Competing sinks?

Just because two plants are sufficiently closely related to graft them together doesn't necessarily mean it's a good idea to graft them together.

I must confess that, beyond the novelty value, I don't quite get the amazing tomato-potato.

It seems more sensible from a plant physiology point of view to just plant a tomato next to a potato and have two sets of leaves each providing for one sink rather than have two large sinks competing for the same resources. I initially wondered if maybe the potatoes ripened first and then maybe the tomatoes but the inset photograph seems to show them both ripe together.

Given that tobacco is also in the Solanaceae family I wonder how long it will be before we see tomacco for real? Oh wait someone already did that.

Angel's trumpet poisoning

I looked up some information on the toxic compounds in Brugmansia. The plant contains an unhealthy brew of the alkaloids atropine, scopolamine and hyoscyamine.

Because these can cause hallucinogenic effects they are often ingested by those seeking just such an effect. When combined with alcohol the effects can be rapid. Although the plant can be eaten or smoked the most popular method of ingestion is to prepare a tea from the flowers and seeds.

Unfortunately because the levels of the alkaloids vary widely from season to season it is very easy to overdose and it is estimated that 'teas prepared from as few as 10 flowers could be extremely toxic if not fatal'. Angel's trumpet ingestion produces the classic symptoms of anticholinergic poisoning, so classic that they have their own mnemonic: 'hot as a hare, dry as a bone, blind as a bat, red as a beet and mad as a hatter.'

This paper, Ingestion of Angel's Trumpet: An increasingly Common Source of Toxicity, reports a ten fold increase in Brugmanisa poisoning in Florida in 1994. They failed to locate a particular reason for this (ie reference to Brugmania use in a movie) and suggest the idea was simply spread by word of mouth. And then the internet came along...

The Birds and the Bees and the Flowers and the Trees

Given that about 5% of angiosperms are dioecious but only a few cases of sex chromosomes have been discovered this raises the question of how sex is determined in the rest of these species. I found this nice review in the journal Genetics last year:
The Birds and the Bees and the Flowers and the Trees: Lessons from Genetic Mapping of Sex Determination in Plants and Animals

Sex determination is an important area of study in developmental and evolutionary biology, as well as ecology. Its importance for organisms might suggest that sex determination is highly conserved. However, genetic studies have shown that sex determination mechanisms, and the genes involved, are surprisingly labile.

Trees, photosynthesis and weasels

Any questions?

The Evolution of Sex Chromosomes

Sex chromosomes have arisen independently in many taxonomic groups. It is an interesting question whether the same mechanisms were involved each time.

Sex chromosomes are an oddity in flowering plants. They are limited to dioecious species and only a few examples are known. The genus Silene, which includes the White Campion, includes both dioecious and hermaphrodite species and three of the dioecious species, Silene dioica, S. latifolia, and S. diclinis,  have an X-Y sex-determination system where Y specifies maleness.
Although the X-Y system evolved quite recently in Silene (less than 10 million years ago) compared to mammals (about 320 million years ago), our results suggest that similar processes have been at work in the evolution of sex chromosomes in plants and mammals, and shed some light on the molecular mechanisms suppressing recombination between X and Y chromosomes.

Ref:  Nicolas M, Marais G, Hykelova V, Janousek B, Laporte V, et al. (2005) A Gradual Process of Recombination Restriction in the Evolutionary History of the Sex Chromosomes in Dioecious Plants. PLoS Biol 3(1).

There's a synopsis of the article in the same issue: Evolution of Sex Chromosomes: The Case of the White Campion.

The plant in you (and vice versa)

 From: Double-fertilization, from myths to reality, a review from 2007 -

It is becoming gradually clear that although plant and animal kingdoms diverged more than 1 billion years ago, similar mechanisms govern sexual reproduction in both kingdoms. The review by Márton and Dresselhaus (2008) outlines some of these parallels. The current idiosyncratic nomenclature used to designate plant reproduction has obscured the parallels that now become apparent between plants and animals. It is likely to be the time to rethink the designation of each actor of the reproductive process such that the literature in the field becomes relevant to a broader readership working in the field of reproductive biology.
The  Márton and Dresselhauspaper referred to is A comparison of early molecular fertilization mechanisms in animals and flowering plants.

