Ryvässipulin (Allium cepa L. v. Solaninum alef.) idätyksen vaikutuksesta kukintojen kehittymiseen ja sipulin versomiseen varastossa

Authors

• Klaus Aura Kasvitautien tutkimuslaitos, Tikkurila

DOI: https://doi.org/10.23986/afsci.71464

Abstract

Cold weather at the beginning of the period of growth often causes the development of the flower stalk in multiplier onion though the sets have been kept in a warm place (18—24°C) during the previous months of storage (cf. 2). At the beginning of the period of growth in 1957 it was very chilly, resulting in the onion in general flowering plentifully over almost the whole country. Experiments were made at the Department of Plant Pathology, Agricultural Research Centre, in 1957, to determine whether the flowering of the onions as a result of spring cold could be hindered by allowing the sets to germinate in the spring before setting. The average diameter of the sets was about 4 cms. The onions used in the experiment were stored in a temperature of 20—24°C. Germination took place in an unheated greenhouse, the onions being set in a damp bed of moss for 4, 8 and 13 days. During germination the 24-hourly maximum and minimum temperatures in the greenhouse were on the average 30.0°C and 8.9°C. The mean temperature of the total germination period was about 19°C. Cold weather prevailed after setting the onions (on 24.5). During the first week the 24-hourly minimum temperature at ground level was 0.6°C and the maximum 11.8°C. The mean temperature during this week was 7.2°C. The following week was also cold. During the period of growth it was ascertained that ungerminated onions developed a great number of flower stalks (almost 5000 stalks per are). In the onions which had germinated for 4 days the number of flower stalks was less, being 340 stalks per are. Germination for 8 and 13 days completely hindered the development of flower stalks (Table 1, Fig. 1). It thus appears that a subsequent comparatively short and warm period after setting is sufficient to hinder the onion from flowering, even if the weather becomes cold later on. In 1955 and 1956 the onion variety (Hytti) used in the experiments did not flower at all, though the minimum night temperatures at ground level were low after setting. On the other hand, the maximum and average 24-hourly temperatures were high compared to the corresponding values in 1957, particularly during the first week (Table 2). Thus it is probable that sufficiently high temperatures during the daytime can prevent the onion from flowering by compensating the effect of low night temperatures. The presence of a large number of flower stalks had a great effect on the yield of the onion (Table 1). The yield from ungerminated onions was only a third of that from germinated onions. Further, of the yield from the ungerminated plants almost half (49.5 %) was wasted because of flower stalks. The yield from onions which had germinated for 4 days was almost as big as that from the onions with longer germination periods, in spite of the 340 flower stalks per are. Boswell (1) has shown that the actual time of maturity is significant with regard to the storage of the onion, so that onions which have maturited at a later date sprout more during storage than those which have maturited earlier. In the storage period 1956—57 experiments carried out at the Department of Plant Pathology with onions that had been allowed to germinate for two weeks before setting and with ungerminated onions, showed that the germinated onions did not sprout so much while in storage as the ungerminated onions did (Table 3). According to observations made during the period of growth, the germinated plants maturited almost three weeks earlier than the ungerminated plants.