Weed of the week - ragweed

Your eyes may have just started to water just looking at these images of giant ragweed. The plants can reach 7-8 feet tall easy and a local walking/bicycling trail goes through a virtual gully of them just now coming into bloom. There are so many flowers they'll leave a yellow dusting of haploid males (pollen) on the ground.  Woe be to any allergic people who hazard this gauntlet.  Both the common and giant ragweeds are easy enough to recognize, but they are usually ignored in the spring when they are more easily controlled by mowing them down or whacking them out, or by herbicide application in the spring or early summer.  Too late now.  The smaller common ragweed showed up in an older blog and you will notice the highly lobed leaves that Linnaeus thought resembled wormwood, thus Ambrosia artemisiifolia.  Notice that the giant ragweed has three lobed leaves Ambrosia trifida (shown above) and the flowers are not showy at all because it's wind pollinated, so the co-flowering goldenrod gets the blame for hayfever. The flowers shown are just prior to flowering.  How long can you hold your breath?  

What is pollen?

Dear Phytophactor, Apart from you blog the best description I can find is that pollen is essentially a "detachable plant penis".  But you refer to pollen as a "male organisms". So is "detachable plant penis a reasonable description, or is that lending itself to another misconception?  An interested reader.

Dear Reader, Trust your Phytophactor to get such things correct.  Pollen is a whole male organism, sex organ included (which it really doesn't have), although a pollen tube delivers the sperm.

Dear Phytophactor,  Thanks, but if I can ask another question.  My confusion stems from the my not understanding if pollen is a male organism, how does that work?  So does a male organism produce tons of tiny male organisms?  I'm guessing that the real problem is the desire to fully equate plant and animal reproduction, but I'm struggling to understand a male producing lots of males to reproduce.

Dear Reader, Bingo, you can't equate the plant sexual life cycle to that of animals.  The plant life cycle evolved to solve the problem of living on land.  Swimming sperm could no longer disperse to find an egg to fertilize, so plants make tiny disposable males (pollen, which is really a spore prior to development.)  So equating plants to animals is the real problem, but people did do that although it came our totally wrong, flowers don't have ovaries (the units thereof are modified leaves bearing sporangia, carpels), and those sporangia, while eggish looking, are not ovules but sporangia that produce one big spore that develops into a female who produces an egg.  The anthers are also modified leaves bearing sporangia that produce lots of small spores that become pollen.
Hope that helps; look up a fern life cycle and then imagine the haploid gametophyte (a sexual organism) as being either male or female (as in seed plants & there are a couple of other differences too).  You might want to get a copy of "How the Earth turned green" from Chicago University Press. This book spends a lot of time explaining this.  You might also check out my blog on seeds.

This is the kind of question TPP tends to get, plant misconception piled on top of plant misconception. But kindly TPP did not name the reader.

Squash pollination & fruiting

The F1 has a huge zucchini plant, but yet she reports not many fruit; "They're little and fall off." Ah, a pollination problem, right up TPP's alley.  Garden squash plants are what we call monoecious, one house; they produce two kinds of flowers on the same plant, those producing pollen ("males") and those producing fruit and seed ("female").  They aren't actually male and female, but the explanation takes more effort that TPP has right now.  The plants usually start out producing male flowers, they use less energy to make so plants can start flowering at a smaller size.  The female flowers are easy to distinguish because you can see the immature fruit below the yellow corolla (right side), which is lacking on the males (left). If not pollinated, no more energy is wasted and the flower aborts. This can happen in a small garden, maybe with only 1 zucchini plant because maybe no males flowers were produced on a particular day. However it also could be because you don't have any bees around to move the pollen for you (or you have left a row cover in place too long keeping the pollinating insects our along with the bad guys). If you lack bees you can pick a male flower, tear off the yellow corolla, and swab the anthers on the stigma of one or more female flowers effecting pollination yourself. This can also happen with cucumbers. Bees visit male flowers and collect pollen as a reward; females flowers have stigmas that mimics the males, thus deceiving pollinators into visiting and delivering pollen.  Tricksy plants! Note the flowers are edible themselves, so if you are getting too many squash, try eating some at their smallest stage.
For more information on raising squash and their relatives go to Renee's Garden.  The image used above is from this site.

No, no, no, no, no - Goldenrod doesn't cause hayfever!

