Performance characteristics of Lesquerella fendleri as influenced by plant density.

Abstract

Lesquerella fendleri has been targeted for domestication to provide the U.S. chemical industry with a domestic source of hydroxy fatty acids. Field studies of density, harvest dates and shadehouse investigations of water stress were initiated to determine the response of seed and oil yields in Lesquerella. Field thinned plants were grown at 250,000; 500,000; 750,000; 1,000,000; and their unthinned controls of 1,658,000 plants/ha in 1992-1993 and 1,500,000 plants/ha in 1993-94. Increasing density in 1992-93 resulted in reduction of vegetative growth, and a decline in harvest index through decreases in the number of branches and siliques/branch. Increasing density also reduced seed number/silique in the control and the 750,000 plants/ha treatments, without effecting other seed characteristics. Density increased taproot length and height in the 750,000 plants/ha treatments. Greatest seed yields were obtained at 750,000 and 1,000,000 plants/ha and the lowest in the extreme density treatments. Seeds produced in the lowest density also had lower oil content. Second year data at final harvest, 264 days after sowing (DAS), did not show differences in seed and oil yields among treatments. However, developing seeds did show differences in oil yield, due to variations in timing of maximum oil accumulation. The 750,000 plants/ha treatment reached peak oil deposition around 203 DAS, followed by 1,500,000 and the 500,000 plants/ha treatments at 229 DAS, and finally the 1,000,000 and 250,000 plants/ha treatments at 243 DAS. The earliest oil formed was devoid of auricolic acid in the 750,000 and 1,000,000 plants/ha treatments, and was dominated by stearic, oleic, linoleic, and linolenic acids. Later depositions were mostly lesquerolic acid. At normal harvest, 264 DAS, the 750,000 plants/ha treatment accumulated greater proportion of auricolic acid. Early termination of irrigation at the beginning of flowering, and at one, two, and three weeks after flower initiation decreased height, taproot length and the number of branches/plant. Termination of irrigation during the first week of flowering reduced flowering and silique production. Water deficits reduced seed yield through abortion of siliques and declining seed weight. Irrigation through harvest did not demonstrate higher water use efficiency than termination of watering two weeks after flowering.