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Blog Home : October 2007

- Aspirin and Disease Resistance

For years, a few people have talked about treating sick plants with aspirin (acetyl-salicylic acid). Salicylic acid (without the acetyl group), a plant hormone, apparently triggers an "immune" response, leading to better resistance of the plant to the infective agent. How does a local infection signal the healthy parts of the plant to start defending themselves against infection?

There are a news item (p. 31)and a research paper (p. 113) in the 5 October 2007 issue of the journal SCIENCE on the finding that methyl salicylate (oil of wintergreen) is the messenger substance produced in infected tissue in a plant that is carried through the phloem to all other parts of the plant. There, it is converted by the enzyme SABP2 (an esterase) into free salicylic acid. Salicylic acid is the compound that actually triggers the resistance reaction in the plant.

The news item is at http://www.sciencemag.org/cgi/content/summary/318/5847/31a "At Long Last, Pathologists Hear Plants' Cry For Help" by Mitch Leslie, in SCIENCE, 5 October 2007: Vol. 318, no. 5847, pp. 31 - 32.

The crux of the matter is this: "... Klessig and colleagues came upon what seems to be a real messenger while chasing the receptor for salicylic acid. The team's experiments eliminated one candidate receptor, the enzyme SABP2. However, they discovered that SABP2 transforms methyl salicylate into salicylic acid and that the enzyme is necessary for systemic resistance, suggesting that methyl salicylate might be the signal. ..." according to the news item.

The research paper is at http://www.sciencemag.org/cgi/content/abstract/sci;318/5847/113 "Methyl Salicylate Is a Critical Mobile Signal for Plant Systemic Acquired Resistance" by Sang-Wook Park, Evans Kaimoyo, Dhirendra Kumar, Stephen Mosher, Daniel F. Klessig, in SCIENCE, 5 October 2007: Vol. 318, no. 5847, pp. 113 - 116. Abstract:

"In plants, the mobile signal for systemic acquired resistance (SAR), an organism-wide state of enhanced defense to subsequent infections, has been elusive. By stimulating immune responses in mosaic tobacco plants created by grafting different genetic backgrounds, we showed that the methyl salicylate (MeSA) esterase activity of salicylic acid–binding protein 2 (SABP2), which converts MeSA into salicylic acid (SA), is required for SAR signal perception in systemic tissue, the tissue that does not receive the primary (initial) infection. Moreover, in plants expressing mutant SABP2 with unregulated MeSA esterase activity in SAR signal–generating, primary infected leaves, SAR was compromised and the associated increase in MeSA levels was suppressed in primary infected leaves, their phloem exudates, and systemic leaves. SAR was also blocked when SA methyl transferase (which converts SA to MeSA) was silenced in primary infected leaves, and MeSA treatment of lower leaves induced SAR in upper untreated leaves. Therefore, we conclude that MeSA is a SAR signal in tobacco."

Request reprints from: Daniel F. Klessig at <dfk8@cornell.edu>.

I wonder which would be more effective, applied topically to plants threatened with fungal, viral, or bacterial infections -- salicylic acid or methyl salicylate? Either should be more effective than aspirin. Good gardening,


- Flower Colors: If Reds, Why not Blues?

In pursuing the topic of anthocyanin biosynthesis in flowers I came upon the following.

Using Google Scholar, at http://scholar.google.com/ , I found an interesting old (2001) review of Flavonoid Biosynthesis by Brenda Winkel-Shirley in PLANT PHYSIOLOGY, June 2001, vol. 126, pp. 485-493; see http://www.plantphysiol.org/cgi/content/full/126/2/485 .

Hammett et al. reported that red and orange Clivia flowers contain pelargonidins (for orange and brick-red colors) as well as a bit of delphinidins (purples and blues). The enzymes that convert the chalcone product naringenin to delphinidin precursors are P450 hydroxylases, Flavonoid 3'-Hydroxylase and Flavonoid 3',5'-Hydroxylase (F3'5'H). If Clivia flowers contain delphinidins, then these enzymes are probably present.

Pelargonidin structure

It seems that to get significant production of delphinidins, you need an additional enzyme, a specific cytochrome b5 (cyt b5). Introducing the petunia F3'5'H and cyt b5 genes into carnations converted the red flowers to a deep purple color. The cyt b5 apparently keeps the F3'5'H primed and running.


Labs have also been identifying genes that regulate flavonoid biosynthesis. Already well known were genes R, B, C1, and P in maize and DELILAH in snapdragon. Some newly reported included AN11 in petunia; TTG1 in Arabidopsis, and MP1 in maize. One of these, AN11, seems to regulate another regulatory gene, AN2, in petunia.

The flavonoid biosynthetic enzymes seem to be grouped together in a multi-enzyme complex, anchored to the rough endoplasmic reticulum (rER) -- a site of protein biosynthesis in the cell's cytoplasm. Multi-enzyme complexes are well known in biochemistry, and they seem to be organized for rapid and efficient processing of a multi-step biosynthetic pathway.

