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!
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.
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 |
|
|
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.
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.
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.
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.
Spring is coming…and soon herbaceous perennials will poking their leaves up through the mulch:
Obviously as leaves first emerge they’ll be vertically oriented – but these ones have remained vertical days after emerging. Eventually they’ll become horizontal. But today’s question is – what’s the advantage in remaining vertical? And what’s this phenomenon called?
Answer on Monday – have a nice weekend!
Some odds and ends today that I either #1 was asked to post or #2 couldn’t resist posting. First for the picture that I was asked to post.
This, as far as we can tell (we being myself, my technician, and our grounds department), is the American elm tree that was being planted in that picture from 1909 which I posted on January 21. Dutch elm disease was devastating here in the mid 1900s as it was everywhere, but this region of the world was lucky and there were a number of escapes — and resistant trees (that’s an ongoing project of mine — working with DED resistant elms — I’ll probably post more about it this spring). Anyway, the tree is a little smaller than I would normally expect for an elm of this age, but the proximity of the road and sidewalk could easily have stunted its growth.
Now for the stuff that I can’t resist posting — mostly having to do with Bert’s post on January 25. Chad (my technician — if you follow the blog you’ll remember him, 6’4″ — etc.) was showing me a book titled Shade-Trees in Towns and Cites by William Solotaroff published in 1911 and it had this great shot of filling a tree cavity. So here it is:
The book also had a great shot of what they did to a trees canopy before they planted:
This type of pruning isn’t necessary at all. When trees are planted they adapt to the amount of roots which they have by producing fewer, or smaller leaves.
Update:
Here is a photo of the leaves of a freeman maple which was severely rootpruned right before planting and, below it, the leaves of a similar maple whose roots were left pretty much intact (both plants were container grown).
As you can see, trees have their own methods of dealing with root loss — no need for us to come in and clip their tops off. Now, two years later, both of these trees (and all of the others in the research plot) look pretty much identical.
In the wake of The Garden Professors’ sudden notoriety (see Linda’s Jan. 26 post), my department head sent out a very kind e-mail announcement to our faculty, staff, and grad students.
However, he referred to us as the "Hort Professors" blog, sans hyperlink.
A curious staff member (the lovely and talented Pris Sears) searched that title, resulting in the following:
Hort Professors, Hot Professors…kind of the same thing. Thanks, Google!
I haven’t finished with the water droplets story yet – but I just had to add some more evidence to the tree planting discussion from last week.
Consider this series of photos below. This is a street tree in Kennewick, WA (in the southeastern part of the state, where summers can be intensely hot and dry). Every spring, this tree leafs out just fine – and every summer the leaves suffer marginal and tip scorch. This is a classic symptom of chronic drought:
As an amenity, the tree fails. Even though the landscape is well-watered, as shown by the healthy turf in the next photo, the canopy is sparse and dry.
An excavation of the roots explains why: the tree was planted too deeply and has developed a secondary set of roots:
Note how sparse these roots are – which is typical of many adventitious root systems. While the roots are adequate for water uptake during the cool spring weather, the hot dry summers suck away more water from the leaves than this puny root system can absorb, even when well-watered.
My point: sure, trees might survive being planted too deeply. But thrive? Not in this case – and this is a well-managed landscape! With less care this tree would have died long ago. The only solution here would be to replace this tree – correctly.