February 2010 – Page 3 – The Garden Professors™

A rose by any other name…

This past week I got to spend three days doing one of my favorite things; talking about conifers. Wednesday I was a last-minute guest lecturer for a landscape design class and Thursday and Friday I did my ‘Conifers for Connoisseurs’ talk for our MSU Extension ‘Plants of Distinction’ program. One of my favorite conifers and one I often recommend as a large specimen tree is Alaska yellow-cedar (the name I learned in Mr. Chance’s Botany class at Olympia High School) or Nootka false cypress (the usual common name for the tree in this part of the world). Notice that I didn’t give a scientific name, like a good garden professor should. The reason? I’m not 100% sure what the scientific name for Alaska yellow cedar is any more.

Xanthocyparis nootkatensis at Daisy Hill Farm, DeWitt, MI

Prior to 2000 it would have been easy: Chamaecyparis nootkatensis. Then a team of international scientists including members of the Kew Royal Botanic Gardens and the Missouri Botanical Garden discovered a rare conifer in northern Vietnam, which was previously unknown to science. The new species was described in a 2002 article by Farjon et al as Xanthocyparis vietnamensis. A conifer still unknown to science at the end of the 20^th Century, that’s pretty cool. But, in addition to describing and naming the new species, the authors’ also reclassified Chamaecyparis nootkatensis with the new species as Xanthocyparis nootkatensis. While this news was mildly disappointing to those of us who love the tree and thought Chamaecyparis nootkatensis was about the coolest scientific name ever, the name change was not entirely surprising. Within the genus Chamaecyparis, nootkatensis was always the proverbial red-headed step-child. At one point the species had been grouped in the genus Cupressus. The change to Xanthocyparis also required a change for Leyland cypress, an intergeneric hybrid between Alaska yellow cedar and Monterey cypress (Cupressus macrocarpa). Under the new nomenclature ×Cupressocyparis leylandii becomes × Cuprocyparis leylandii.

Now, as if all this weren’t confusing enough, subsequent work by Damon Little based on molecular markers groups all of the Cupressus species in North America and the two Xanthocyparis species under one genus, Callitropsis. Little et al’s re-classification and rejoinder by Mill and Farjon (2005) demonstrate the schism which has developed between taxonmists that rely heavily of cladisitcs and molecular tools and those that rely on morphology and evolutionary relationships. Their debates are far testier than any barbs traded between Linda and the Brothers Horvath. Check out this link for a taste of the action:

http://urhomology.blogspot.com/2009/03/myths-that-evolutionary-taxonomists.html

Xanthocyparis nootkatensis at MSU Horticultural Gardens

So what about us poor horticulturists and foresters who just want to know what to call the damn thing? I suspect the taxonomic battle lines will deepen before anyone offers a peace offering. And this will extend far beyond Xanthocyparis (syn. Callitropsis). Get used to seeing lots of synonyms next to scientific names in the future. Remember when you took your first Botany class and learned we used scientific names to eliminate confusion over common names? Sigh… Alaska yellow-cedar sounds pretty good to me.

Farjon, A., N.T. Hiep, D.K. Harder, P.K. Loc, and L. Averyonov. 2002. A new genus and species in Cupressaceae (Coniferales) from northern Vietnam, Xanthocyparis vietnamensis. NOVON 12:179-189.

Little, D.P., A.E. Schwarzbach, R.P. Adams, and C.-F. Hsieh. 2004. The circumscription and phylogenetic relationships of Callitropsis and the newly described genus Xanthocyparis (Cupressaceae). American Journal of Botany 91(11): 1872-1881

Mill, Robert R. and Farjon, Aljos. 2006. Proposal to conserve the name Xanthocyparis against Callitropsis Oerst. (Cupressaceeae). Taxon 55(1):229-231

Friday puzzle untangled

Well, either the puzzle was too easy or you guys are too smart! Deb, Christopher, Lori, Foy, Jim, and Hap go to the head of the class – it was, indeed, staking material left on way too long. Here’s a photo from over 10 years ago. I’m not sure this is the very same tree, but it’s from the same parking lot/torture chamber:

I “liberated” these trees with my handy wire-cutters (never leave home without them) shortly after taking the pictures. Several take-home lessons from this example:

1) Plastic tubing does not protect bark from girdling wire injury

2) Parking lot trees, even in very upscale shopping malls, are abysmally managed

3) Trees are amazingly resilient

Have a good week!

Friday quiz…better late than never!

As you know, I wanted to get something intriguing for this week’s puzzler from the NW Flower and Garden Show. Alas, there was nothing that jumped out at me, so I’m digging into my photo archives.