To get all the way to the colored pigment molecules, you have to have all the biosynthetic genes working and probably all of the regulatory genes as well. Something in this complicated system is disrupted in the group 1 yellow clivias; something else is disrupted in the group 2 yellow clivias.

Needless to say, I have not absorbed all of this yet! Note that bits and pieces of the puzzle are being found in a wide variety of different plant species, However, most of it is coming from work on Arabidopsis (a cress), which is the species of choice for most plant molecular genticists.

Good gardening,


- Genetics and Dr. Watson

Since we have been talking about genetics and DNA, is might be apropos to mention here a very nice interview with Dr. James D. Watson, Nobel laureate, who with Francis Crick discovered the double helix of DNA over 50 years ago. You can find the interview at:


I only met Jim Watson one time, around 1959 or 1960, when he tagged along with Francis Crick to the University of California Berkeley to give a series of lectures. I was a grad student there at the time, and Jim Watson had time to kill while Crick made the rounds of the big shots' laboratories. Jim dropped by our lab, and my professor introduced us, as two Hoosiers far away from home (Watson had gone to college in Indiana, making him sort of a Hoosier too). He was indeed a callow youth back then, only 6 years my senior; he was very modest and almost shy.

Crick on the other hand on that visit to Cal gave some of the most fascinating and flamboyant lectures I've ever heard in a scientific setting! Crick had an extraordinary way with words, very articulate. They had to move his talks to the largest auditorium on the Cal campus, and even then there was an overflow audience -- and this was at Berkeley, where Nobel prize winners were lurking just around many corners.

Jim Watson is a famous scientist with modest roots and an unfailing ability to speak plainly and simply, telling the actual truth. You won't find that very often in anyone, famous or not, scientist or not.

Good gardening,


- Catching Up

I've been busy catching up. I'm still catching up, now with this blog. I missed some flowers that bloomed a month ago, Sternbergia lutea and Rhodophiala bifida.

Catching Up with Blooms

Sternbergia and Rhodophiala are genera in the Amaryllis Family (Amaryllidaceae). Two of their species, at least, seem to be fairly hardy here in central Indiana. As noted, both are Fall blooming, a handy trait where not too many flowers bloom in autumn.

Sternbergia lutea (c) copyright 2007 by Shields Gardens Ltd.  All rights reserved.
Sternbergia lutea

I have three patches of Sternbergia outdoors in the ground, and all are doing well. One has increased so much that I need to make a note to lift and separate the bulbs next spring or summer. I can make more patches of Sternbergia around the place with them. They seem to be perfectly hardy, but they don't like weed competition.

Rhodophiala bifida (c) copyright 2007 by Shields Gardens Ltd.  All rights reserved.
Rhodophiala bifida (diploid form)

I have one patch of Rhodophiala bifida, the triploid form common in gardens in the Southern States. I just checked on it, and the leaves are up but there were no blooms this year. It is being crowded out by a huge clump of Iris sanguinea (I think). Those will need to be moved next spring if they are to survive. I need to get more of those bulbs and try them in a lot more places.

Lycoris radiata radiata (c) copyright 2000 by Shields Gardens Ltd.  All rights reserved.
Lycoris radiata radiata (triploid form)

A species that is not in bloom this year is Lycoris radiata radiata, also a triploid garden form from the Southern States. I have one patch of it, and the leaves are just starting to come up. There are no signs of blooms this year. It may need some mulch in winter, and it may have suffered from lack of water during our hot and unusually dry summer this year. In 2000, it bloomed in early September here. I usually expect to see it bloom sometime in late October.

Catching Up with Currency

I've also been catching up on the catalogs we issue and our prices. You might not have noticed, but the value of the U.S. Dollar against the Euro, the British Pound, and the Japanese Yen has been falling. It has also fallen against the South African Rand, from ca. 7.2 Rand per Dollar down to 6.56 Rand per Dollar yesterday (according to this morning's Wall Street Journal).

I've had to accordingly adjust the selling prices of plants that we buy from South Africa. That will be painful for anyone who has been putting off ordering one of the beautiful 'Cameron Peach' clivias! I certainly regret this for my part.

This will also affect the costs and hence the prices of future batches of 'Chubb Peach' and of 'Cynthia's Dream' plants, all of which come from South Africa. Eventually it will also affect the prices of Belgian hybrids as well.

Catching Up with Yellow Clivia

I've been reorganizing the group 1 and the group 2 yellow clivia types (in my own mind). For the group 1 gene locus, I see the yellows as "group 1 allele a," and the Chubb Peach plants as "group 1 allele b." The orange allele at the group 1 gene locus we can call "allele w" for wild type. Nice and neat, even simple.

The wild type group 1 plants would be [1w/1w] while the yellow group 1 plants would be [1a/1a]. Cross an orange with a yellow, and all the first generation offspring would be [1w/1a]. Chubbs Peach plants could have either [1a/1b] or [1b/1b] at the group 1 loci, since Chubbs Peach seems to be at least somewhat dominant (but see below). All this is pretty straight-forward.

