SAT OG 2018 Reading - Test 6 reading 3

Questions 22-32 are based on the following

This passage is adapted from Elsa Youngsteadt, “Decoding a Flower’s Message.” ©2012 by Sigma Xi, The Scientific Research Society.

Texas gourd vines unfurl their large, flared

blossoms in the dim hours before sunrise. Until they

close at noon, their yellow petals and mild, squashy
aroma attract bees that gather nectar and shuttle
5 pollen from flower to flower. But “when you

advertise [to pollinators], you advertise in an

open communication network,” says chemical

ecologist Ian Baldwin of the Max Planck Institute for

Chemical Ecology in Germany. “You attract not just
10 the good guys, but you also attract the bad guys.” For

a Texas gourd plant, striped cucumber beetles are

among the very bad guys. They chew up pollen and

petals, defecate in the flowers and transmit the

dreaded bacterial wilt disease, an infection that can
15 reduce an entire plant to a heap of collapsed tissue in

mere days.
In one recent study, Nina Theis and Lynn Adler

took on the specific problem of the Texas

gourd—how to attract enough pollinators but not
20 too many beetles. The Texas gourd vine’s main

pollinators are honey bees and specialized squash

bees, which respond to its floral scent. The aroma

includes 10 compounds, but the most

abundant—and the only one that lures squash bees
25 into traps—is 1,4-dimethoxybenzene.
Intuition suggests that more of that aroma should

be even more appealing to bees. “We have this

assumption that a really fragrant flower is going to

attract a lot of pollinators,” says Theis, a chemical
30 ecologist at Elms College in Chicopee,

Massachusetts. But, she adds, that idea hasn’t really

been tested—and extra scent could well call in more

beetles, too. To find out, she and Adler planted

168 Texas gourd vines in an Iowa field and,
35 throughout the August flowering season, made half

the plants more fragrant by tucking

dimethoxybenzene-treated swabs deep inside their

flowers. Each treated flower emitted about 45 times

more fragrance than a normal one; the other half of
40 the plants got swabs without fragrance.
The researchers also wanted to know whether

extra beetles would impose a double cost by both

damaging flowers and deterring bees, which might

not bother to visit (and pollinate) a flower laden with
45 other insects and their feces. So every half hour

throughout the experiments, the team plucked all the

beetles off of half the fragrance-enhanced flowers and

half the control flowers, allowing bees to respond to

the blossoms with and without interference by
50 beetles.
Finally, they pollinated by hand half of the female

flowers in each of the four combinations of fragrance

and beetles. Hand-pollinated flowers should develop

into fruits with the maximum number of seeds,
55 providing a benchmark to see whether the

fragrance-related activities of bees and beetles

resulted in reduced pollination.
“It was very labor intensive,” says Theis.

“We would be out there at four in the morning, three
60 in the morning, to try and set up before these flowers

open.” As soon as they did, the team spent the next

several hours walkingfrom flower to flower,

observing each for two-minute intervals “and writing

down everything we saw.”
65 What they saw was double the normal number of

beetles on fragrance-enhanced blossoms.

Pollinators, to their surprise, did not prefer the

highly scented flowers. Squash bees were indifferent,

and honey bees visited enhanced flowers less often
70 than normal ones. Theis thinks the bees were

repelled not by the fragrance itself, but by the

abundance of beetles: The data showed that the more

beetles on a flower, the less likely a honey bee was to

visit it.
75 That added up to less reproduction for

fragrance-enhanced flowers. Gourds that developed

from those blossoms weighed 9 percent less and had,

on average, 20 fewer seeds than those from normal

flowers. Hand pollination didn’t rescue the seed set,
80 indicating that beetles damaged flowers directly

—regardless of whether they also repelled

pollinators. (Hand pollination did rescue fruit

weight, a hard-to-interpret result that suggests that

lost bee visits did somehow harm fruit development.)
85 The new results provide a reason that Texas gourd

plants never evolved to produce a stronger scent: “If

you really ramp up the odor, you don’t get more

pollinators, but you can really get ripped apart by

your enemies,” says Rob Raguso, a chemical ecologist
90 at Cornell University who was not involved in the

Texas gourd study.

Question 22 The primary purpose of the passage is to