🚀 go-pugleaf

In article <20030204014538.11123.00000116@mb-dh.aol.com>, seanhoutma@aol.comnose (Sean Houtman) wrote:
>From: Judith Baltsar judith.baltsar@gmx.de 
>
>>Hello everybody,
>>while contemplating on the dispersal types of a great number of plants
>>(see my other posting) I stumbled over the question what primary
>>function the awn of poaceae might have. It is often noted that it
>>might assist in epizoochorous dispersal (attatching the seed to the
>>fur of some animals) or with strong hygroscopic movements it might
>>"crawl" on the ground or even drill itself into the soil. But are
>>these the primary functions or just some nice side effects (kind of
>>spandrels of San Marco)?
>
>I can verify that in the long awned species of Stipa, it is definitely used in
>drilling the seed into the soil. Since the awn is genuflected, it holds the
>caryopsis at an angle, and vibration from the wind pushes the seed into the
>soil, aided by the hairs on the callus. When the seed has been pushed in far
>enough, the awn breaks off and blows away. It is perfectly adapted for this
>function. Other grasses certainly use the awns in other ways, not all of them
>apparent.

Yeah, lots of tropical grasses with awns use them to "plant 
themselves" too -- but it can also be a response to wetness (or just 
humidity?).  When wetted, they twirl around until stopped by 
vegetation or debris or whatever, then the forces involved act to push 
the seed itself into the soil.


Cheers, Phred.

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