Search Results

You are looking at 1 - 7 of 7 items for

  • Author or Editor: William Waycott x
Clear All Modify Search
Author:

A series of experiments was undertaken to study daylength-mediated control of transition to flowering in lettuce (Lactuca sativa L.), a quantitative long-day plant. Several genotypes (cultivars, landraces, and mutant lines) were grown at different photoperiods, sometimes in combination with different temperatures, and measured for number of days to either a) bolting initiation (a detectable increase in the rate of stem elongation) or b) anthesis of the first flower (a standard measure of maturity in lettuce). Experiments were conducted in controlled or partially controlled environments. Results of these studies indicate the following: a) high temperature alone is not sufficient to induce the bolting response, whereas photoperiod is; b) there is a range of genetic responses to various daylengths among lettuce genotypes; c) one of the genes known to control bolting initiation, gene Z', exhibited reverse dominance in conjunction with the Early Flowering genes, depending on the length of day. The latter observation implies the genetic role of T needs further investigation, as it does not appear to operate by simple dominance alone.

Free access
Author:

A series of controlled environment experiments were undertaken to study the effect of daylength on the transition to flowering in lettuce (Lactuca sativa L.), a quantitative long-day plant. A wide range of domesticated and wild lettuces were grown at five different photoperiods (8, 10, 13, 16, and 20 hr day-1) and measured for the number of days to 5, 10, and 30 cm. The results showed that the transition to flowering in lettuce is controlled by at least three different genetic systems: 1) a modified long-day system, typified by the American crisphead group, 2) a long-day system to which many of the European butterhead lettuces belong, and 3) the early flowering system. The first group was typified by a perceived non-linear response to daylengths between 10 hr and 13 hr, the response taking roughly the same number of days to flower under both of these daylengths. The second group showed a linear respond to incremental changes in daylength, while the crispheads were linear between 8 hr and 10 hr, and between 13 hr and 20 hr. This second group is known to have the long day gene tag, which induces rapid bolting in cultivars during long days. Our results indicate the effect of tag was no more than this linear response, and support the use of crispheads as a source of resistance to premature flowering, or bolting, for some time. The third system, early flowering, was nearly a day-neutral system. The plants flowered with a minimal response to increasing daylengths. Efforts of establish the exact physiological point of transition to flowering will be presented.

Free access

Abstract

A commercially available small garden seeder was modified to improve the precision planting of uncoated lettuce seed. The modified seeder is light weight, is adapted to planting small quantity seed lots, can be rapidly cleaned of remnant seed, and is designed for research and home garden use. Acceptable single seeding of uncoated lettuce seeds in the laboratory averaged 41.5%. Acceptable single seedling emergence in the field averaged 36.8%, a 13.6% improvement in the existing efficiency over the small plot seeder currently used. Minor modifications could make this planter design adaptable to most small-seeded crops.

Open Access