Scientifically Speaking: The killer hiding in plain sight
For more than a century, botanists collected an alpine flower with dead insects still attached. A new study has finally shown that the plant was eating them.
Researchers conducted an analysis of all 45 preserved flowering specimens of Saxifraga candelabrum at the Kunming Institute of Botany, collected between 1888 and 2016. The insects found on 43 of these specimens provided evidence of the plant's carnivorous nature, which had puzzled botanists for generations. A study published in Nature Communications now explains the mystery behind this phenomenon.
The Saxifraga candelabrum, a plant that grows in nutrient-poor rock crevices in the mountains of southwestern China, is capable of trapping small insects with its tiny, reddish sticky hairs. Within these hairs, a digestive enzyme actively works, allowing nutrients from the insects' bodies to enter the plant. This carnivorous behavior was first described by Charles Darwin in his 1875 publication Insectivorous Plants.
The researchers observed that mature plants trapped an average of 71 insects, mostly tiny non-biting midges. Plants with longer flowering branches tended to capture more insects. Field experiments showed that insects were attracted to the flowers, both by their visual cues and the floral scents they emitted. However, larger pollinators like flies and bees usually escaped while small midges were trapped by the sticky hairs.
To confirm the plant's carnivorous behavior, the researchers tested the sticky hairs for phosphatase enzyme activity, which is common in carnivorous plants. They found that the enzyme was active in the plant's hairs but not in a closely related species. Additionally, the researchers placed fruit flies enriched with a traceable form of nitrogen onto the plant's hairs and measured the nitrogen uptake in the plant's tissues. The results showed that the plant absorbed the nitrogen, while two non-carnivorous species did not.
The plant's nitrogen acquisition through insect trapping is crucial for its survival in the nutrient-poor alpine soils where it grows. Once the plant flowers and dies, the nutrients obtained from insects are directed towards its reproductive effort. This discovery suggests that there may be more carnivorous plants yet to be discovered, particularly in regions like the Indian Himalayan region, where extensive historical plant collections exist.
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