Baccará (HT) [Happiness x Independence]

August 16, 2009 - SJH

June 13, 2009 - SJH

September 28, 2008 - SJH

November 25, 2006 - SJH

December 23, 2000 - SJH

- SJH

Journal of Experimental Botany (25)4: 614-623. (1974)
Factors Determining Petal Colour of Baccara Roses I. The contribution of epidermis and mesophyll
I. Biran, M. Robinson and A. H. Halevy
The partition of light radiated on to the outer epidermis of a Baccara rose petal or on to an intact petal was examined. Most of the red light was either reflected or transmitted whereas other wavelengths and especially the green range were absorbed. When the total amount of light transmitted (epidermis) or reflected (intact petal) increased, a rise in the blue range was recorded and the colour of the petal, determined objectively by CIE or Munsell's method, became more purple.
    Examination of the partition of light in the different layers of the petal revealed that light reflected from the outer epidermis is made up of two parts; one part is reflected directly and the other part is first transmitted through the epidermis, reaches the mesophyll, is reflected from it and is then transmitted through the epidermis. This latter part causes a shift in colour from purple to red.
    Colour differences between different petals on one flower and different parts of the same petal were defined objectively. The change from red to purple colour was connected with vigorous growth of either the petal or epidermal cells, respectively.
    The contribution of the mesophyll in changing the reflectance curve of petals is explained and it is suggested that although the mesophyll is colourless, it contributes to a great extent to the changes occurring in petal colour.

Journal of Experimental Botany 25(4): 624-631. (1974)
Factors Determining Petal Colour of Baccara Roses II. The effect of pigment concentration
I. Biran, M. Robinson and A. H. Halevy
'Blueing' in young and senescing petals was compared in the red rose cv. Baccara. The 'blueing' of senescing flowers is accompanied by a bathochromic shift in the light reflectance curve, a rise in the pH value and a decrease in the malic acid concentration of the petal tissue. These factors indicate that a complex with a co-pigment is produced. Similar changes were not found in the 'blueing' of young flowers, where a decrease was found in pigment concentration per unit weight as well as per unit area of petal. A similar 'blueing' was achieved by diluting a solution of crystalline cyanin. The phenomenon of 'blueing' by dilution is discussed in the light of Bougeur's law.

Journal of Experimental Botany 25(4): 632-637. (1974)
Factors Determining Petal Colour of Baccara Roses III. Effect of the ratio between cyanin and pelargonin
I. Biran, M. Robinson and A. H. Halevy
The changes in colour and in the pigment concentration of the two sides of Baccara rose petals which occur when plants are grown under various temperature regimes, were examined. The inner side of the petal is redder and the predominant pigment is pelargonin whereas the outer petal surface tends to 'blue', and, the predominant pigment on this side is cyanin. The cyanin:pelargonin ratio on the outer side of petals increased three-fold under the influence of low temperatures.
    The outer surface of petals growing for a long period under low temperatures was 'blue' when compared with the red petals which had been subjected to low temperatures for a short period. The cyanin:pelargonin ratio of 'blue' petals was higher than that of red petals. Total pigment content was similar in both types of petal. Flowers grown under high temperatures 'blued' without a concomitant fall in the cyanin:pelargonin ratio.