Why did the tumbleweed cross the road?

Apart from the cool galloping mosses below one of the few examples of a mobile adult plant is the tumbleweed. A number of plants in dry and windy environments have evolved a similar strategy of disengaging from their roots when mature and then, although the mature plant is dead, using the large tumbling plant body as a mechanism of seed dispersal. Seeds may be dispersed as the plant tumbles along or in other species it actually requires the presence of moisture to cause the seed pods to open and release the seeds.

NASA have even used the tumbleweed as inspiration for a low cost (well, relatively low cost, it IS NASA) Mars Rover.

Transpirational Pull

Maria-Cristina linked to David Attenborough's Private Life of Plants series below but I thought I'd add this clip about plant water transport. He makes an obvious point that I'd never thought of before - plants move all this water silently! I also realize that like David Attenborough I forgot to point out that this entire process ('pulling' up very long thin tubes of water) only works because of the extraordinary properties of water - in this case its hydrogen bonding which gives the tube of water great strength.

Sex crazed suitors and more moth

Proboscis prediction

I mentioned the Madagascar Star Orchid, aka Star of Bethlehem orchid, comet orchid and Darwin's orchid when we talked about evolution.

Based on the extremely long corolla (about a foot in length) the moths would need to probe to get the nectar Darwin deduced that there must be moths with extremely long tongues in Madagascar even though he never saw them:

"It is, however, surprising that any insect should be able to reach the nectar: our English sphinxes have probosces as long as their bodies: but in Madagascar there must be moths with probosces capable of extension to a length of between ten and eleven inches!" Darwin, 1862 in On the various contrivances by which British and foreign orchids are fertilised by insects, and on the good effects of intercrossing.

This photo was the Botany Photo of the day on Feb 12th and they include a link to an interesting paper in the American Entomologist entitled Darwin's Madagascan Hawk Moth Prediction that describes how Darwin's description of the orchid and proposed moth was ridiculed by some as being impossible while others suggested the long nectaries were proof of supernatural creation. Darwin and Wallace went on to explain how evolutionary processes could develop both a long-nectaried orchid species and a co-evolved moth.

Unfortunately Darwin did not live long enough to see the discovery of the moth in 1903. Although the moth was originally named "praedicta" in honor of the fact that Darwin predicted its existence the name was later, unfortunately, changed.

The moth approaches the flower to ascertain by scent whether or not it is the correct orchid species. Then the moth backs up over a foot and unrolls its proboscis, then flies forward, inserting it into the orchid's spur.

Inorganic Flora

Check out Macuto Murayama's flower illustrations. Apparently he spends months on each one by dissecting out all the floral parts, sketching and photographing them, then renders them in 3-D software before recompositing the image in photoshop. The resultant image have a ghostly x-ray quality to them combined with the precision of a scientific illustration and yet have a great artistic beauty. Lots more examples at the link and there are more details on the artist and his technique here.

It is not only an image of a plant, but representation of the intellect’s power and its elaborate tools for scrutinizing nature. The transparency of this work refers not only to the lucid petals of a flower, but to the ambitious, romantic and utopian struggle of science to see and present the world as transparent (completely seen, entirely grasped) object.

Herbal supplements

Sometimes there is too much information on the internet and sorting out the crazy from the really crazy is tricky. Fortunately when it comes to health and nutrition the government itself actually has some pretty good websites and information. You are probably familiar with the NIH and CDC websites but the Nutrition.gov website is pretty good too and is a good source for information on botanical and herbal supplements and medicines Nutrition.gov is produced by the National Agricultural Library, part of USDA.

