Leo, thanks for a wonderful and useful explanation. We neophytes really appreciate this type of information. Shirley Meneice -----Original Message----- From: pbs-bounces@lists.ibiblio.org [mailto:pbs-bounces@lists.ibiblio.org] On Behalf Of Leo A. Martin Sent: Wednesday, April 09, 2014 6:23 PM To: pbs@lists.ibiblio.org Subject: [pbs] Transposons and Color was Virused Bulbs To my understanding, many cultivated flowering plants with colored or white flowers on different plants reveal simple Mendelian inheritance of pigment production. That is, the wild type plant has colored flowers, reflecting one functioning set of color genes on each of the pair of chromosomes governing flower color, whereas white-flowered plants have two sets of defective pigment production systems. Having two of the same gene complexes is referred to as being homozygous and having one normal and one abnormal is referred to as being heterozygous. So, plants having two functioning complexes would be referred to as being wild type homozygous, plants with two abnormal complexes would be referred to as being aberrantly homozygous, and plants with one of each would be heterozygous. In some cases plants having one chromosome with functioning pigment genes and one without functioning pigment genes (heterozygous) have the normal flower color, and in other cases they have paler flowers (think red, white and pink in sweet peas / Lathyrus odoratus.) If two wild-type homozygous plants breed, all their progeny will have normal flower colors (barring new mutations.) If two aberrantly-homozygous plants and white flowers breed, all their progeny will have white flowers. If one wild-type homozygous plant breeds with one homozygous-aberrant plant, all the progeny will be heterozygous, with one normal gene complex and one abnormal gene complex, and all will have colored flowers, since all will produce some pigment. But if two of these heterozygous plants breed, a quarter of their progeny will be wild-type homozygous, a quarter will be aberrantly homozygous, and half will be heterozygous. How them to explain flower color in Bombax ellipticum? (Or perhaps Pseudobombax ellipticum. I haven't read the paper.) This is a tree from Mexico with a large under- and above-ground storage trunk. For years it was in Bombacaceae, but a lot of reassortment has been going on, and I think it is now a kind of cotton. Everybody I know who has been to habitat during bloom season says all the trees have white flowers. Almost all its American relatives have white flowers. But there is a form, planted rarely here and there throughout Mexico, always in cultivation, with red flowers. It can be seen at the four corners of one of the town squares in Tehuantepec, and in at least one private garden each in Oaxaca city. This red form does not have the thick bulbous base of the wild type, and it seems to me the red ones are all cutting-grown. The red form has similar flowers and leaves to the white form. I know there is a red-flowered tree in Bombacaceae from tropical Asia, but the Mexican plant does not look to me like photos I have seen of this species. How to account for a plant with wild-type white flowers and one instance of a red sport? Transposons revealing function in an otherwise-silenced red pigment production gene complex? I don't have the red form so I can't perform crosses to see what happens. I know a number of people in metro Phoenix with blooming wild-type Bombax ellipticum. Leo Martin Phoenix Arizona USA