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Questions 43-52 are based on the following conditions hundreds of millions of photons strike

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passage and supplementary material. 45 each square millimeter of ground each second, this
This passage is adapted from Peter A. Ensminger, Life Under
illumination is below the threshold needed to
the Sun. ©2001 by Peter A. Ensminger. stimulate the germination of most seeds.
Hartmann says that he was very skeptical when
Many millennia before the invention of he first came up with this idea because he assumed
herbicides, farmers simply plowed their fields to 50 that such a simple method of weed control as
control weeds. Even today, plowing can constitute a plowing at nighttime must be ineffective or it would
Line valuable part of an integrated weed-management have been discovered long ago. But the subsequent
5 program. Although plowing kills standing weeds, experiments, first presented at a 1989 scientific
farmers have long known that it often leads to the meeting in Freiburg, Germany, clearly demonstrated
emergence of new weed seedlings in a few weeks. 55 that the method can be effective.
Ecologists have shown that a farmer’s field can Hartmann tested his idea by plowing two
have 50,000 or more weed seeds per square meter agricultural strips near Altershausen, Germany.
10 buried beneath the soil surface. Plant physiologists The farmer Karl Seydel cultivated one strip, repeated
have shown that seeds buried more than about one threefold, at around midday and the other strip
centimeter below the soil surface do not receive 60 at night. No crops were planted in these pilot
enough light to germinate. Do the blades of a plow, experiments, to avoid possible competition with
which can reach more than a foot beneath the soil the emerging weeds. The results were dramatic.
15 surface, bring some of these buried seeds to the More than 80 percent of the surface of the field
surface where their germination is induced by plowed in daylight was covered by weeds, whereas
exposure to sunlight? 65 only about 2 percent of the field plowed at night was
Two ecologists, Jonathan Sauer and Gwendolyn covered by weeds.
Struik, began to study this question in the 1960s. In a This method of weed control is currently being
20 relatively simple experiment, they went to ten used by several farmers in Germany. Because many
different habitats in Wisconsin during the night and of the same weed species that invade farmers’ fields
collected pairs of soil samples. They stirred up the 70 in Germany also invade fields elsewhere in the world,
soil in one sample of each pair in the light and stirred this method should be successful elsewhere. In fact,
up the other sample of each pair in the dark. They then recent studies at universities in Nebraska, Oregon,
25 exposed all ten pairs to natural sunlight in a Minnesota, Denmark, Sweden, and Argentina
greenhouse. For nine of the ten pairs of soil samples, support this idea.
weed growth was greater in the samples stirred up in
light. They concluded that soil disturbance gives
weed seeds a “light break,” and this stimulates their
30 germination.
More recently, Karl Hartmann of Erlangen
University in Germany reasoned that when farmers
plowed their fields during the day, the buried weed
seeds are briefly exposed to sunlight as the soil is
35 turned over, and that this stimulates their
germination. Although the light exposures from
plowing may be less than one millisecond, that can
be enough to induce seed germination. Thus the
germination of weed seeds would be minimized if
40 farmers simply plowed their fields during the night,
when the photon fluence rate [the rate at which
photons hit the surface] is below 1015 photons per
square meter per second. Although even under these

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Number of Emerged Seedlings in Soil Samples 45

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One Month after Soil Was Disturbed
As used in line 16, “induced” most nearly means
Number of emerged
seedlings in soil A) lured.
Sample Source of soil
disturbed in B) established.
light darkness C) convinced.
A deciduous woods 4 0
D) stimulated.
B deciduous woods 2 1
C deciduous woods 6 2
D conifer plantation 8 3 46
E conifer plantation 2 1
F tall-grass prairie 5 1 Which choice best supports the idea that seeds
G old pasture 0 2 present in fields plowed at night are exposed to some
H old pasture 2 1 amount of light?
I muck field 14 2 A) Lines 31-36 (“More . . . germination”)
J muck field 5 3 B) Lines 36-38 (“Although . . . germination”)
Adapted from Jonathan Sauer and Gwendolyn Struik, “A Possible C) Lines 43-47 (“Although . . . seeds”)
Ecological Relation between Soil Disturbance, Light-Flash, and Seed
Germination.” ©1964 by Jonathan Sauer and Gwendolyn Struik.
D) Lines 48-52 (“Hartmann . . . ago”)

47
43 The passage suggests that if Seydel had planted wheat
According to the passage, exposure to light allows or corn on the two agricultural strips in Hartmann’s
seeds to experiment, the percentage of the surface of each
strip covered with weeds would likely have been
A) begin to develop.
A) lower than the percentage that Hartmann found.
B) absorb necessary nutrients.
B) higher than the percentage that Hartmann had
C) withstand extreme temperatures. predicted.
D) achieve maximum growth. C) nearly impossible for Hartmann to determine.
D) comparable to Hartmann’s original projection.
44
The question in the second paragraph (lines 13-17) 48
primarily serves to
Which choice provides the best evidence for the
A) emphasize the provisional nature of the findings answer to the previous question?
discussed in the passage.
A) Lines 56-60 (“Hartmann . . . night”)
B) introduce the specific research topic addressed in
the passage. B) Lines 60-62 (“No crops . . . weeds”)
C) suggest the hypothetical impact of the studies C) Line 62 (“The results . . . dramatic”)
analyzed in the passage. D) Lines 63-66 (“More . . . weeds”)
D) indicate the level of disagreement about the
methods explored in the passage.

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49 51

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As used in line 62, “dramatic” most nearly means As presented in the table, which sample produced the
most seedlings when the soil was disturbed in light?
A) theatrical.
B) sudden. A) Sample G
C) impressive. B) Sample H
D) emotional. C) Sample I
D) Sample J

50
52
According to the table, in which soil sample
disturbed in darkness did the fewest number of The data presented in the table most directly support
seedlings emerge? which claim from the passage?
A) Sample A A) Lines 1-3 (“Many . . . weeds”)
B) Sample B B) Lines 8-10 (“Ecologists . . . surface”)
C) Sample C C) Lines 10-13 (“Plant . . . germinate”)
D) Sample D D) Lines 38-43 (“Thus . . . second”)

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