurate and X Y chromosomes can be indeterminate for sexual identity.