Here is where it gets a little tricky. For the group 2 yellow gene locus, I see the orange form as "group 2 allele w" (again for wild type); the plain yellow as "group 2 allele a." For the yellows that have orange or pink on tepal edges or at damaged spots, it would be "group 2 allele b;" and for the peaches that are compatible with group 2 yellows, "group 2 allele c."

The group 2 wild type oranges would be [2w/2w] while the unspotted group 2 yellows would be [2a/2a]. If 'Sunrise Sunset' really is a group 2 yellow, then it is probably [2b/2b] since it sometimes gets orange or pink spots on the petals. My guess is that 'Tessa' would be [2c/2c]. What would a [2a/2b] look like? What do things like [2a/2c] and [2b/2c] look like? Only a lot more careful breeding experiments or some DNA work, or both, will settle the questions.

I expect that in the long run we may well find that the "dominant" alleles are actually only partially dominant, or dose-dependant. For instance, I see that the flowers of a few of my Chubb Peach seedlings have a much deeper tint of peach than most of them do. Could these few be [1b/1b] homozygous plants while most are heterozygous forms, [1a/1b]? Or do the more intensely colored Chubbs Peach have a new modifier gene that is responsible, located at a different gene locus?

The usual wild type orange Clivia miniata would by [1w/1w; 2w/2w] in my notation -- homozygous for orange at both genes.

Good gardening,


- Haemanthus Hybrid

Collectors of Haemanthus and Scadoxus rarely are interested in hybrids of any sort. They are generally focussed on the naturally occuring species found in the wild. This narrowness of focus may be leading them to overlook some interesting plants.

There are almost no hybrid Haemanthus in commerce, so far as I know. One nursery in the United Kingdom has offered bulbs of Haemanthus [albiflos X coccineus]. Although at one time sold under the name Haemanthus 'King Alfred', that name properly refers to Scadoxus [puniceus X multiflorus katherinae] as I understand the situation. This Haemanthus hybrid is capable of producing huge leaves, perhaps reaching 8 inches wide by 18 inches long. When it (rarely) flowers, the inflorescence is a pale pink or off-white, and smaller than either albiflos or coccineus usually bloom. Like albiflos, it produces offsets freely, which may be why it got into commerce at all. It is at best a curiosity.

We managed to produce a cross between H. humilis hirsutus (seed or berry parent) and H. coccineus (pollen parent) a few years ago. Those plants have been very interesting as they have grown. One of the first things noted was that the leaves of most of the seedlings had a narrow, deep red line on the margins of the leaves. This is not a trait I have seen in any plants of H. humilis hirsutus that I have grown, but frequently occurs in H. coccineus. That convinced me that at least those plants with red edges were true hybrids rather than accidental selfings of the mother (seed) plant, hirsutus.

Haemanthus hirsutus x coccineus new leaves (c) copyright 2006 by Shields Gardens Ltd.  All rights reserved.
Red Edges on Leaves of Haemanthus [hirsutus X coccineus]

In addition, the peduncle (stem or stalk of the inflorescence) has hairs on it, like the mother plant but quite unlike the pollen parent.

Haemanthus coccineus (c) copyright 2007 by Shields Gardens Ltd.  All rights reserved.
Haemanthus coccineus

Haemanthus coccineus step (c) copyroght 2007 by Shields Gardens Ltd.  All rights reserved.       Haemanthus hirsutus X coccineus stem (c) copyright 2007 by Shields GArdens Ltd.  All rights reserved.
Haemanthus coccineus stem (left) vs. Haemanthus hirsutus X coccineus stem (right)

Haemanthus humilis hirsutus (c) copyright 2007 Shields Gardens Ltd.  All rights reserved.
Haemanthus humilis hirsutus

Last year, the first of this batch of seedling bulbs bloomed. Although the inflorescence failed to develop fully, it was striking in its color. This year, three of the bulbs are blooming. The size is smaller than the inflorescence of either parent, but close to that of hirsutus. The scapes are taller than the coccineus scapes, about like scapes of hirsutus. Most interestingly, the bracts (spathe valves) are a rich burgundy color, quite unlike the bracts of either parent in this respect.

Haemanthus hirsutus X coccineus (c) copyright 2007 by Shields Gardens Ltd.  All rights reserved.
Haemanthus hirsutus X coccineus

Note that the spathe valves ("bracts") are erect and enclose the florets, as in H. coccineus. In H. humilis hirsutus, the spathe valves are green, and much shorter than the florets.

Sources on Haemanthus

The Genus Haemanthus, by Charles O'Neill, HERBERTIA vol. 47, Nos. 1 & 2, p. 137 (1991)
A Revision of the Genus Haemanthus, by Deirdre Snijman, Supplementary Vol. No. 12, Journal of South African Botany, (1984).
The Color Encyclopedia of Cape Bulbs, by John Manning, Peter Goldblatt, and Dee Snijman, Timber Press (2002), pp. 217-222.

Good gardening,


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