Here is a recent photo from a parking lot tree. About four feet up the trunk, I found this interesting growth. No, I don’t know what the tree species is because (a) it wasn’t in leaf and (b) I’m a taxonomy klutz. But I can assure you that the odd bark morphology has nothing to do with genetic identity.

I can also assure you that there is no foreign material under the bark that’s causing this phenomenon. The question: what DID cause it?

The answer – and a revealing photo – on Monday!

Friday quiz…yes it’s coming

As you might know, I’ve been at the NW Flower and Garden Show this past week, and yesterday I had two seminars to give. So I didn’t have a chance to post a quiz, and this morning I’m back over for a few hours before I’m done.

I’m hoping to find an interesting Garden Prof question topic at the show, so I’m taking the camera today. If I can’t, I have a backup. But I promise there will be a question up by today!

Plant Patents

I love patents. In fact, I once wrote a novel based on a patent — It was called Patent 22 — If you look this patent up you’ll just find a piece of paper from 1915 which says, essentially, that a search was made for the patent but that it couldn’t be found. No one wanted to publish it — and reading it now I do realize that it does need some serious work. Still, I think this little tidbit gives you a little bit of an idea about my interest in patents. (The paper on file at the patent office is below):

Anyway, here’s the thing that people don’t know. There are three ways to protect a plant from someone else “stealing” it: Plant Patents, The Plant Variety Protection Act, or a Utility Patent (which is what you or I usually think of when we think of a patent). The Plant Patent Act passed in 1931 and it is the way that most plants are protected today. Plants like the Honeycrisp apple which are propagated vegetatively (using cuttings or grafting) are usually protected with this type of patent. The second type of protection is the Plant Variety Protection Act of 1970. This Act lets you protect seed propagated plants. With these two types of protection you wouldn’t think that any other type would be needed — but the Supreme Court has twice ruled that plants can be protected using Utility patents (once in the 1980s and once in the early 2000s). So, what is the problem with that? Well, basically, the problem with that is that, while the other ways to protect plants allow for the use of those plants in research or for breeding and farming, using a utility patent prevents anyone from using the patented plant from doing anything with that plant without permission from the patent holder. And, basically, an entire species of plant can be patented — it has been done before with a bean that someone brought from Mexico into the US — he cornered the market on the bean and noone could sell or breed the bean without his OK. Sounds insane doesn’t it? Just my first thought on a cold Thursday morning.

Water droplets and burned leaves, continued

A few weeks ago (January 20 – “Help, help, the sky is falling”) I started a discussion about an article appearing in the peer-reviewed journal New Phytologist. That posting focused on the methodology and results in the paper. Today let’s take a look at the authors’ underlying arguments (their introduction to the study) and their conclusions.

1) The authors’ premise is that “laymen and professionals alike commonly believe water drops on plants after rain or watering can cause leaf burn in sunshine.” To support this statement, the authors surveyed “relevant topical websites.” They found 29 sites (primarily .org and .com, but no .edu sites) that agreed with this statement and 9 sites (including 4 .edu sites) that disagreed. How this translates to “professionals” believing that water drops cause sunburned leaves is unclear, especially when all the .edu sites surveyed disagreed. In my opinion, the authors should have surveyed ONLY .edu sites to test their hypothesis about what professionals believe. And why only 38 sites? We’re not told how or why these sites were selected.

2) Building on this shaky premise, the authors then address the apparently popular concern that water drops can cause forest fires. They survey “the forestry literature” to find “the prevailing opinion is that forest fires can be sparked by intense sunlight focused by water drops on dried-out vegetation (Table S3).” Table S3 is not included in the online article but is in a supplementary file. Happily, it is short enough that I can paste it in here (so you can find the sites yourself):

Table S3 Survey of websites discussing the possibility of forest fires due to sunlight focused by water drops. We posed the question: “Can sunlit water drops spark forest fires?” The rate of the ’yes’ answer was 3 / 3 = 100%.

