We have identified through bioassay guided isolation an allelochemical, eudesmane-type sesquiterpeniod, 3beta-caffeoxyl-beta1,8alpha-dihydroxyeudesm-4(15)-ene (1), from an endemic plant species growing in the Himalayas. In our search for the bioactive subfraction, the hexane one was highly significant, showing 100% inhibition of lettuce seed growth at 100 ppm while other subfractions (chlorofor...

Thermoinhibition, or failure of seeds to germinate at warm temperatures, is common in lettuce (Lactuca sativa) cultivars. Using a recombinant inbred line population developed from a lettuce cultivar (Salinas) and thermotolerant Lactuca serriola accession UC96US23 (UC), we previously mapped a quantitative trait locus associated with thermoinhibition of germination to a genomic region containing ...

Preparation and characterization of antisera against lettuce (Lactuca sativa L., cv. Grand Rapids) and pea (Pisum sativum L., cv. Alaska) phytochrome is described. These antisera, together with previously obtained antisera against zucchini (Cucurbita pepo L., cv. Black Beauty) and oat (Avena sativa L., cv. Garry) phytochrome, were used to compare by Ouchterlony double immunodiffusion phytochrom...

Leafy vegetables, such as lettuce ( Lactuca sativa L), have been identified as a potential source of perchlorate exposure to humans. Perchlorate is of concern because excessive amounts may impair thyroid function by inhibiting iodide uptake by the sodium iodide symporter. Perchlorate has been identified as an oxidation product in sodium hypochlorite. Dilute hypochlorite solutions are widely use...

In previous studies we proposed the plant leaf fatty acid composition, and more precisely the ratio C18:3/(C18:0 + C18:1 + C18:2) as a tool to diagnose soil contamination ex situ. These studies led us to normalize this parameter as a biomarker of soil quality using Lactuca sativa growing under controlled conditions as the plant model species. The evaluation of the toxic effects of pollutants is...

In an earlier paper, Thompson, Whitaker, and Kosar ^ reported on some genetic relationships between certain species of the 9-chromosome and of the IT-chromosome group of the genus Lactuca. Whitaker and Thompson^ presented data on some cytological aspects of these same species. In the first of these papers mention was made of 2 of the 8-chromosome species, but no compatibility relationships were...

The Colorado River is contaminated with perchlorate concentrations of 1.5-8 microg/L, an anion linked to thyroid dysfunction. Over 90% of the lettuce (Lactuca sativa L.) consumed during the winter months in the United States is produced in the Lower Colorado River region. Studies were conducted in this region to survey the potential for lettuce perchlorate accumulation and estimate potential hu...

Lettuce (Lactuca sativa) seeds var. Grand Rapids could be maintained many weeks in the dark without germination. Following illumination with white light, a gradual increase in polyribosome population up to the time of germination was demonstrated by sucrose gradient centrifugation. Polysomes could not be detected in imbibed seeds maintained continuously in the dark. Thus, polysome formation and...

Allelopathy between Mucuna pruriens (velvet bean) and Lactuca sativa (lettuce) was studied under 3D-clinorotation. Growth of both roots and shoots of lettuce seedlings was suppressed by the presence of velvet bean. The degree of suppression was less on the clinostat compared to the normal static earth gravity. L-DOPA (L-3, 4-dihydroxyphenylalanine) is known to be a major substance in allelopath...

Anthocyanin content and the activities of polyphenol oxidase (PPO), peroxidase (POD) and phenylalanine ammonia-lyase (PAL) and their relationships were determined in the leaves of six lettuce (Lactuca sativa L.) cultivars, exposed for 6 weeks to alternating three different day/night temperatures. Anthocyanin content was found to be highest at 20/13°C, followed by 25/20°C and 30/25°C, showing ac...