A. Techniques for breeding unusual varieties of tulips in the Netherlands
B. New types of plants introduced to Europe through trade
C. The spread of plant diseases throughout seventeenth-century Europe
D. The impact of a plant virus in the Netherlands in the seventeenth century
NARRATOR:Listen to part of a lecture in a botany class.
FEMALE PROFESSOR:OK, let's move on... to bacteria and viruses that can infect plants.And let's start out with a virus that's rather common in various plants, but first became known in connection with tulips.This virus can cause a change in pigmentation that dramatically affects the color of the plant's leaves or flower petals.But since not all cells of the plant tissue are infected, the result tends to be color variation... with color intensified in one part of the flower petal and faded in another. This is called color breaking.And the virus that causes this in tulips is called the tulip breaking virus.
The tulip breaking virus is now known to have detrimental effects on plants- they're weaker and sometimes reduced in size.But for centuries, people didn't have a clue about this virus.Not until the early 1900s was it known what caused the color breaking in tulips- what made the tulip plant produce flower petals so radically different, in color or in pattern, from what you would've expected.Tulip flowers with stripes or streaks, or feather or flame patterns on their petals- there's no doubt in my mind that these symptoms of this breaking virus affected human behavior too, indirectly- that they set off the famous tulip craze in the Netherlands. Let me explain.
In the seventeenth century, the Netherlands was among the most important trading centers in all of Europe... with lots of rich merchants who wanted to showcase their wealth... for example, by displaying exotic tulips in their private gardens.Now, tulips are not native to the Netherlands. They originated in the mountains of central Asia and spread from Persia, present-day Iran, to the Turkish Ottoman Empire, and from there, eventually reached Europe.There's an explanation for the origin of the name "tulip" that kinda reflects this: apparently, it came from a Persian word for "turban"... you know, a cloth wound around the head... um, a style of headgear worn by men in that part of the world.Well, the Ottomans used a similar name for tulips after they acquired them from Persia.And then, in the late sixteenth century, a variation on that name found its way from what is now Turkey...to the Netherlands... along with the plant itself.
OK. A tulip, of course, is typically grown from an underground bulb.And although, as it flowers, the old bulb shrivels to almost nothing, the plant produces another large bulb-and maybe two, three, four smaller ones-to take its place.And while tulips take up to seven years to bloom if you start from seeds, a large bulb can produce a flower the very next year- with the smaller bulbs it takes maybe a couple of years.And since these bulbs remain viable for quite a long time, even out of the ground, they can be stored-or transported long distances-without much of a problem... which helps explain the spread of tulip cultivation.
At first, tulips were rare in the Netherlands, and only for the wealthy.But in the early seventeenth century, as more bulbs were produced there, you'd think the prices would come down.In fact, though, the popularity of some tulips increased tremendously-so demand soon far exceeded supply, and their prices skyrocketed.And the tulips most prized-for their uniqueness and beauty- were apparently the ones infected by this mysterious virus.At the time, nobody was really able to breed tulips like these. Color breaking happened in just two or three out of a hundred bulbs, and seemingly just by chance.And since you didn't really know, when you bought a bulb, if the colors would break... well, Dutch speculators invested hand over fist... and drove prices sky-high.Some bulbs, even while still in the ground, were sold for as much as you would pay for a house at the time.But the huge speculative bubble created by this tulip craze eventually collapsed, and when the prices fell, that wiped out a lot of fortunes almost overnight.
Later on, tulip breeders learned to duplicate color breaking in healthy, uninfected plants.So the spectacular-looking tulips so common today are the result not of chance viral infections but of carefully controlled breeding.
Professor: Okay. Let's move on, to bacteria and viruses that can infect plants. And let's start out with a virus that's rather common in various plants but first became known in connection with tulips.This virus can cause a change in pigmentation that dramatically affects the color of the plant's leaves or flower petals.But since not all cells of the plant tissue are infected, the result tends to be color variation... with color intensified in one part of the flower petal and faded in another. This is called color breaking.And the virus that causes this in tulips is called the tulip breaking virus.
选项分析：okay let’s move on点明了教授接下来要讲的东西：一种在各种植物里很平常的、但是因为它和郁金香的联系而出名的病毒，之后讲到了这种病毒对荷兰的大规模影响。