High light intensity may help protect your plants from viruses

henry_kuskaFebruary 24, 2012

The following paper (which followed up earlier reports) demonstrates that high light intensity enhances a plants immune system. Thus, if you decide to try to "clean" a virused rose by using buds or cuttings,I suggest that: in addition to selecting the cuttings from a plant exposed to the maximun heat of the summer that you also subject the plant to high light intensity. Although this paper is not on specific viruses known to infect roses, behavior from model plants is often very useful in understanding behavior in other plants. This is a suggestion for research. Not a "proof".



Here is a link that might be useful: 2010 reviewed scientific paper

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Campanula UK Z8

What do you mean by 'high light intensity' - amount of lumens, red light, blue light, high pressure sodium, halide? I do a fair bit of growing under artificial light so I am well aware how plant behaviour can be affected. What exactly do you mean by immune system - or is this another term for adaptability, similar to human antibody production.Also, how do you clean a virused plant using cuttings? My experience of virus, admittedly not any which affect roses, has been that they are generally systemic, even though not all of the plant shows an apparent effect, it will still be infectious throughout the plant. My blackcurrants are always at risk of reversion virus because other plot holders are slack about removing plants which have been affected by big bud mite....and the inevitable reversion virus which follows. Usually, I have to toss them on a five yearly cycle as I cannot find any way of preventing this apart from continual replacement of stock.
I started to read the article and quickly admitted defeat feeling like a thicko.

    Bookmark   February 24, 2012 at 11:46AM
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strawchicago 5a IL(zone 5a)

Thank you for that paper, Henry. Ultraviolet light kills germs, and is recommended for sterilizing bottled water in Third World countries. Lack of sunlight, and vitamin D, is also a factor in cancer rate.

When my neighbor put in a fence that blocks the sunlight from the lower trunk - my peach tree has bad fungi infestation, and so does my corkscrew willow. The other corkscrew willow tree with more sun is not affected.

    Bookmark   February 24, 2012 at 12:52PM
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The first question that I will attempt to answer is: "What exactly do you mean by immune system - or is this another term for adaptability, similar to human antibody production."
The general understanding that plants have immune systems (and that the immune system can be more effective at high temperature than at low temperature) is a rather recent development. I have attempted to summarize the scientific research behind this concept in a web page article. See below:
The following link gives a general summary: "Plants possess active and passive means of preventing virus infection. Passive defenses are due to the failure of the plant to produce one or more host factors required for virus reproduction and spread within the host. Active defenses include detection and destruction of the virus-infected cells due to the function of specific resistance genes in the plant. Normally, resistance genes are active only against a particular virus. In addition, plants possess a general defense system that is somewhat analogous to the animal immune system. The major difference between the two is that the immune system in animals targets a pathogen’s proteins, whereas the plant defense system, which is called RNA silencing, detects and degrades viral RNAs (Wassenegger and Pélissier 1998)."

RNA SILENCING is the key expression if one is interested in doing a Google search.

Here is a link that might be useful: My web page article on temperature dependent immune system

    Bookmark   February 24, 2012 at 2:12PM
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These comments are directed towards the the question:
"Also, how do you clean a virused plant using cuttings? My experience of virus, admittedly not any which affect roses, has been that they are generally systemic,"
It is common to read in the general rose virus reviews something along the lines of the following: "Cuttings from an infected plant will be infected - no matter what portion of the plant they were taken from. The disease is systemic: The entire plant is infected, whether visible signs of the disease are present, or not." see as one example:
A Cornell 1998 rose virus research paper (not in the cited abstract:
The statement is in the "must be paid for" full paper.) stated: "Virus distribution in apple, plum, and cherry trees is irregular" (they then give 1963, 1973, 1984, and 1986 references.) it is likely that virus distribution in rose is also irregular. This explanation appears to be reasonable since virus inoculated plants frquently exhibited some shoots expressing no symptons. It is possible that the virus has not been distributed throught the plant."
Since then, one French http://apsjournals.apsnet.org/doi/pdfplus/10.1094/PHYTO.2000.90.5.522
and one Polish study
have confired the irregular distributions.
The French reported that: "A total of 89% (59 out of 66) of Anna stems was entirely PNRSV negative when axillary shoots from these stems developed after the decapitation of the floral stem, after the development of cuttings, or grown in vitro were tested by ELISA. ELISA tests of leaves from these stems were all negative. Since IC-RT-PCR conducted in parallel on all the explants from three (out of seven) of these stems also were negative, we suspect that these stems were virus free, even if they belonged to infected plants, or that the viral titer was very low in the stems."
Thus, the French reported that they suspect that they were able to obtain clean plants from cuttings (as determined by the use of ELISA or PCR). They leave the door open that a more sensitive method may find a low amount of infection.
This is what was reported concerning California Davis ROSE VIRUS experience:
"Oddly enough, one way they eliminate virii is by clonal propagation. Simply put, if you culture enough buds (~100) some small number of them (two or three maybe) will be virus free. The drawback is space, labor and the need to index all the test plants."

See the following thread for a discussion of the possibilities of cleaning cuttings in a hot climate.

Here is a link that might be useful: garden web thread on possibilities of cleaning cuttings

    Bookmark   February 24, 2012 at 3:54PM
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Now on to the remaining question: "What do you mean by 'high light intensity' - amount of lumens, red light, blue light, high pressure sodium, halide?"
H.Kusks comment: they report using: " "High Light" intensity (HL) and "Low Light" intensity (LL) conditions used here, refer to 130 � 20 �mol m-2 s-1 and 35 � 15 �mol m-2 s-1 continuous white light, respectively."

"Plants grown under blue light in comparison to red light grown plants, showed a higher frequency of systemic silencing although this difference was not found to be statistically significant (see additional file 2: Table S7)."

As an aside this paper supports earlier observations: " Our findings are in agreement with older virological observations where plants exposed to reduced light intensity became more susceptible to virus infections [45]. Furthermore, it had been shown that light intensity and quality influence the number of local lesions caused by plant viruses [51,52]."

Concerning The amount in lumans and the source. The following may be useful:


Concerning the source of white light: "Plants were grown in a chamber of 70% relative humidity and 22 � 0.5�C temperature. Illumination was provided as continuous white light under a panel of cool-white fluorescent tubes (TL-D, 50 W/84o HF, Electronic NG, Phillips, Holland) at a photosynthetically active radiation (PAR: 400-700 nm).

    Bookmark   February 24, 2012 at 4:19PM
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