The fall allergy season is here, almost. The harvest season kicks up lots of dust and mold spores, and ragweed comes into flower soon. The local newspaper had a nice sidebar article about allergies and they mentioned all of these factors, BUT then some moron put a picture of goldenrod in bloom above the article! Now maybe they think goldenrod is ragweed, or that goldenrod causes allergies; wrong and wrong. Here's the problem: they both flower at about the same time, and most people see and recognize goldenrod, but they don't see or recognize ragweed. This is because goldenrod is insect pollinated; you should know this because the flowers are showy to attract pollinators. Ragweed flowers are green and seldom noticed as a result, but the plant is wind-pollinated so it must make a lot of pollen to blow around. Once again, TPP only wishes they would check with their friendly neighborhood botanist before doing such things; he doesn't charge much.

Pollen is not plant sperm

Anything plant related, no matter how crazy, gets directed to TPP.  So it was that TPP finds himself being interviewed about seasonal allergies. Right? Actually having talked to a bunch of allergists, the writer found themselves wondering about pollen, so she gets sent to someone who knows a little bit about how pollen works from the floral perspective.  OK, so I know pollen is plant sperm, but why does it irritate your nose?  First, pollen is not plant sperm, it's a whole, albeit microscopically small, male organism, and like all males, it produces sperm after pollination takes place.  What?  It's a male? Then where is the female?  Hmm, this lady is quicker than most of my students who never think to ask that question.  She's there, residing inside each and every ovule, which is not an egg, housed within an ovary, which is not a sex organ.  Those traditional names are a testament to the same misconception about plant sex that you started with.  Pollen isn't sperm; and a plant ovule isn't an egg.  TPP wonders how many times he's explained this during his career and seemingly with no impact what so ever except perhaps on a case by case basis. Misconceptions about plants have more lives, and much longer lives, than a cat.  The true nature of the seed plant life cycle has been understood since Wilhelm Hofmeister published his magnum opus on plant evolution in 1851.  So that's only been a mere 162 years, and still a jacketed megasporangium is called an ovule (although TPP does admit the convenience of the term, which botanists still use while knowing it implies pure wrong thinking).  However, at the end of my lesson, my interviewer said, "Oh, you're good! You explain things so well."  Thank you, and it only took 43 years of practice.

Good year for haploid males

Enough about the weather, but since it is late summer, we must post on a topic TPP has visited before. This will be no surprise for people who suffer from hayfever, but this has been a very good year for haploid males, not all haploid males, but certainly those being dispersed by common species of Ambrosia (ragweed).  The giant ragweed around here, and in one location it borders a jogging/walking/bicycling trail so thickly it's a wonder anyone can survive this pollen gauntlet, has done very well in spite of the drought.  So for all you hayfever sufferers, it's looking like a bad season as the ragweed begins to flower and disperse it's tiny wind-dispersed males (pollen).  Of course, many people here abouts blame goldenrods for their hayfever because they flower at about the same time as ragweed and having colorful flowers, they are noticed.  However, colorful displays means they are attracting insects to disperse their pollen, and it isn't blowing around on the wind to be inhaled.  The only thing that still puzzles TPP, and the answer has eluded me for years, is why were ragweeds named after ambrosia, something delightful to taste and smell, unless this was Linnaeus' idea of a joke. 

Hay fever - It's ragweed, not goldenrod

At least once every late summer/fall season, TPP has to explain that it's ragweed that aggrevates your allergies, not goldenrod.  Funny though, don't think it ever was in one of my blogs.  Wonder why?  No matter, the Annotated Flora has done a very nice job of explaining about this complete with pictures, but probably, someone will still ask.  The general rule is simple: if something is gaudy enough for you to notice the flowers, then it isn't engaging in wind pollination and the pollen isn't getting into your nose.  The same problem occurs in the spring because some people are allergic to pollen from trees with inconspicuous flowers and they bloom at the same time as black locust trees.  But those big masses of white flowers are to attract insect pollinators, so unless a bee flies up your nose, black locust pollen isn't causing your hay fever.

Are you allergic to haploid males?

