Yes, the rugosa will do that to some extent - although it's not exactly the same pattern as that of Rosa chinensis. Of course, and while I realize this doesn't change any arguments, rugosa is a far cry from the central Asian representatives of the section. There is actually mounting genetic and chemical evidence that it may be better positioned with R. roxburghii, much more distant from the cinnamon roses. I think that some repeating members of the section can and do a limited bit of throwing flowers from twiggy growth, but they do so very sparingly compared with the ever-growing, ever-blooming China. The reason for this may be due to the differences in genetic control over the once-blooming habit. Whereas limited summer repeat is probably due to incomplete once-blooming regulation (hormones get interrupted by weather, etc.), what we see in Chinas is a complete malfunctioning of any kind of control over blooming. In essence, without a gene telling the plant not to keep on blooming, it just doesn't know when to stop growing and setting flowers: genetic promiscuity. Most repeat-blooming species probably accomplish repeat bloom differently on a genetic level. When we cross the species very complex genetic interactions result, so that two repeat-bloomers might have only once-blooming offspring, or two once-bloomers might have offspring that repeat; every permutation in between is quite possible depending on what's being combined. The genetic control might be very simple in some species, and very complex in others. R. chinensis probably got its ability from a single mutation in a diploid gene, which became homozygous when that plant was selfed. If R. chinensis is a true, reproducing species and there is no evidence of genes from other species in it, it's quite possible the repeat bloom evolved independently in it. I would not consider an almost-sterile triploid to be a good representative of any species, but it is obvious that an autotriploid is a purely derived state - so wherever there's an autotriploid, there's also a diploid from which it came. Autotriploid means all three of its sets of chromosomes are from the same gene pool, and not the result of hybridization - so this would normally occur when an unreduced gamete (either sperm or egg) containing two copies of its chromosomes was mated with a gamete containing the more typical single copy. It doesn't really help us explain where the repeat bloom came from, unfortunately. Did you catch the bit about Rosa gallica being an allotetraploid? That's even more fascinating, because it means this species probably originated as a hybrid of two distinct species. This had already been studied previously, so this amounts to replication - and lends some much-desired credibility to the idea. Very cool!

Ok, here's one for you, my plants will be 2 years old next year, hopefully they'll put on a great show this summer. Guess this plant, botanical and common name please? Sharon

