rhododendron questions

Discussion in 'Plants: Science and Cultivation' started by Douglas Justice, Jun 18, 2003.

  1. Douglas Justice

    Douglas Justice Active Member UBC Botanical Garden Forums Administrator Forums Moderator VCBF Cherry Scout Maple Society 10 Years

    Messages:
    993
    Likes Received:
    42
    Location:
    Vancouver, Canada
    The following was received via email:

    Rhododendron species have both male and female parts on the same plant and are self-fertile making them hermaphrodites. Correct?

    Some plants only reproduce vegetatively. Is this called eukaryotic and could you give me an example or two of these type of plants.

    Do hermaphrodites and eukaryotes belong to the same plant order; this is crucial.

    And this is why:

    Greer, Galle and others continue to list R.'Balsaminiflora' (several different spellings occur) as a form of R.indicum.

    To me, a sterile Rhododendron is not a species as it cannot participate in the normal reproductive cycle, normal as it applies to rhodies.

    'Balsaminiflora' might be a hybrid of garden origin, I doubt anyone knows for sure.

    So, should a sterile plant be listed as a species rhody?

    I would greatly appreciate your thoughts on this, I have started a thread on the Yahoo Rhodo Group by inviting definitions of 'species' in which Harold Greer deferred the answer to the Coxes.
     
  2. Douglas Justice

    Douglas Justice Active Member UBC Botanical Garden Forums Administrator Forums Moderator VCBF Cherry Scout Maple Society 10 Years

    Messages:
    993
    Likes Received:
    42
    Location:
    Vancouver, Canada
    Functionally bisexual flowers make the plant a hermaphrodite. Separate male (staminate) and female (pistilate or carpellate) flowers on the same plant make the plant monoecious, and separate male and female plants (again, unisexual flowers) are dioecious.

    A eukaryote is a completely different thing -- that term refers to organisms characterized by cells that have a nucleus. You and I and all rhododendrons are eukaryotes. The corresponding alternative is the prokaryote. The prokaryotictic cell is exemplified by primitive, single celled organisms, such as bacteria, whose cells lack a nucleus.

    A species is usually defined as a normally sexually reproducing population. If a plant is sterile, it may be a hybrid (but most rhododendron hybrids are fertile) or just a mutated flower form of a species (e.g., it might be missing some crucial bit of the normal anatomy). For example, double flowered forms of plants are common, the extra petals often derived from mutated staminal tissue (if all of the stamens are replaced, such a double flowered plant is "male-sterile"). It is not uncommon for sterile plants to occur in nature, but most don't last for long, unless they successfully reproduce vegetatively.

    Rhododendron 'Balsaminiflora' (syn: R. balsaminaeflorum) may indeed be a double-flowered selection of R. indicum, but it's equally likely that it's a hybrid or attributable to another species. It does not appear that anyone has proven it conclusively either way.

    Personally, I would not generally call a named cultivar a "species," but the distinction understood by most rhododendron enthusiasts is simply whether a plant is a naturally-occurring entity or a (manufactured) hybrid. So, if the double-flowered plant occurred in the wild, would it be a "species"? Technically, yes, but it would have to have human intervention to maintain it as a garden plant (and normally, it would be given a cultivar name). Hybrids can also occur naturally, and it appears that many species originated as hybrids. Under what category does one place a natural hybrid? The issue is probably better debated around the question: is human intervention necessary to maintain it (i.e., does it have a cultivar name) or does it reproduce true to form in nature?
     

Share This Page