VOL. 35 ISSUE 2 | THE SCIENTIST 21They left others with intact leaves as con-
trols, and in a third group, they removed
the leaves and instead sheltered the fruit
in a paper bag. The following month, one
of their coauthors collected the fruits from
the experimental plants and sent them to
Sakai, who found that the bare fruit was
less likely to have matured than the fruit
enclosed by leaves or bags (Proc R Soc B,
287:20201718, 2020).
In addition, the researchers found that
the intact vine structures at the higher, cooler
site sported wider leaves than those at the
lower site. The team monitored the temper-
ature inside one plant cup for four days and
found that it was, on average, higher than the
air near a fruit on the same plant that had
been stripped of its enclosing leaves. The
temperature difference was small but sig-
nificant, and was greatest—up to 4.6 °C—at
midday on sunny days. In their paper on thestudy, published in October with Nagaoka as
first author, the researchers dubbed the leafy
enclosure a “green greenhouse.”
The observation that miyama-nigauri
only produces the enclosures late in the
flowering and fruiting season is particu-
larly interesting, notes Atushi Ushimaru,
a plant biologist at Kobe University, in an
email to The Scientist, as it indicates that
the vine “can plastically change flowering
and seeding strategy along the season to
maximize fitness.” Ushimaru has collabo-
rated with Sakai in the past but was not
involved in the current study.
“I think this is a really cool and interest-
ing study,” says Nora Mitchell, who studies
plant biology and evolution at the Univer-
sity of Wisconsin-Eau Claire and was not
involved in the work. Researchers tend to
think of the traits of a plant’s reproduc-
tive parts and its leaves evolving somewhat
separately from one another, she says, but
“this paper was really interesting in tying
together some of those reproductive and
vegetative traits, and how they can inter-
act.” That said, it’s not the first knowninstance of leaves assisting in reproduc-
tion. Plants such as dogwoods have colored
leaves called bracts that, like petals, serve to
attract pollinators to flowers.
In her current work, Sakai is inves-
tigating whether there is a connection
between the leaf enclosures and another
miyama-nigauri trait, one observed by
Junichi Akimoto, the student who passed
away in the 1990s. The vine comes in
two sexes, male and hermaphrodite, and
Akimoto had found that the proportion
of individuals in each category varies
with altitude, with fewer males growing
at higher sites. Sakai is now working on
finding out why. She posits that it may
be tied to the fact that the plant cups are
thicker at higher altitudes, which might
prevent pollen from escaping, making it
difficult for males to reproduce.
Nagaoka, now 91, has continued his
observations of miyama-nigauri, Sakai
says, and still sometimes sends her photos
of the plant. “I was impressed very much
by his love and enthusiastic attitude.”
SAKAI SHOKO —Shawna Williams
A RARE FIND: Observations of the new leaf
formation were made by Nobuyuki Nagaoka,
a retired schoolteacher living near the foot of
Mount Gassan in Japan.