URL	Title of article	Answer
URL	Title of article	yes	no
http://fotozz.hu/fotot_megmutat?Foto_ID=30936	Forest fire and water drops	+
http://mek.oszk.hu/01200/01214/01214.pdf	Radó (2001) Role of vegetation in protection of the environment	+
http://wiki.answers.com/Q/Whether_presence_of_water_cause_forest_fire	Whether presence of water cause forest fire?	+

I must say this took my breath away. This is not a survey of the “forestry literature.” It is 3 websites, two in Hungarian and one in English, chosen for unknown reasons. The first site is actually a stock photo website with comments about pictures of water drops on leaves. The second is entirely in Hungarian and is not in the scientific databases. The third is in English, and here’s what “wiki answers” has to say:

“When I was a youngster and could not afford a magnifying glass, I would twist a piece of wire around a pencil so that it formed a round piece at the end of the wire. I would then dip the rounded end into water so that a blob of water made a very small magnifying glass. I suspect that when it has rained this same effect is left on leaves, millions of tiny magnifying glasses all concentrating the suns rays onto what they happen to land on. Just one tiny focal point of a rain drop could possibly generate enough heat to start a fire. Robert”

[Note to the editors at New Phytologist: What I really want to know is how this kind of junk science can slip through peer review. It is embarrassing.]

3) The authors (none of them plant scientists) nevertheless address plant ecophysiology in the discussion: “If, after rain, leaf blades were covered by a water film, they could not breathe, because gas exchange through the stomata would be blocked…To avoid this, plants evolved efficient water-repelling and water-channeling structures which build up and roll off rain drops. For example, water drops easily roll off the highly hydrophobic leaves of lotus, Ginkgo (Fig. 2b), and floating fern (Fig. 3b,c) if leaves are tilted or shaken.”

Two comments here: the stomata through which terrestrial plants “breathe” are primarily on the underside of the leaves. It is true that floating aquatic plants have most of the stomata on the upper leaf surface. Which leads me to ask…if water drops easily roll off of floating fern leaves, then how did the researchers do the following? “…the experiment was concluded by cutting and scanning several Salvinia leaves – still holding water drops – in the laboratory in order to document their sunburn.”

4) The conclusion of a research article, as any Garden Professor knows, is meant to summarize the results of the experiment. Yet the last paragraph of the conclusion reads as follows: “Lastly, a similar phenomenon might occur when water droplets accumulate on dry vegetation (e.g. straw, hay, fallen leaves, parched grass, brush-wood) after rain. If the focal region of drops falls exactly on the dry plant surface, the intensely focused sunlight could theoretically spark a fire. However, the likelihood of this is considerably reduced by the fact that after rain the originally dry vegetation becomes wet, and as it dries water drops also evaporate. Thus, claims of fires induced by sunlit water drops on vegetation should also be treated with a grain of salt.”

Even though the authors seem to discount the possibility of these scenarios, they did NOT test the ability of water drops to cause combustion. This speculation really belongs in the discussion, if anywhere at all. So why is does it make up 50% of the conclusion? The cynic in me says it’s because 90% of the people looking at this article will read only the abstract and the conclusion – and this is especially true of nonscientists. It’s a great way to get immediate attention, even with a complete lack of supporting evidence.

Don’t believe me? Just type in “water drops cause forest fires” without the quotes into Google. 146,000 hits, and all the top ones reference this article.

All Right, Linda; I’ll See Your Paraheliotropism and Raise You a Nyctinasty

Amicia zygomeris is a cute little herbaceous thing I picked up on a visit to Plant Delights nursery back in October. For $13, I wanted to be sure it survived the winter, so it’s been in our kitchen garden window, just waiting for spring.

Soon after putting it in the window, I had an “oh no, I’ve killed it” moment one evening. All the leaves were drooping, yet the soil was moist. The next morning, it seemed to be back to normal. The following night, droop city again.

Ah HA! Nyctinasty* at its finest – plant movements to the circadian rhythm. Tropisms are growth responses, while nastic movements are just that – reversible movements. There are other “nasties” out there – photonasty is movement in response to light, hydronasty – water, etc. The classic example is Mimosa pudica – sensitive plant – the little leaves fold to the touch (thigmonasty).

Legumes are particularly prone to this – check out the bean plant flapping its leaves in time-lapse video at the “Plants in Motion” website (U. of Indiana Biology Department). The movement comes from changes in turgor of the cells that attach the leaf petiole to the stem. This spot’s called the pulvinus – think of it as the leaf’s armpit. What do plants gain from this daily spreading then folding of leaves? Folks have been pondering this for centuries. Darwin wrote about it in “The Power of Movement in Plants” (1880). Though the biochemical mechanism has been discovered, I don’t believe any conclusions have been reached as to "why".

Amicia zygomeris in the evening. The common name, courtesy of Tony Avent, is “Gotta Pea". I am not making that up.

*BTW, Nyctinasty is also the name of a pop band from Manila. Must be a biologist or two in the bunch.

