In reading the early descriptions of Rosa rugosa
and its varieties, I began to wonder whether the needle-like prickles (glandular acicles) were derived from trichomes. A quick search turned up this:
Understanding Plant Anatomy, p. 123 (2009)
By S. R. Mishra
"Prickles are classified as trichomes, no matter how massive they may be, whenever it is clear that they arise from the epidermis and are not modifications of any other organ.
As a matter of fact, the large prickles of Rosa and the vascular prickles on the fruit of Horse Chestnut are connected with simple hairs by all gradations of finer prickles."https://books.google.com/books?id=ZAQAq ... &q&f=false
Trichomes are a fascinating subject on their own. Beal (1878) described and illustrated some of the diversity of structure and function he found among trichomes of various plants.https://www.jstor.org/stable/2448153?se ... b_contents
And Cannon (1909) compared the trichomes of some hybrids with those of their parents.http://www.biodiversitylibrary.org/item ... 1/mode/1up
Pondering this information, I remembered a very curious curiosity I read about years ago, Begonia phyllomaniaca.
Could there be a connection between the proliferation of small leaves on stems and leaves of this begonia? Yes, according to Smith (1919).
"My observations contradict those of Prillieux and confirm those of Verlot and of Caruel that buds may arise from the ordinary trichomes. They may develop either from the base or the middle of acicular hairs. Such hairs arise from a red tissue, the other parts of the epidermis being green. I have also seen them developing from the base of glandular hairs which are abundant on the young internodes, but they are not restricted to these pairs."http://bulbnrose.x10.mx/Heredity/Begoni ... a1919.html
Another item I found several years ago is also of some interest. MacDougal (1903) noted that the orchid Cypripedium montanum
normally produces two types of trichomes, the pointed and the knobbed.
So, the various types of trichomes (and their derivatives) are largely independent in their heredity and in their environmentally modified expressions.
Which brings me to the Rose matter.
Les Roses, pp. 47-48 (1817)
It is from one of our drawings that this Rose [R. kamchatica] has been engraved for the garden of CELS, page and figure 67. By comparing this individual with that which accompanies our description, it will be easily seen that in less than eighteen years, this rose has undergone considerable modifications in the length or density of the spines, and in the shape of the leaflets.http://bulbnrose.x10.mx/Roses/Rose_Pict ... atica.html
In fact, this Rosa kamchatica
had become as "fierce" as R. ferox
Lawrance. The above link shows Redouté's two illustrations, along with the one from the Botanical Register.
My suspicion is that the original population of R. kamchatica
is polymorphic for a gene (or two) that allow for an extreme development of the glandular acicles, but the trait is suppressed by some environmental condition active in Kamchatka. When various specimens are moved further south, some of them become "fierce" while others don't. This suspicion is not contradicted by Palibin (1899) who noted that Rosa rugosa
is widely distributed, but is NOT found in Kamtschatka.https://books.google.com/books?id=53g1A ... &q&f=false
Another example of morphological traits being expressed differently under different environmental conditions was noted by Hurst.
Experiments in Genetics (1925)
Charles Chamberlain Hurst
Chromosomes and characters in Rosa and their significance in the origin of species
In the most complex case studied, in the octoploid species BBCCDDEE (R. acicularis
Lindl.), the four double septets seem to work more or less in relays in different parts of the plant at different times and seasons, resulting in a periodic predominance of one septet over another in certain parts of the plant, the general result being more or less a mosaic of the four septets of characters arranged end to end or side by side.http://bulbnrose.x10.mx/Roses/Hurst/HURST2.HTM
Naturally with four double septets working equally and independently in an octoploid species, only about one-fourth of the characters of each septet can be represented at one time.
One final note on the function of glandular organs:
ACTA AGROBOTANICA, Vol. 67 (4), 2014: 13–24
© The Author(s) 2014 Published by Polish Botanical Society
CHARACTERISTICS OF THE SECRETORY STRUCTURES IN THE FLOWERS OF Rosa rugosa Thunb.
Aneta Sulborska, Elżbieta Weryszko-Chmielewska
A b s t r a c t
Due to the presence of secondary metabolites exhibiting pharmacological activity, the flowers of Rosa rugosa
Thunb. have found application in traditional and folk medicine. The essential oil obtained from them is also considered to be a phytoncide. The morphological and anatomical characters of glandular trichomes located on the sepals of R. rugosa
were studied by light and scanning electron microscopy. Using histochemical tests, the type of secretion produced in the trichomes was determined and its contents were compared with the secretion produced by the papillae on the petals.http://agro.icm.edu.pl/agro/element/bwm ... -SM_13.pdf