grew faster, but anomalies of
high solar radiation and atmo-
spheric water demand reduced
tree growth. Fast-growing trees
and drier forests were also more
sensitive to dry periods, which
are increasing over time. This
study shows the potential for
climate change to limit carbon
storage in tropical forests.
—BEL
Glob. Change Biol. 10.1111/
gcb.15982 (2021).
METABOLOMICS
Panning for metal-bound
small molecules
Because of their important
role as cofactors and their high
reactivity, microbes devote con-
siderable energy and biosynthetic
resources to producing small
molecules that aid in solubiliza-
tion, transport, and chaperoning
of transition metal ions. Aron
et al. developed a native mass
spectrometry method that
enables the identification of these
compounds. By adjusting the
pH and adding metal salts after
chromatographic separation but
before ionization, the authors
were able to identify metal-bound
complexes in culture extracts
and complex samples. Iron-
binding siderophores were easily
observed in various contexts, as
were several known zinc- and
copper-binding molecules. Metal
sequestration is a common
antimicrobial strategy, and this
approach may provide insights
into how microbes acquire scarce
metal ions. —MAF
Nat. Chem. 10.1038/
s41557-021-00803-1 (2021).PHYSICS
Dots simulate
magnetism
Engineered quantum systems
can be used to simulate the
complex many-body phys-
ics that is difficult to probe in
“real” materials or to calculate
using classical computers.
Atomic systems, including
cold atoms in optical lattices
and trapped ions, have been at
the forefront of this quantum
simulation effort. In a comple-
mentary development, van
Diepen et al. used a solid-state
system, a linear array of quan-
tum dots in a GaAs–AlGaAs
heterostructure, to simulate
quantum magnetism. By con-
trolling the potentials of the
four quantum dots in the array,
the researchers were able totune the exchange interactions
between the single electrons
occupying each dot. The
method may be generalizable
to longer arrays and different
lattice geometries. —JS
P h y s. Rev. X 11 , 041025 (2021).CANCER
A gene target for
bile duct cancer
Cholangiocarcinomas are rare
and highly aggressive cancers
that occur within bile ducts.
Activation of the fibroblast
growth factor receptor 2
(FGFR2) pathway is frequently
observed for those bile duct
tumors that occur within the
liver (intrahepatic cholangio-
carcinoma) and show mixed
therapeutic responses. Cleary
et al. performed genomic anal-
ysis of several hundred biliary
tract cancers and discovered
a new class of recurrent
mutations in the FGFR2 gene.
FGFR2 extracellular domain
in-frame deletions were found
to be an alternative mecha-
nism of FGFR2 activation and
oncogenic transformation that
was experimentally targeted
by treatment with FGFR inhibi-
tors. —PNK
Cancer Discov. 11 , 2488 (2021).ORGANIC CHEMISTRY
Aldehyde deuteration
Replacing hydrogen in organic
molecules with its heavier
deuterium isotope is a widely
used strategy for studying
drug metabolism and chemical
mechanisms more broadly.
Gadekar et al. sought to
optimize deuterium incorpo-
ration at the carbonyl site of
benzaldehyde derivatives, a
challenging compound class
for this reaction. By correlating
rates with a variety of param-
eters associated with both the
substrates and N-heterocyclic
carbene catalysts, the
authors were able to maxi-
mize deuteration efficiency
while minimizing a competing
coupling reaction between the
aldehydes. —JSY
ACS Catal. 11 , 14561 (2021).10 DECEMBER 2021 • VOL 374 ISSUE 6573 1337Epiphytic plants tend to have thicker leaves
to help conserve water and nutrients.SCIENCE science.org
PLANT ECOLOGYSurvival traits
for the treetops
E
piphytes, plants that grow
on the stems and branches
of other plants, account for
about 10% of all vascular
plants. However, knowledge
of their biology has lagged that of
ground-rooted plants. To address
this lack, Hietz et al. assembled
data on the functional traits of
almost 3000 epiphytic species,
mainly from the neotropics.
The authors found that epiphytes
typically have lower photo-
synthetic rates than trees and
ground-rooted herbs and lower
leaf nitrogen content. These traits
mean that epiphyte leaves tend
to be thick and retain more
water, reflecting the constraints
of the nutrient and water supply in
the forest canopy. Although this
work draws together much-
needed data on epiphyte leaf
traits, much remains to be learned
about the root physiology and
reproductive habits of these
plants. —AMS
J. Ecol. 10.1111/1365-2745.13802 (2021).