Tulip Biology

The obvious reason for tulips to be interesting is their flower. Flowers are nature's advertising billboards. In nature it is always good if the genetic content of your species is mixed together as thoroughly and completely as possible (whatever the BNP, the KKK, and the other assorted idiots may think of the matter). Animals can actually move around to look for mates. Plants cannot, so must either produce copious amounts of pollen and disperse it by wind, or figure out a way to make sure things that can move around (like insects), pick it up and bring it to another flower. So they put nectar close to the pollen and the bees pick it up. Of course this introduces another problem. Bees have very clever eyes, but they're still only about 300x200 pixels, which is worse than even the earliest cell phone cameras.

So if you want to stand out in grass field, a green flower is probably a bad idea. That's why there's flowers of just about every color imaginable except green. Other colors which are common in nature are black (shadows), grey (rocks) and brown (earth, tree trunks). So those colors are best left alone. Pretty much everything else however is fair game.

A further twist: if flowers were all the same color, the incentive would be for other plants to 'copy' them to freeride. The flower could cease production of nectar, or water it down a lot, and the bees wouldn't be able to tell the difference, and would for this reason start paying less attention to flowers of that color. So what is needed is for a mechanism that ensures that the flower can change color, to diversify away from possible opposition. This is done through both genetic mutations, and genome recombination with other flowers. This last method in particular is exactly the reason the plant tries to attract bees in the first place!

The tulip makes a rather pretty flower, but that alone wouldn't have explained the tulip mania. The other element of the tulip's biology which we must understand are it's reproductive organs. The tulip has two ways of reproducing. The first is through the above mentioned seeds. The tulip produces about 200 each year, but they're useless, because since tulips cross-fertilize, they don't breed true: if you plant them, the resulting plant will be a mix of the tulip you collected the seed from, and some unknown tulip whose pollen managed to reach your precious flower.

What's worse this offspring is certain to express some genes that weren't active in any of the parents. These two things put together mean that any desirable mutations you managed to give to your flower are likely to be lost. Of course their important for the plant in the wild, because they are the only way the plant can recombine it's genome. But as far as we're concerned, we can forget about tulip seeds, they're irrelevant for the purpose of breading desireable varieties.

The second way tulips have of reproducing is through their bulb. The bulb looks like an onion. In fact it is an onion, or better still, what we call onion in the kitchen is actually just the bulb of the onion plant. A bulb is simply a way to store energy. It's one of several mechanism that plants have developed to allow them to survive in places that have suitable growing seasons, but that also regularly feature extended periods of adverse conditions, such as extremely cold winters.
If the plant had to start all over again from a seed, it would at first be able to grow only very slowly, since it would have to first produce the energy to grow leaves, and then use the leaves to grow the flower, fruit and seeds. This means that if the growing season is short, much of it will be wasted by the early growth phase, and if the season happens to be shorter than usual, the plant may not successfully bring a fruit (with its precious seeds) to maturation, and the plant could then die in the winter without leaving any progeny. A single bad year could virtually wipe out an entire population. Think of it as a small firm that has no access to the credit market, and can thus only grow from reinvesting it's profits.

Plants living in harsh climates avoid this problem by each year storing as much energy as possible in the bulb, an underground structure which evolved from leaves. Afterwards, the plant just lets the outside of the plant die, and the next spring it can push up a new stem from these roots. Of course since it has such a large reserve of stored energy in the bulb from last year, the leaves will take far less to grow. Even better, since the energy for this growth doesn't have to come from photosynthesis, the plant can start the whole process earlier than it otherwise would have to. By the time the sun does come around, the plant can already have it's leaves deployed, ready to draw every last glimpses of sun possible. As this happens, the bulb shrinks as it's energy is depleted. But as soon as the leaves develop you can start using the energy to produce a flower and then start accumulating energy in the roots again, so the cycle can repeat.

