- Saxifrage candlestickan alpine flowering plant from China, has been confirmed as a carnivorous plant because it attracts, traps, digests and absorbs nutrients from insects.
- Experiments showed the digestive system Enzyme activity They track nitrogen from labeled fruit flies into plant tissues, providing direct evidence that prey are contributing nutrients.
- The discovery revives an idea put forward by Charles Darwin in 1875 and suggests that carnivory may be more widespread among flowering plants than scientists currently acknowledge.
The sticky hairs covering an alpine flower in southwest China do more than just hamper passing insects. They help Saxifrage candlestick They obtain nutrients from their prey, making them among the world’s proven plants Carnivorous Classify.
The discovery adds both saxifrage The broader plant order Saxifragales is the best-known variety of carnivorous plants.
Inference requires more than simply observing the insects attached to the plant. To qualify as a carnivore, a species must exhibit adaptations to attract, capture, digest, and absorb nutrients from prey.
Saint Candlestick He met every part of this test.
The work also goes back to a question posed by Charles Darwin in 1875. Some suspected saxifrage The species may be carnivorous because its glandular hairs can catch insects. However, his own nutritional experiments did not produce any conclusive evidence.
The sticky bristles regularly capture insect prey
Saxifrage candlestick It grows in the alpine parts of the Qinghai-Tibet-Hengduan mountain region. It occurs in central and northern Yunnan and southwestern Sichuan, often in nutrient-poor rock crevices.
Its flowering stems and branches bear glandular hairs covered with a sticky secretion.
Field observations showed that mature plants retained an average of 71 Insects. Small mosquitoes of the Chironomidae family make up a significant portion of the prey.
The researchers also examined 45 flowering herbaceous specimens collected between 1888 and 2016. The insects remained attached to the glandular hairs in 43 of those samples.
This century-long record suggests that prey capture was not an unusual event caused by a single location or season.
The amount of captured prey also increased with the size of flowering branches. Juvenile plants with relatively few branches trap few or no insects.
The scent appears to help bring insects closer
The team then tested whether the insects merely bumped into or were attracted to the sticky plants.
Some flowering plants were surrounded by transparent glass that preserved their appearance and masked their smell. Others were surrounded by a breathable white mesh that concealed their appearance while allowing odor to escape.
Insects visited untreated plants and visually hidden plants more often than odor-blocked plants and controls. Visitation to visually hidden plants was significantly higher than to plants whose scent was masked.
The result pointed to the scent of flowers as one of the factors contributing to attraction.
Chemical analysis discovered multiple volatile compounds, including beta-myrcene and eucalyptol, which could contribute to attracting insects.
The plant also seems to avoid catching many insects that are beneficial to it Pollination.
Most of the trapped prey were small insects, particularly Chironomidae. Larger insects from groups including Calliphoridae, Halictidae, Muscidae, Syrphidae, and Tachinidae were effective pollinators and were rarely hunted.
This separation allows the same flowering structures to perform two roles, capturing small insects while leaving larger pollinators largely unharmed.
Enzymes reveal the mechanism of digestion
Trapping prey still hasn’t been proven Saint Candlestick can be digested.
Therefore, researchers looked for phosphatase activity. This enzyme helps release nutrients and is commonly shown in studies of carnivorous plants.
Fluorescence tests showed phosphatase activity in the glandular hairs found on the plant’s leaves, stems, and calyxes.
The same signal appeared in Pinguicula primulifloraIt is a known carnivorous plant used as a positive control. A closely related non-carnivorous species, Saxifraga filiculisNo detectable fluorescence appeared under the same conditions.
The experiment was repeated three times with similar results.
These results provided evidence that sticky hairs do more than just immobilize insects. They own digestive An activity capable of assisting in the destruction of prey.
Nitrogen transfer from fruit flies to plants
The most powerful test follows nutrients directly from insects to plant tissues.
The researchers raised more than 1,000 fruit flies for about two months on food containing nitrogen enriched with the stable isotope ¹⁵N. Another 500 flies were reared naturally.
60 field trials included Saint Candlestick Factories from three locations in Shangri-La, Yunnan. 20 other stations underwent laboratory tests.
The researchers also included known species of carnivores, Drosera peltataand two non-carnivore controls.
Plants generally received 10 labeled fruit flies.
After breastfeeding both Saint Candlestick and D. platata showed significant increases in labeled nitrogen. The two non-carnivorous species did not.
The soil is close to being treated Saint Candlestick Plants remained low in ¹⁵N. This helped rule out the possibility that the labeled substances entered the soil first and reached the plants through their roots.
The researchers also excluded tissue that had direct contact with the flies to reduce the possibility that the result could be explained by surface contamination.
inside Saint CandlestickFlowers showed the greatest amount of nitrogen, followed by stem leaves and basal leaves.
The pattern indicates that prey-derived nutrients have moved beyond the original trapping surface and entered other tissues.
Carnivory also appears in the genome
Genetic evidence added another layer to the case.
The team has assembled a chromosome-wide genome for Saint CandlestickIt is estimated at about 2.24 billion base pairs.
Comparisons with other carnivorous plants have revealed related gene families victim Attraction, digestion and absorption of nutrients. The researchers also discovered examples of convergent genetic change between independently evolving carnivore lineages.
When comparisons were made between carnivorous plants with different hunting systems, some common genotypes remained while others differed.
This combination suggests that carnivores evolved independently several times, sometimes using similar genetic solutions but following different evolutionary paths.
Practical implications of the research
to be sure Saint Candlestick Carnivores also expand the known range of plant groups they access Nutrients From animal prey.
It also gives researchers a new system to study how carnivores evolved in flowering plants, especially outside the humid environments often associated with carnivorous species.
Other members of saxifrage They also have sticky glandular hair. The new findings raise the possibility that some of them may merit careful testing for digestion and nutrient absorption.
The work also shows why trapping insects alone cannot fix carnivory. A combination of field observations, enzyme tests, isotope tracing, and genetic analysis provided a much stronger case.
More than 150 years after Darwin wondered whether this was possible saxifrage It can cross the line from passive plant to active predator, Saint Candlestick Provides a clear example.
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