Rootstocks and Flower Color

Roses for Hybridizing Founder Hybrids
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I found this item that seems to fit here as well as anywhere. Simply stated, silicon seems to be broadly beneficial, and the ability to absorb it through the roots varies among species, as does the ability to accumulate it.

I have no details yet about Rosa species, but in some cases the reported disease resistance may be due to silicon uptake and accumulation.

Silicon in Plants: Advances and Future Prospects (2016)
edited by Durgesh Kumar Tripathi, Vijay Pratap Singh, Parvaiz Ahmad, Devendra Kumar Chauhan, Sheo Mohan Prasad

7.2.13 ROSE

Mist applications of sodium silicate to rose (Rosa hybrida L.) cuttings decreased leaflet drop and increased rooting (Gillman and Zlesak, 2000). Si alleviates salt stress, decreases malondialdehyde content, and affects the petal color of salt-stressed cut roses (Reezi et al., 2009). The addition of Si to recirculated nutrient solution in a closed hydroponic system ameliorated most of the negative effects of recirculation on cut rose (Rosa hybrida L. ‘Kardinal’) production, improving stem quality (Ehret et al., 2005). Hwang et al., (2005) reported that applications of potassium silicate had beneficial effects on the growth and quality of cut flowers of the miniature rose ‘Pinocchio’ in a rockwool culture system. The incidence of powdery mildew in Rosa hybrida ‘Remata’ from the infection of Sphaerotheca fuliginea significantly decreased with 100 mg/L K2SiO3 applied as foliar sprays, compared to that in the control (0 mg/L K2SiO3) (Park et al., 2013).

7.3.1 POSITIVE EFFECTS

The positive effects of Si observed in monocots have generated interest for research with floricultural crops as well. The reported effects vary and depend strongly on plant species. Horticultural crops grown in Si-amended substrates exhibit a variety of responses related to abiotic and biotic stresses and morphology (Mattson and Leatherwood, 2010). The effects have been associated mainly with Si deposition in cell walls and as a double layer of polymerized Si in the cuticle, which presumably passively impedes evapotranspiration (Ma and Takahashi, 2002) and provides a mechanical defense against pests and pathogens (Helanger et al., 1995). Si, being dispersed through the plant via the transpiration stream (Samuels et al., 1991), inhibits fungal diseases through modifications of the epidermal layer of the leaves and fruits, as well as by increasing the presence of low-molecular-weight metabolites (Fawe et al., 1993; Gillman et al., 2003). Si alleviated salt stress by modulating antioxidant enzyme activities in Dianthus caryophyllus (Soundararajan et al., 2015). Si has many effects, which include improving the cell wall thickness below the cuticle and also the leaf angle, making leaves more erect, and thus reducing self-shading, especially under a high nitrogen rate (Mauad et al., 2003).
http://bulbnrose.x10.mx/Roses/breeding/SiliconRoses2016.html

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Now that the days here are pleasant-to-cool, and the nights brushing against freezing, it is interesting to note that ‘Iceberg’ is growing and blooming to beat the band. ‘Burgundy Iceberg’ is also blooming, but not quite as enthusiastically as ‘Iceberg’.

To be fair, there are several specimens of ‘Iceberg’ in the garden I visit most often. A few of the ‘Iceberg’ specimens are not doing as well as the ‘BI’. Bud selection is certainly called for.

Of course, a cultivar that grows and blooms so happily at low temperatures might not do as well in the north, where winter dormancy is desired.

How far north does ‘Iceberg’ thrive?

30 Dec. 2018

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A little off topic, but is related to propagation.
The fact that roses can be propagated from a single eye has been known since the early 19th century. Micropropagating from a two bud cutting is not such a big deal by comparison. However, the author (Kane) included an interesting comment.

In vitro-produced flowers are smaller and have fewer petals than these produced on plants grown in the greenhouse.

‘Rosette Delizy’ was the first true Tea rose I ever grew. (RICA Sombreuil is lovely, but not a Tea). Alas, ‘Rosette Delizy’ is too, too double to be useful for breeding. I checked on it time and again in San Jose, but never saw a stamen or a pistil. I don’t know that in vitro propagation from a bud would help it produce a bloom with fewer petals, but you never know. And I’m guessing that there are other too, too double roses that might release a bit more pollen if forced to bloom on tiny plants.

Micropropagation and in vitro flowering of rose
Michael E. Kane

in Plant Tissue Culture Concepts and Laboratory Exercises (1999)
edited by Robert N. Trigiano

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I’m finding similar results with several Teas here in the coolth of the Central Coast, Karl. I wonder how they would be in the higher inland heat? I had wondered about the accuracy of using Rosarium Uetersen for breeding as in the inland valley heat there were no sexual parts, only petals and petaloids. We grew and sold hundreds of that monster and none of them set hips nor expressed any sexual parts. Then, I saw it grown along the coast where it was not only a completely different color (pastel coral instead of the Peter Max, DayGlo, fry-your-retinas, Neon posterpaint coral of the hot weather) but semi double with a center FULL of stamen and anthers. The only difference was climate. Why not with the Teas?

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At the Heritage Rose Garden (San Jose), the color was more “soft coral” than “flashing neon”. The pics I have show double flowers with pistils peaking through. The pics were shot in September, so there’s that.
http://bulbnrose.x10.mx/Roses/Rose_Pictures/R/RosariumUetersen.html
Karl

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I have noticed, here in SoCal, that some specimens of ‘Iceberg’ bear blooms with a light pink flush in cool weather, while other specimens growing nearby do not. I will guess that those that already flush pink would be more likely to “sport” to pink if repeatedly selected.