So this ability to 'save' by using the bulb to store energy helps the plant in many ways

• it allows it to have the leaves already deployed when the sun comes, this maximizes total energy production

• it allows it to potentially bloom earlier, allowing it to be one of few food sources for pollinators early in the growth season, allowing it to receive a disproportionate amount of attention. This would maximize pollen dissemination, allowing it to disseminate evolutionarily beneficial adaptations across the population faster
  

• it allows it to survive lean years: even if the growing season was so short that the above wasn't enough and the plant never bore fruit, what little energy had indeed accumulated in the bulb would have probably allowed it to survive until next year, 'in hopes' of a longer growth season.

• it also allows it to reproduce by clonation on virtually all years in which the plant survives: when the plant starts forming the new bulb during the growth phase, the plant actually creates several. Each one of these bulbs will push up a separate plant in the next spring.
  

There are two problems with storing energy. The first one is that in general, it is costly. In the plant world, savings don't generate interest. Far from it, it actually costs to the plant to invest in energy storage by growing cells that produce and store the starches or sugars they use as reserves. This process is fairly inefficient. The reverse conversion each spring, when the plant extracts it's energy from the bulb, is also inefficient.
So the plant must have a strong reason to invest into this. Of course the reason is the exceptionally harsh winter conditions requiring a new plant to be grown each year, and the variability in the length of the season placing a premium on the plants ability to survive to try again the next year.

The other problem is that the plants aren't the only living things capable of using starches and sugars for energy. Animals are going to eventually learn that it's a good idea to eat them. This is why they stored the energy underground to begin with: out of sight. But in no time (a few million years) animals are going to evolve all sorts of specialised senses and techniques to find them. So most plants that use this strategy also have defence mechanisms. Potatoes (which use a different take on the same idea) contain neuro-toxins, though the domesticated varieties we eat are selected to be safe.
Both garlic and onions have specialized structures that keep two different substances separated. When these two substances mix (as happens when somebody brakes the barriers in between these structures by biting them), they release a gas called syn-propanethial-S-oxide. This eventually reaches your eye and combines with water in your tears to produce a dilute form of sulphuric acid.
When humans develop something like this, it is called a binary chemical weapon. Don't tell Bush about this or nobody living within a 100km radius from an onion field will be safe from stray bombs. Like all WMD programs, this one is also fairly expensive. The cost of building up these defences to defend the 'savings' must be added to the cost of maintaining a storage system.

As an aside, please reflect on the differing importance that different animals, if queried, would assign to the different parts of the plant.

As we shall see, this distinction between agents whose primary interest lies in the bulb, and agents for whom it lies in the flower, is a feature that crosses over from the animal 'market' to the human one.

Now, back to the biology. Here comes the important part. The cells in the bulb never combine with genetic material from other tulips. Year after year, you can expect the same bulb to push up a flower looking more or less like the one of the year before. So if you plant 200,000 tulip seeds, and one of them comes up pink with yellow stripes, the only way you can get a flower like that next year, is by keeping that bulb handy. Remember: the seeds are completely unreliable.
And now here comes the REALLY important part: as we've noted earlier, after producing their pretty flower, the tulip doesn't just create one bulb like an onion does, it produces several, in a similar way to how garlic has distinct cloves. Each of those bulbs can push up a new tulip, and each of those tulips is a genetic clone of it's parent, so is expected to look just like it!
This is great news. So when that pink-with-yellow-stripes tulip withers in the fall, you can dig up the bulbs, and each one of those can in the spring produce a tulip, which will be pink-with-yellow-stripes, and which will by the fall have produced five or so more bulbs, and so on.

So let's just stop here for a second, and just think about what we have.
We have a plant, which produces something which has value (the flower). The only way to get that flower, is through possession of a suitable bulb. If you plant a bulb, you can hope to have several more bulbs in the fall, which you can re-plant or sell. If you've developed a new colour of tulip, nobody can have a tulip like yours, unless they buy one of your bulbs.
So not only is a tulip a consumer good, it is also an investment good used for producing itself!

This feature of it's reproduction is the key element of the market for tulips. Like in icebergs, the flashy part is on top, but what really matters is in the bottom.

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