You can read more about gymnosperm derived compounds such as Ephedra and Ginkgo and numerous other herbal supplements and remedies.

You can download all the factsheets at once in pdf format if you click the image above. If you know someone who is a little too into herbal remedies you may want to pass on a copy. Not because the herbs are necessarily bad or dangerous but because they may have adverse interactions with other commonly prescribed medicines (eg for diabetes or blood pressure) and the factsheets clearly summarize our current state of knowledge.

Gymnosperm Reproduction Videos

I just watched these again and they really are pretty good. This is, of course, WAY more information than we covered in class but it really helps a lot to see some of this happen in clear 3-d diagrams. The first one is very short and a little obvious but I liked the second and third ones a lot. I thought they really helped in visualizing what is going on.

It's all one song

"It's all one song." -- Neil Young replying to a man in the audience, who said "It all sounds the same!"
I just discovered WikiQuote and it's there so it must be true.

Anywhow I'm probably the only person who thinks this is a good metaphor for evolution, particularly macroevolution, but this story made me think of it again.

In a finding that overturns conventional wisdom, scientists are reporting the first discovery of the female sex hormone progesterone in a plant. Until now, scientists thought that only animals could make progesterone.

"While the biological role of progesterone has been extensively studied in mammals, the reason for its presence in plants is less apparent." They speculate that the hormone, like other steroid hormones, might be an ancient bioregulator that evolved billions of years ago, before the appearance of modern plants and animals.

It seems to me we shouldn't be too surprised by the discovery of progesterone in plants because it is, after all, all one song.

Occurrence of Progesterone and Related Animal Steroids in Two Higher Plants

J. Nat. Prod., January 28, 2010

Stomatal defense/defence

Don't forget that this blog ran last year. There are all sorts of juicy postings lurking down there. You can select by topic or just browse. For example I was just looking what I'd posted on Plant Physiology last year (to prevent repetition) when I remembered this posting and decided it WAS worthy of repetition because it ties together so many different parts of this course, ecology evolution and physiology.

How do the various processes that affect stomatal opening and closure coordinate their actions? What happens if the stomata get conflicting signals?

I just started to do some reading on this when I came across this amazing paper from 2006 describing how stomata close upon detection of potential microbial pathogens to prevent the infection of the leaf interior. That's pretty cool but they also show how pathogenic bacteria have evolved strategies to suppress the closure of stomata! This appears to be brand new research and I think it is both the first demonstration of the defensive role of stomata as well as the first demonstration of bacteria overcoming this defense.

The journal editors obviously thought was pretty cool too since there's a nice preview of the research.

Plant Stomata Function in Innate Immunity against Bacterial Invasion
Cell, Volume 126, Issue 5, 8 September 2006, Pages 969-980
Maeli Melotto, William Underwood, Jessica Koczan, Kinya Nomura and Sheng Yang He

Florigen - found and not found

From Science magazine's list of the 'Breakthrough's of the year' in 2005:

In August three groups of plant molecular biologists finally pinned down the identity of florigen, a signal that initiates the seasonal development of flowers. The signal is the messenger RNA of a gene called FT. When days get long enough, this RNA moves from leaves to the growth tip, where the FT protein interacts with a growth tip-specific transcription factor, FD.

However if you click on the original article then you may notice the sentence 'This article has been retracted.'

After the first author (T.H.) left the Umeå Plant Science Centre for another position, analysis of his original data revealed several anomalies. It is apparent from these files that data from the real-time RT-PCR were analyzed incorrectly. Certain data points were removed, while other data points were given increased weight in the statistical analysis. When all the primary real-time RT-PCR data are subjected to correct statistical analysis, most of the reported significant differences between time points disappear. Because of this, we are retracting the paper in its entirety.

In new experiments, we have reproduced the floral induction caused by a heat-shock induction of FT in a single leaf, but we have failed to detect movement of the transgenic FT mRNA from leaf to shoot apex. We therefore retract the conclusion that FT mRNA is part of the floral inductive signal moving from leaf to shoot apex.

