Harlan K. Pratt

Stimulation of rice coleoptile growth by ethylene.

SummaryThe growth rate of rice coleoptiles is increased by low concentrations of ethylene, especially in oxygen concentrations lower than air; carbon dioxide enhanced this response. C2H4 is produced by rice seedlings, and this production is also enhanced by carbon dioxide. Ethane and propane were produced in trace amounts but were inactive in growth stimulation as were also methane, propylene, and butane.

An effect of ethylene on swelling of isolated mitochondria

Mitochondria from rat livers and cauliflower buds were used as model systems to determine if ehtylene treatments applied in vitro could induce changes in properties of lipoprotein membranes leading to increased permeability. The rate of mitochondrial swelling under different treatments was followed by spectrophotometric measurements of changes in the scattering of light by mitochondrial suspensions. Ethylene treatments applied in buffered test solutions of KCl increased the rate of swelling; no increase was observed in sucrose solutions. Calcium ions and carbon tetrachloride caused more rapid swelling than did ethylene. Apparently, ethylene can induce a limited change in membrane permeability. If the mitochondrial membrane is a factor in the regulation of respiration in plant cells, the respiratory response induced in plants by ethylene may be the result of increased membrane permeability.

Ethylene formation from α-keto-γ-methylthiobutyrate by tomato fruit extracts

Abstract Cell-free extracts prepared from tomato fruits ( Lycopersicon esculentum Mill.) were not capable of catalyzing ethylene production from α-keto-γ-methylthiobutyrate, in the presence of Mn 2+ , sulfite, and phenol, until an endogenous heat-stable and dializable inhibitor was removed. After its removal, the enzyme-catalyzed formation of ethylene was readily demonstrated. Many of the properties of this tomato enzyme system relevant to ethylene production were found to be similar to those of the horse-radish peroxidase system.

The effect of kinetin and naphthalenacetic acid upon localized accumulation as related to senescence in detached leaves

SummaryNaphthaleneacetic acid, when applied together with kinetin to defined areas of detached leaves of Xanthium pensylvanicum Wallr. or broccoli (Brassica oleracea L., var. italica), reduced the senescence-retarding effect of kinetin but synergistically increased the kinetin-induced accumulation of 14C from labeled glycine. Naphthaleneacetic acid by itself did not accelerate senescence. The ability of kinetin to delay senescence in these detached leaves therefore can not be explained as a result of the gross accumulation (“mobilization”) of protein precursor.