Saturday, June 20, 2009

A smutty tale of exploitation and sex-change

You can easily spot campion flowers that have been infected with anther smut fungus Microbotryum violaceum, because the flower petals are stained with the purplish-brown spores of the fungus (top photograph) that multiply in the plant’s stamens – a symptom that is particularly conspicuous in white campion Silene alba. When the anther smut infects its host it proliferates in the stamens, producing tens of thousands of minute, spiny spores (middle photograph) that are then carried from flower to flower by pollinating insects, like the drone fly that’s visiting the red campion Silene dioica flower in the bottom photograph. Hijacking the plant's stamens and pollinators to produce and spread its spores around would be a remarkable adaptation, but this fungus goes one step further in exploiting its host. Campion plants are either male or female and only males have the stamens that the fungus needs for development of its spores, but when the fungal spores infect a female campion - that wouldn’t normally produce stamens in which the fungal spores proliferate - it induces the female plant to change sex and become male, producing stamens where its spores can multiply.


  1. Hi Phil. The complexity of the interactions at this level is mind boggling. How does the fungus alter the sex of the plant? (Assuming its possible to answer that one in a sentence or two!)

  2. Thanks once again. A.P.O.D. (
    amazes me with the far out. You amaze me with the near wee.



  3. Hi Nyctalus, I think it probably does it by altering the balance of hormones in the plant that control the sex of the flower. Some fungi are known to produce hormones that are also found in plants. There's some academic research interest in this, as if you could identify the chemical signals that the fungus uses it might be possible to apply these to crop plants that produce male and female plants, where you only need a few males for pollination and really want mostly females, because they actually produce the useful crop of seeds or fruits.

  4. Thanks for the link Ron - fantastic pictures, which extend the imagination towards the infinite in the other direction.


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