ZM, "if such a stimulus is applied to one part of a plant, might the response be exhibited in only a part of the plant" Very likely, sometimes. However, there is considerable evidence of remote signaling. So, a stress in one part of a plant can trigger a response in other parts. Percy Wright, a Canadian plant breeder, told a story of how "His uncle moved from Saskatchewan had moved west to the Okanagan and for sentimental reasons had grafted some ultra hardy Saskatchewan plums onto a few branches of the peach trees in his orchard. A harsh test winter arrived after a few years which decimated not only the peach crop, but also the trees themselves. Most were killed outright or at the least severely injured. However the peach trees with ultra hardy Saskatchewan plums grafted in the branches had no winter damage whatsoever!" The environmental stress (cold? short days?) was detected by the ultra hardy plums, which then communicated an appropriate response -- presumably to the roots. When they went dormant, the rest of the tree had no choice but to follow. Here's a more recent example of remote signaling: Plant Mol Biol. 2003 Nov; 53(4): 493-511. Rootstock effects on gene expression patterns in apple tree scions. Jensen PJ, Rytter J, Detwiler EA, Travis JW, McNellis TW "Like many fruit trees, apple trees (Malus pumila) do not reproduce true-to-type from seed. Desirable cultivars are clonally propagated by grafting onto rootstocks that can alter the characteristics of the scion. For example, the M.7 EMLA rootstock is semi-dwarfing and reduces the susceptibility of the scion to Erwinia amylovora, the causal agent of fire blight disease. In contrast, the M.9 T337 rootstock is dwarfing and does not alter fire blight susceptibility of the scion. This study represents a comprehensive comparison of gene expression patterns in scions of the 'Gala' apple cultivar grafted to either M.7 EMLA or M.9 T337. Expression was determined by cDNA-AFLP coupled with silver staining of the gels. Scions grafted to the M.9 T337 rootstock showed higher expression of a number of photosynthesis-related, transcription/translation-related, and cell division-related genes, while scions grafted to the M.7 EMLA rootstock showed increased stress-related gene expression. The observed differences in gene expression showed a remarkable correlation with physiological differences between the two graft combinations. The roles that the differentially expressed genes might play in tree stature, stress tolerance, photosynthetic activity, fire blight resistance, and other differences conferred by the two rootstocks are discussed." The stress (fire blight infection) affected the scion, but the rootstock somehow mediated the response. You're right that stress "can encompass a wide range of factors, many of which we might not think of as 'stress'." To paraphrase Forest Gump, "Stress is as stress does." In the broad sense, any sort of change in conditions is stressful. Many kinds of environmental stress are easily tolerated and usefully exploited by plants (or animals) long accustomed to them. However, unfamiliar changes/conditions can provoke more profound disturbances. Changes in photoperiod, for example, are often exploited by plants to provide a trigger for flowering. But when certain plants (e.g., tropical) are exposed to the wide ranging photoperiods of northern regions, they may respond oddly. In its native habitat (Brazil) the beautiful Amaryllis fulgida (Hippeastrum striatum var. fulgidum) bears a cluster of 2-4 flowers on a scape around 18 inches tall. But when the species was first cultivated in Britain in the early 19th century, it changed dramatically. "This specimen was imported by Mr. Harrison, from Brazil, and was drawn at Aighburgh, April, 1832. Some of the leaves measured twenty-nine inches in length and nearly three in breadth; the first flower-stem (bearing eight flowers) attained the height of thirty inches, and would probably have become somewhat taller, but was generously cut for the completion of the present figure; a second scape immediately succeeded it, twenty-eight inches high and having six flowers." By the end of the century, the gigantism was gone. Generations of offspring from the original specimens soon became adapted to the British seasons and reverted to the original "type." Other differences in "stress" are obvious. I was thinking of various species of roses that tolerate very different conditions, and are also stressed by very different conditions. Forest species (e.g., Rosa pinetorum) are weakened by exposure to full sun, whereas R. arkansana thrives in full light. R. rugosa happily tolerates salt spray when grown near the ocean, while others are likely to be killed. Some favor in humus (woodland types) while others grow and flower best in sand. Furthermore, there are distinct "sensitive periods" (or "critical periods") in plant development. An environmental condition that is usually tolerated without much difficulty can become very stressful during a fairly brief period of transition. And one more item that I just found while looking for something else: Biosystems. 1995 ;36 (1):71-7 8527698 Adaptive determinism during salt-adaptation in Sorghum bicolor. H Seligmann , G N Amzallag During adaptation to salinity, plants of Sorghum bicolor showed malformations affecting the leaves in development (DPL). At the end of the adaptation process, the plants were regrouped according to their pattern of DPL response. The distribution of the plant population in different patterns depended on environmental conditions. However, a positive relationship between the frequency of a pattern and its rate of development has been found. Similarly, a negative relation between the frequency of a pattern and the rate of senescence for the same pattern has been observed. The results reveal the existence of an orientation of the plant response towards the patterns with highest developmental rate and lowest rate of senescence. This property is defined as "adaptive determinism". Results indicate that the NaCl acts as a trigger for adaptation to a whole range of environmental perturbations. This suggests that adaptation to salinity is not a pre-programed response of the plants, and may be related to learning processes occurring in animals. Amzallag made some very interesting studies of the effects of salt on sorghum. I just decided to make a bibliography of his papers. Karl Here is a link that might be useful: Salt stress in Sorghum bicolor

I have never done any actual molecular biological analysis of hibiscus genes but I have a little bit of knowledge and some first hand experience breeding hibiscus. I know that the garden varieties will have very dominant traits in any cross. All the fancy grafted hibiscus must be pretty far removed from garden varieties genetically. They also usually need to be grafted onto stronger, hardier root stock, which often ends up being a garden variety cultivar. I have a few crosses that were successful. Just today in fact, I have a first bloom from one of my seedlings. It is a cross between Ft. Myers (f) and White Wings (m). The flower on the offspring plant is a pinwheel just like W. Wings but instead of being white with a deep red center, it is pink with a deep red center. If anything, the only thing that is different about the seedling is that its leaves are much larger than those of either of the parents. I don't know if this seedling is worth anything, though I don't ever recall seeing this flower anywhere. It looks like Painted Lady, only in pinwheel form and with a smattering of white on each petal. At some point, someone told me not to bother crossing garden varieties because all the offspring will have plain red flowers (wild type). This has turned out not to be the case. Each cross is almost a toss-up as to what you will produce...hence the excitement and fun of breeding H. rosa-sinensis (which is already a hybrid itself).