The effects of bulb storage temperature, planting date and soil temperature on the growth and development of Narcissus bulb units

Abstract

SummaryThree experiments were set up with field-grown narcissus, starting in 1995, 1996 and 1997. Each crop was grown for two years. Treatments were designed to alter the temperatures to which the bulbs were exposed, and consisted of twelve combinations of two pre-planting storage temperatures (pre-cooling and no pre-cooling), two planting dates (early and late) and three straw mulch treatments (no mulch, early mulch and late mulch). Treatments were applied only in the first year of each experiment, but crops were sampled regularly over both years and separated into their component parts to measure the effects of treatments on the growth and development of bulb units. The data showed how, over the two-year cycle, changes occurred in the fresh weight of the bulb cluster, the daughter bulb unit and the terminal mother bulb unit, which succeeded the daughter bulb unit. The daughter bulb unit followed a classic sigmoid growth curve, eventually reaching a weight of up to 10.g. The growth and development of bulb components in year one influenced the number of flowers and bulb yield in year two, but had no effect on the timing of flowering in year two. Earlier and greater development of the terminal mother bulb unit in year one gave earlier flowering and a greater daughter bulb unit weight that year. This then resulted in earlier development of the terminal mother bulb unit in year two and more flowers and a greater bulb yield in that year. There were positive correlations between the numbers of flowers in year two and the weights of foliage, terminal mother bulb unit and bulb cluster at emergence, flower cropping and senescence in year one. There were also positive correlations between bulb yield in year two and the weight of the bulb cluster at emergence, flowering and senescence in year one. Canonical variate and multi-variate analyses of the bulb component data showed that in year one there were significant effects on plant components of planting date and pre-planting storage temperature, while in the second year all main effects were significant.