Abstract
Soil samples were collectd from different depths of
several selected soil types under both arable and grassland
situations. The production of ethylene in the laboratory
under anaerobic conditions by these soils, in fresh, air
dried and oven dried states were compared. Drying was
found to stimulate ethylene production, oven drying having
most effect on initial ethylene production.
Ethylene formation was related to organic matter content,
ethylene concentrations increasing with increased organic
matter levels. Ethylene concentrations in arable soils
were also related to the acidity, low pH favouring ethylene
production. Grassland soils did not show this relationship.
High levels of added nitrate were found to reduce
ethylene formation but even at 2000 ppm production was
not inhibited completely. Low levels had a transient
inhibitory effect but the maximum level of ethylene produced
was unaffected.
Ethylene formation was stimulated in air dried soil by
the addition of wheat and barley straw and by the addition
of caesin, pepsin, ethanol, lactic acid and pyruvic acid.
The exact nature of this stimulation is not known. Ethylene
production in undried soil depleted of microbial substrates
was promoted by all the three organic substrates supplied:
ethanol, glucose and butyric acid.
Pea plants treated with 1.1 vpm ethylene showed a 50%
reduction in root extension, 4.2 and 10 vpm treatments
inhibited root extension completely.
Exposure of pea and clover plants to air containing
10 vpm. ethylene resulted in a reduction in nodulation and
in the nitrogen fixing capacity of those nodules present.
Fresh and dry weight yields of pea pods and clover stems
were reduced.
