By Wendy Langhans
Fresh, ripe, jucy tomatoes. I’ll bet, if close your eyes right now, you can recall the smell. Maybe, your mouth is watering just a little bit too. But we’re not the only living things that are attracted to the scent of ripe tomatoes. Their smell also attracts certain plants. Plants? Yes – specifically – dodder plants.
According to University of California’s Integrated Pest Management Program, there are about 150 different species of dodder worldwide. It is estimated that each year, dodder costs California farmers $4 million in reduced tomato crops. Dodder is a parasitic plant – the green equivalent of Dracula. When dodder seeds sprout, they do not put down roots into the soil. Instead, their stems lengthen, twist and turn and seek out a nearby host plant. They attach their root-like haustoria to the host’s stem, penetrate it, and suck out water and nutrients.
But a dodder seedling has only a limited amount of time to find and attach itself to a plant. “A dodder seedling can survive several days without a host, but if it doesn’t come into contact with one within 5 to 10 days, the seedling will die.” So how does dodder find a tomato plant? By sniffing it out.
During photosynthesis, tomato plants release watery vapor through the process of transpiration. This vapor also contains volatile (perfume-like) chemicals, which are recognized by dodder (and hungry humans).
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Scientists at Penn State discovered that dodder “has the ability not only to recognize its prey by scent but also to move toward it with a remarkable accuracy and efficiency.” As described in this NYT’s article, they “extracted volatile chemicals from the tomato plants and found that the dodder shoots would grow toward the chemicals even in the absence of a plant.” To watch a dodder seek out a tomato plant, check out this short video.
These researchers also discovered that “another chemical compound from wheat actually repels the dodder seedlings”. Perhaps I should consider saving the water I use to boil pasta. Who knows, it might be useful for watering my tomato plants – the “Green Dracula” equivalent of garlic.
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