PERPLEXED by the sparsity of plant life immediately surrounding the Great
Barrier Reef, two Queensland biologists may have stumbled on a clutch of new,
natural weedkillers that appear to be harmless to people, animals and crop
plants.
Jim Burnell, a molecular biologist from James Cook University, was out
scuba-diving on the reef, which runs along the coast of Queensland, when it struck him
that the coral was extremely bare in places. 鈥淓verything on the reef was
thriving except for free-growing seabed plants,鈥� he told 快猫短视频.
He and his colleague Lyndon Llewellyn from the Australian Institute of Marine
Science at Cape Ferguson speculated that some animals inhabiting the reef could
be secreting chemicals that prevent plant growth, perhaps to stop plants
clogging their habitat.
The pair screened about 5000 samples from many reef organisms. Now they have
isolated a group of compounds that disable an enzyme specific to photosynthesis
in the group of plants classified by biologists as C4. This class of
plants include almost all important weed species鈥攑lants that grow faster
than crop plants.
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Most commercial crops are plants of the C3 variety, which use carbon
dioxide directly from the atmosphere to manufacture sugar in their leaves, where
the process is subject to interference from oxygen. But C4 plants throw
in an intermediate step: they take up carbon dioxide as bicarbonate and
transport it to an intracellular compartment where sugars can be made, isolated
from oxygen. This makes C4 photosynthesis more efficient, and means
that under warm, light conditions C4 plants grow wildly and
profusely鈥攍iterally like weeds.
A joint research team led by Burnell and Llewellyn found the weedkilling
compounds by looking for those extracts which inhibited an enzyme that is
crucial to C4-style operation. They found 60 active extracts from which
they have so far analysed the structure of four active鈥攁nd
耻苍谤别濒补迟别诲鈥攃辞尘辫辞耻苍诲蝉.
In greenhouse experiments, the compounds鈥攚hose identity is under wraps
until patents are filed鈥攌ill only C4 plants when painted on the
leaves. If they are as selective in the field, the researchers say, a herbicide
developed from them could be sprayed on crops just when needed, because it would
only affect the weeds. The idea has yet to be tested.
Burnell says any herbicide developed from the new reef compounds would be
very different from glyphosate, the most widely used crop herbicide, to which
many weeds are becoming resistant. Given the chemical is already part of the
reef environment, it should be easily biodegradable, Burnell argues, and also be
harmless to fish, which are particularly sensitive to many current herbicides.
This is important because much herbicide ends up in rivers and seas.