Osmotic pressure influence in germination tests for antibiosis.

A common test for the presence of toxic organic substances in plant tissues, and therefore of the potential role of antibiosis (specifically allelopathy) in native plant cozmmunities, has been to apply a water extract of the tissues in germination tests of cultivated annuals. The observed osmotic pressure of the extracts can be high, and sucrose solutions of similar osmotic pressure result in a depression of germnination and early development. Thus in the aforementioned type of test, extracts must be diluted to an osmotic pressure no greater than 0.5 atmopheres.