Inhibition of lettuce seed germination and seedling growth by antimetabolites of nucleic acids, and reversal by nucleic acid precursors and gibberellic acid

Germination of White Paris lettuce seeds is inhibited by 2-thiouracil up to 24 hours. This inhibition is reversed by RNA precursors only. Seedling growth of lettuce is inhibited by 2-thiouracil and 5-fluorouracil; and white the effect of 2-thiouracil is counteracted by RNA precursors, inhibition due to 5-fluorouracil is not reversed significantly by any nucleic acid precursors. Possibly 2-thiouracil controls germination and seedling growth by interfering with RNA synthesis, while the effect of 5-fluorouracil is non-specific.In the presence of gibberellic acid, 5-fluorouracil and 2-thiouracil are relatively ineffective in causing inhibition of hypocotyl growth. Mechanism of gibberellic acid action remains obscure.

Repellency of Skin-Surface Lipids of Humans to Mosquitoes

Skin lipids obtained from the washings, in acetone or diethyl ether, of the foreheads or arms of humans are very repellent to female Aedes aegypti when evaluated in a dual-port olfactometer. By means of thin-layer chromatography, the repellent substances can be separated from nonrepellent material also present in skin lipids.