Selection of inheritable traits

Discussion in 'Plants: Science and Cultivation' started by jamkh, Nov 14, 2006.

  1. jamkh

    jamkh Active Member

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    Every reply to my query on the in heritability of acquired traits stated that these are not inheritable, because they are phenotypic expressions and not subject to genetic coding. They say that the dominant traits of a specie is acquired by natural selection, which normally takes many generations to take effect. This point of course is a scientific fact.
    Now going back to the acclimatization process in the specie Wrightia Religiosa which cannot come under the umbrella of Darwin's natural selection. That specie is not native to any tropical region and is a deciduous, temperate plant. The specie could not have been introduced to the tropics for more than 100 years. Thus the time is too short for any natural selection to have any effect. Yet this plant today is a prolific grower in the tropics, requires no dormancy and is now evergreen. It can be concluded that it has adapted, very well, to life in the tropics.
    How then is this possible if external phenotypic modifications do not encode into the genes within the seed?
    Here is what I suspect could have happened.
    Every gene consists of many closely related alleles, one or two becoming dominant while the rest remain dormant/regressive. In the case of the gene concerned with plant hardiness, it contains a series of alleles arranged in a range of hardiness from very hardy to non-hardy. When the plant is hardy the alleles in the hardy end must be the dominant ones and the converse is true too. When the Wrightia adapts to the tropical heat, it does not require to change any genetic code, all it requires is the shift in the selection of alleles towards the non-hardy end. Thus the adaption results in a change in the selection process.
    This of course is a theory but appears logical at the same time. Has anyone got his own theory as well?
     
  2. Daniel Mosquin

    Daniel Mosquin Paragon of Plants UBC Botanical Garden Forums Administrator Forums Moderator 10 Years

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    Hmm... Flora of China reports it is native to S Guangdong in China (a temperate climate) and the tropical Cambodia, Laos, Malaysia, Thailand, and Vietnam...
     
  3. Daniel Mosquin

    Daniel Mosquin Paragon of Plants UBC Botanical Garden Forums Administrator Forums Moderator 10 Years

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    Actually - check that. It doesn't make a statement as to whether it is native to China, though it is certainly present. It could very well be that its presence in China is due to cultivation in antiquity. It seems, however, that its origin is indeed tropical.
     
  4. jamkh

    jamkh Active Member

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    Really, what surprises nature has in store for febble minds. If it were tropical then how do you account for the fact that it does not flower at all. You may claim there is no need as it reproduces vegetatively, but how do they reproduce then before they become domesticated? Good question? Why must they be deliberately defoliated before they can flower? This behavior pattern points more to them being native to the temperate zone.
     
  5. Daniel Mosquin

    Daniel Mosquin Paragon of Plants UBC Botanical Garden Forums Administrator Forums Moderator 10 Years

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    It certainly has a flower, so I'm not certain what you mean when you state that it does not flower at all. There are also many photographs of it in flower with foliage, e.g., Google Image Search for Wrightia religiosa, but I'd be interested to see the source of your information re: requiring defoliation to flower.

    Perhaps the idea that it requires defoliation (if one takes this to be true, though it sounds like it flowers year-round in its native tropical environs) can be explained by this:

    If we are talking about plants in cultivation (e.g., bonsai), defoliation will cause stress for the plant, prompting the plant to flower and fruit as the parent attempts to produce progeny in case it dies.

    Another scenario exists more broadly for plants growing in tropical areas - there are forests specifically called monsoon deciduous, so perhaps it is a member of those forests. If not specifically a member of those forests, the plant can still undergo seasonal stresses due to the effects of the annual monsoon pattern that mirror (at least in terms of events causing stress) the changing of seasons in temperate climates.
     
  6. jamkh

    jamkh Active Member

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    Daniel,
    Perhaps you may be correct. I do see flowers in full bloom on trees that are grown in the ground in nurseries in the tropics, though I never asked the owners whether they defoliate or not. But this I am certain that when pottted up as bonsai, they never flower unless we defoliate them. This comes from my personal experience and my brother confirmed this fact too. Thanks for revealing the idea of moonson deciduous and also we can have drought deciduous too.
    It is true there can be many scenarios to consider and we just got to keep an open mind and learn more.
     

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