Plant olfaction - Plants smell?

Common dodder (Cuscuta pentagona)

Cuscuta pentagona is not your normal plant. It is a spindly orange vine that it basically has no leaves. What's unique about Cuscuta is that it isn’t green, because it lacks chlorophyll, the pigment that absorbs solar energy, allowing plants to turn light into sugars and oxygen through photosynthesis. Cuscuta gets its food from its neighbors; it is a parasitic plant. In order to live, Cuscuta attaches itself to a host plant and sucks off the nutrients provided by the host by burrowing an appendage into the plant’s vascular system. What makesCuscuta truly fascinating is that it has culinary preferences: it chooses which neighbors to attack.

The way Cuscuta does this is through its sense of smell. Yes Cuscuta, like all plants, can sense volatile chemicals in the air, just like we can sense, can smell, bleach that's been used to wash a floor, a neighbor's barbecue a few houses down the street, or a new perfume squirted into the air. Cuscuta uses the smell of neighboring plants to find the tastiest one to attach on to. Cuscuta tells the difference between plants by the way they smell; Cuscuta can differentiate between tomato and wheat, and given the choice will prefer a tomato plant!

You can read more about Cuscuta and a plant's sense of smell here, or in Chapter 2 of WHAT A PLANT KNOWS.

Pretty but poisonous

Sophora secundaflora (Texas mountain laurel)

The Texas Mountain Laurel is a lovely small tree with bunches of bright blue flowers. These flowers yield bright red seeds which Native Americans used as ornaments and jewelry, but also as an hallucinogen. The seeds can be used to make a drink which when dilute leads to hallucinations, but at higher doses is poisonous. The toxic compound, cytisine, causes paralyses which leads to suffocation.

Very, very old plants

~1500 year-old Welwitschia mirabilis 

The Welwitschia plant from the Namibia dessert can live for up to 2000 years. What's really strange is that the leaves of Welwitschis are the parts that keep growing continuously. While the tips of the leaves eventually fray and die, the base keeps growing, pushing out new parts of the same leaf sort of like a vegetal pasta machine!