Nas referências que encontrei, parece ser usada como sinônimo de "seedlings".

[Houston is under water, my seedlets are drowned and I'm sick (again)...
We've had a ton of rain over the last couple of days. Some parts of Houston got 11 inches last night, we got about 4 but it was torrential. We had just transplanted the squash, zucchini, eggplant and half the peppers Sunday because it wasn't supposed to be this bad.]
http://idigmygarden.com/forums/showthread.php?t=17809
Comentário: se eles tinham acabado de transplantar as "seedlets", elas não eram mais sementes, já tinham germinado.



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Note added at 3 horas (2009-06-10 20:41:02 GMT)
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Mudas jovens:
[Oil palm seedlets of 4 - 5 leaf stage and nine month old seedlings...]
http://ajol.info/index.php/joafss/article/view/33718

[As a result, the farmers are asking for pre-germinated seedlets, which they could nurse for themselves, close to the farm. ...]
http://www.seed-narsarah.org/AnnualReport2007.doc

[We've purchased our baby plants (Seedlets) from a local supplier. ...]
http://hu-hu.facebook.com/note.php?note_id=82706649094