Checking up on FreezePruf

As winter continues to hold its icy grip over the middle of the country, our thoughts don’t stray too far from plants and cold. Recently one of the graduate students in our department, Nick Pershey, brought to my attention a new product called FreezePruf that claims to improve plant cold hardiness by up to 9 degrees F. Since a couple of degrees of improved cold tolerance can be a big deal (just ask a Florida citrus grower after a 29 deg. F night), nine degrees F. is huge. At first blush, FreezePruf looks ripe for the Garden Professors’ picking. The promotional claims are sensational and are followed by the obligatory exclamation points. “Just spray it on. It’s like moving your temperature zone 200 miles south!” So the obvious questions are: What is it? What does it do? Does it work?

What is it? FreezePruf is a mixture of several fairly common compounds. These include WiltPruf (a film-forming anti-transpirant), SilWet (a surfactant – helps material spread and stick to leaves), AgSil (potassium silicate), polyethylene glycol (an osmoticum – PEG is widely used in cosmetics and laxatives), and glycerol.

What does it do? To understand what FreezePruf does it’s helpful to understand how freezing injury occurs in plants and how plants tolerate freezing. First, remember that water exists in plant tissues between plant cells (extracellular) and within cells (intracellular). When plants are exposed to freezing temperatures ice forms first between cells (extracellular ice) but not within the cells. This is due to the fact that water within cells contains solutes that depress the freezing point. Freeze damage can occur in a couple ways. One is ice formation within cells (intracellular ice). Tissues can also be damaged if cells become excessively dehydrated as a result of extracellular ice formation – the ice between cells acts like a salt or osmoticum to continue to draw water of the cell and into the intercellular spaces. The formulation of FreezePruf apparently acts to depress the freezing point within the cells (due to potassium ions and PEG) and to limit cell dehydration.

Does it work? At present the only data available on FreezePruf is from the product developers in their patent application. To date, nothing on the product has been published based on peer-reviewed studies; which always makes the Garden Professors skeptical. The product development team, however, is lead by Dr. David Francko, a plant biologist and Dean of the Graduate School at the University of Alabama. Data in the patent application show improved cold hardiness on the order of about 4-5 deg. F for a variety of cold sensitive plants, mostly palms, bananas and annuals. In some cases the protection was only a couple of degrees but in one case ranged up to 9 deg. F.

What’s the bottom line? For most gardeners the principle benefit of FreezePruf would be to protect plants from the first few early frosts in the fall. The question is whether you’d rather spray a relatively untested product versus relying on tried and true methods (e.g., bringing container planters in, covering sensitive plants with old bedsheets). The developers claim FreezePruf can last up to 6 weeks – that could save a lot of dragging bedsheets around the yard.

Caveats: FreezePruf is marketed as ‘Eco-Safe’ – whatever that means – although the MSDS sheets of some of the component products indicate eye and skin irritation are possible. Until a longer-term database is available I would be cautious of unintended results. For example, could this stuff make plants more attractive to pets or wildlife? We’ve seen reduced cold hardiness in conifers using WiltPruf alone, it would be interesting to see some data on Freeze-Pruf on conifers before recommending it for use on those.

Friday puzzle answer(s)

Wow! What a lot of great brainstorming over the weekend! I would venture to say that The Garden Professors have the smartest students in the world.

On to the answer…or answers. First, the phenomenon. It’s called paraheliotropism – literally, a movement to protect (the leaves) from the sun (yes, Trena, it is a tropism!). This is the opposite of another phenomenon called heliotropism, or solar tracking. Sunflowers famously do this, as do a number of arctic species that collect solar warmth for the benefit of their pollinators. (An aside: if you have never watched David Attenborough’s The Private Life of Plants you must add it to your Netflix queue. Right now.)

But our saxifrage (thanks, Holly! I’m such a taxonomy imbecile) is reducing solar exposure by positioning its leaves in parallel to the sun’s rays. This is a reversible movement and helps reduce photooxidative stress, leaf temperature, and water loss. It’s an important strategy as the newly emerging leaves are actively expanding. If turgor is reduced by high temperature or water loss, so is the final size of the leaf.

Finally, these rapidly expanding leaves have relatively thin cuticles (if they were thicker the leaves wouldn’t be able to expand as well). The cuticle gives further protection to the leaf from water loss due to heat, drought, wind, or even late season freezing events (thanks for that addition, John!). The cuticle will mature after the leaf has reached its full size.

So, as Foy suggested, this is a way for leaves to "harden off" and reach full size before exposing themselves to the sun. Aren’t plants cool?

And you are all such great participants! Group hug! Now, back to work.