Curious. After 70 years of elusivity (is that a word?) Florigen is not ready to give in yet.

Where did all that stuff come from?

Just about everyone will agree that trees are made from sunlight, water, and soil the trees sucks up from their roots. But the surprising truth is that trees are made from air! Trees are solar-powered machines that convert air into wood. Why is it that, despite the fact that photosynthesis is one of the most widely taught subjects in science, so few people really understand the central idea underlying this system?

Watch the video here.

I think this is more of a commentary on teaching than it is a criticism of these students, or students in general.

RedDetect

As I mentioned today the global landmine problem is getting worse, not better. Currently landmines are being planted at a rate 25x greater than they are being cleared. According to the UN, even if no more landmines were planted ever again it would take over 1100 years to remove all the mines that are currently in place using present day technology.

Although innovative programs like the HeroRats organization can greatly speed up demining, there is a clear need for multiple tools to manage the growing problem. The Nitrogen dioxide detecting plants, RedDetect, I mentioned in class are now being developed by Aresa - a non-profit organization in Wallonia, a part of Belgium. Although Arabidopsis plants were originally used it was decided that, although they grow quickly, they were not visible enough from a distance (kind of important if you want to stand well back). Therefore the same technqiue has been applied to tobacco plants. The tobacco plant was chosen as it is known to grow well in a wide range of environmental conditions and any changes in colour can easily be seen because of its large leaves. The tobacco plants were transformed in the same way as the Arabidopsis with an activation gene from the snapdragon plant, which enables them to detect nitrogen dioxide, a by-product of landmines, in contaminated soil. This releases anthocyanin, a natural red plant pigment, into the leaves.

As of April 2009 the plants have already been successfully tested in laboratories and greenhouses and are now undergoing field trials in Serbia and South Africa. The plants only detect the mines of course, someone still needs to physically remove them...

One of the guys that took us into the minefield has stepped on 6 landmines. The first landmine blew off his foot. The next landmine took off half his leg. The next 4 blew his prosthetic leg to pieces, and he hopped down to the NGO for a replacement. Yet, he keeps going back into the minefields to illegally cut down trees that he can sell to the Thais for $5 a piece. This is how he feeds his family. And that is the life of a village de-miner.
From Adam Katz's blog entry about a visit to a Cambodian minefield.

Double fertilization – caught in the act

There was an article in Trends in Plant Science last year called Double fertilization – caught in the act that both reviews the field and includes photographs of Arabidopsis plants caught in the act....

In flowering plants, fertilization is unique because it involves two pairs of male and female gametes, a process known as double fertilization. Here, we provide an overview of the field and a detailed review of the outstanding recent advances, including in vivo imaging of double fertilization and the identification of a signaling pathway controlling the release of the male gametes and of a protein involved in gamete membrane fusion. These recent results are stepping stones for further research; our knowledge of double fertilization is expanding as newly discovered molecular pathways are explored and new mutants are characterized. Controlling plant fertilization is essential for seed production, and molecular understanding of double fertilization will provide the tools to improve crops and breeding programs.

How plants make decisions

In the early edition of PNAS this week is Ecological modulation of plant defense via phytochrome control of jasmonate sensitivity.

This paper describes how plants balance the tradeoff between growth and defence. The same light sensor that detects other plants crowding in and gives the signal to switch on the synthesis of the plant growth hormone auxin reduces the plant's responsiveness to the hormone jasmonic acid, which orchestrates the synthesis of a whole array of defensive chemicals.

Coupling shade avoidance syndrome with the regulation of resource allocation to defense could provide a major selective advantage for plants growing in the wild, but might increase the vulnerability of densely planted crops to insects.

Hmm. I guess this is more relevant to next quarter but I thought it was an interesting paper. Here are a couple of past posts of more relevance to our current topics:

• Hox
• Woof