Smarting, itching, watery eyes? Well, you could be allergic to males, not human males, who are more likely to just be annoying, but those endosporic haploid males wafting about and hoping to land upon a receptive stigma but end up in your nasal passages instead, those plant male gametophytes better known as pollen. Aided and abetted by the warm, dry weather, this fall’s allergy season is in full gear. Ragweed pollen is at an all time high in the upper Midwest this year, and then you get to add in harvest dust with all its mold spores for an allergy aggravating cocktail. It's a wonder the Phactor can breath at all.

Tree clones: immortality and sex

The oldest organisms on Earth are clonal organisms. Plants seem to have the capacity for immortality because they have perpetually juvenile tissues (meristems) capable of continued growth, and further, certain plant cells can dedifferentiate, return to a juvenile state, for wound repair and growth. This capacity is widely used in the vegetative reproduction of economically important plants. But can a clone live forever? Probably not, but they can be very old. The Pando clone of quaking aspen in Utah is estimated to be at least 80,000 years old, and some estimates place its age as 10 times older, which would make this clone as old as our whole species! Not only is Pando impressively old, it’s big covering over 40 hectares and at over 6000 tons is the largest organism alive. Now of course one problem with being an immobile species is that the longer you live the more likely you’ll encounter some environmental disaster, a fire, a flood, a volcanic eruption, a storm, a chain saw. But clones have a sex problem. Since they are all one genetic individual although looking like a whole forest, they cannot produce seed except by exchanging pollen with another individual, and when one individual occupies the whole area that becomes less likely. Even worse recent research suggests that as the clone gets older, it loses sexual vitality because of an accumulation of mutations. These show up in pollen because pollen only has one copy of each gene so if a harmful mutation occurs it may affect the viability of the pollen, a harm that does not affect the tree because in its tissues chromosomes and genes occur in pairs. By the relatively young age of 20,000 fertility can be diminished by more than 3/4s. So the clone may live a long time, but as it ages, its ability to sire offspring and start a new individual drops, but who knows Pando may already have lots of offspring.

Have you thanked a bumblebee today?

Land plants had a problem; they inherited swimming sperm from their algal ancestors, but they no longer lived in an aquatic environment. Flowering plants, the most recent group of land plants to appear, have solved the “swimming sperm” problem by having evolved miniaturized haploid males that do the dispersing over distances far too great for any sperm to swim. These tiny male organisms are called pollen, and unlike most other land plants who used wind or water to disperse their spores, over 80% of flowering plants use biotic dispersers – animals who are rewarded or seduced or deceived into acting as pollen vectors. Over 200,000 insect species act as pollinators – mostly bees, butterflies, moths, beetles, and flies. About 1000 species of birds and mammals (mostly bats) also function as pollinators. This biotic interaction is quite important to our species because quite a large number of the plants that we depend upon require pollinators to reproduce, and in the case of fruit and seed crops, to produce what we want. So this week is set aside to celebrate pollination. Woo, hoo! Here beetles and butterflies participate in the pollination of wild carrot. Such wild pollinators provide billions of dollars of serve to us, yet too often they are taken for granted and our activities may be reducing many of their populations.

What is a seed?

Seeds are perhaps the most misunderstood and misinterpreted of botanical subjects. You plant a radish seed, a radish grows, flowers, gets pollinated, fruits, and the seeds within contain an embryonic radish plant. This seems simple enough, rather like chickens. In fact the traditional name for an immature seed at the time of pollination is an ovule, literally an egg. So of course the floral structure that houses ovules must be an ovary. Oh so very like an animal, NOT!

An ovule is actually a sporangium, a jacketed, unopening sporangium that produces 1 spore via meiosis thus reducing the chromosome number from diploid to haploid. The spore develops into a female organism, a gametophyte, that ultimately produces a real egg. Pollen is also a spore at its inception, and it too develops into a haploid male organism, albeit a very tiny and reduced fellow. Having a small dispersible male solves the swimming-sperm problem that land plants with free-living gametophytes have, e.g., ferns.

Pollination is the completion of the male’s dispersal trip. A pollen tube that grows from him to her delivers the sperm, fertilizes the egg, and results in a new embryo. When the entire kit and caboodle is mature, the jacketed sporangium, what’s left of the female, and the resulting embryo of a new diploid plant (a sporophyte) gets dispersed as a seed.

The seed plant life cycle only makes sense as an evolutionary solution to a reproductive problem that limited the distribution of land plants.

Here are some great false color images of seeds and pollen complements of the Royal Botanical Garden at Kew. HT to DD at Neuron Culture.