Dk. Pandey, INHIBITION OF SALVINIA (SALVINIA-MOLESTA MITCHELL) BY PARTHENIUM (PARTHENIUM-HYSTEROPHORUS L) .1. EFFECT OF LEAF RESIDUE AND ALLELOCHEMICALS, Journal of chemical ecology, 20(12), 1994, pp. 3111-3122
Parthenium (Parthenium hysterophorus L.) leaf residue (LP, leaf powder
) inhibited salvinia (Salvinia molesta Mitchell) biomass and the numbe
r of healthy fronds at 0.25% (w/v) and killed the treated plants at an
d above 0.75% (w/v) in about 5-15 days, depending on the quantity of t
he residue. At the lethal dose, the LP caused an abrupt desiccation of
above-water plant parts, probably due mainly to root dysfunction. Thi
s was concurrent with the loss of dehydrogenase activity in, and an in
crease in solute leakage from, the roots and loss of chlorophyll a, b,
and total chlorophyll contents in the fronds, resulting in death of t
he treated plants. The LP appears inhibitory to salvinia through affec
ting macromolecules-proteins, lipids, and nucleic acids. The inhibitor
y activity of LP at the lethal dose suspended in water was completely
lost when allowed to stand for 30 days under outdoor conditions and pr
omoted growth of the salvinia plants placed in it, The standard allelo
chemicals, including those present in parthenium LP, except parthenin
and p-hydroxybenzoic acid, did not inhibit growth up to 100 ppm. Howev
er, parthenin and p-hydroxybenzoic acid killed salvinia plants at 100
and 50 ppm, respectively. Since p-hydroxybenzoic acid is unlikely to b
e present at such a high concentration, parthenin appears to be one of
the main allelochemicals responsible for the inhibitory effect of par
thenium leaf residue on salvinia.