Original Paper Environ. Control Biol., 44 (1), 51-58, 2006 Effects of Seedling Container Size and Nursing Period on the Growth, Flowering, and Yield of Cut Flowers in Snapdragons (Antirrhinum majus L.) Zentaro INABA Shizuoka Agricultural Experiment Station, Minamiizu Branch, Minamiizu-cho, Shizuoka 415-0302, Japan (Received October 20, 2005) We investigated the effects of the size of seedling container used in the nursery (deep or shallow types) and of the nursing period (25, 30, or 35 days) on the growth and flowering of snapdragon (Antirrhinum majus L.) cv. emaryland Pink' and elight Pink Butterfly II'. Snapdragons were seeded in July and pinched in September. We compared the results with those of the conventional method (temporary planting) for raising seedlings. Plant growth and subsequent yields of cut flowers increased in the deep containers. In seedlings raised for 35 days, plant height and the number of nodes decreased at the time of pinching, and the number of days from pinching to flowering of the second-node shoots increased. Flowering of the second-node shoots of plants with non-temporary planting occurred earlier than in the conventional method, and the yield of cut flowers was greater. To nurse the seedlings without temporary planting, planting within 30 days seems to be suitable regardless of the seedling containers that are used. Keywords: pinching, seedling method, temporary planting, transplanting INTRODUCTION Pinching cultivation is the conventional method used for snapdragon (Antirrhinum majus L.) production in warm districts of Japan (Inaba, 1994). However, non-pinching cultivation is carried out in the U.S.A. Snapdragons have been classified into four groups based on their temperature and photoperiod responses. Groups in which the earliness of flowering differs have different, seasonally classified flowering times (Rogers, 1992; Con and Laughner, 1998). In groups and cultivars that have been selected for pinching cultivation, the flowers are harvested from autumn to spring, over a period of about 5 to 7 months in Japan (Inaba, 2001). Production of snapdragons was carried out in open-field culture along the coast of Japan soon after World War II. Afterwards, production was increased by means of cultivation under protective structures such as glasshouses (Inaba, 1994, 2001; Keida, 1994). At production centers such as those used in Shizuoka prefecture, the seedlings are planted temporarily after cotyledon development, then are pinched and transplanted to complete the rest of their development (the gconventional method h)(inaba, 1994; Hosoya, 1994; Keida,1994). In recent years, some production centers have adopted a non-temporary planting system in which seedlings are raised in containers filled with commercial potting soil and are not transplanted (Abe and Sasaki, 1994; Inaba, 2001). At Corresponding author : Zentaro Inaba, fax: +81-558-62-0129, e-mail: z-inaba@agri-exp.pref.shizuoka.jp Vol. 44, No. 1 (2006) (51) 51
Z. INABA Japanese production centers, seedlings are generally raised by the growers. Nursing seedlings without temporary planting seems to be more economical than the conventional method. Raising seedlings for pinching cultivation is carried out during the high-temperature period of the summer. At the production centers where growers become old, non-temporary planting seems to offer some advantages. In our research, flowering of the primary shoots from the second node was accelerated and the yield of cut flowers was increased by non-temporary planting. These results suggested that there was a difference in the growth response after seedlings were planted continuously (Inaba and Ohshiro, 2004). Inaba (1994) reported that when planting is delayed during the pinching cultivation used in the conventional method, flowering is also delayed. Goto (2002) reported that the flowering of snapdragons in non-pinching cultivation was delayed by both extending the time for raising the seedlings and by decreasing the volume of the soil plugs that contain the seedlings. These findings suggested that differences in transplant quality affect subsequent flowering in pinching cultivation of snapdragon. However, the condition of the seedlings in pinching cultivation has not been studied. The purpose of the present study was to develop a more efficient cropping system for pinching cultivation of snapdragons in warm parts of Japan. I examined the effects of the seedling container and the nursing period on flowering, and on the yield and quality of cut flowers, in the emaryland Pink' Group I cultivar (Corr and Laughner, 1998) and in the elight Pink Butterfly II' Group II cultivar (Inaba and Ohtsuka, 2002). MATERIALS AND METHODS I performed the experiment using a soil bed 80 cm in width oriented in a north-south direction inside a glass-covered greenhouse (148 m2) at the Shizuoka Agricultural Experiment Station's Minamiizu branch. I used the emaryland Pink' and `Light Pink Butterfly II' cultivars in the experiment. Two types of containers that are commonly used in snapdragon production in warm areas of Japan were used in the experiment. The deep type of containers (with a length of 33 cm, width of 47 cm, and depth of 7 cm) are commonly used for sowing and cutting of ornamental plants. In contrast, the shallow type of container (with a length of 28 cm, width of 58 cm, and depth of 3 cm) are more commonly used for sowing of rice. The volume of the growing medium in the deep containers is about two times grater than that in the shallow containers. Three nursing durations were used: 25, 30, and 35 days (25-, 30- and 35-d). The control treatment was a group of seedlings grown using the conventional method. Sample size was about 300 seeds sown in each type of container filled with commercial planting soil (Yosaku N-150, Chisso-Asahi Fertilizer Co., Ltd., Japan) on 31 July 2001. Seeds in the 25-, 30-, and 35-d nursing treatments were planted on 25 August, 30 August, and 4 September, respectively. The plants were pinched above the second node on 10 September. In the conventional method (with temporary planting), about 300 seeds were sown in the deep type container on 31 July 2001, and seedlings were planted temporarily in a floor on 15 August once the cotyledons had developed. The temporary planted floor was filled with disinfected soil that had been mixed with mountain soil and bark compost in a ratio of 2:1, and supplied with coated fertilizer (Long 424 180-day type, Chisso-Asahi Fertilizer Co., Ltd., Japan) at 20 g per m2. The seedlings were pinched on 10 September and planted on 17 September. After sowing, the containers were placed in the greenhouse and irrigated using misting equipment for 14 days. Mist spraying was stopped when true leaves were observed. The seedlings were then irrigated according to the dryness. Planting density was 6 plants per row (Yonemura, 1990). Rows were 0.8 m long and the 52 (52) Environ. Control Biol.
NURSERY CULTURE AND SNAPDRAGON YIELD distance between rows was 0.2 m. The fertilizer was applied to the soil bed before planting and start harvesting. The amounts of N, P205, and K20 were 1.4, 1.6 and 1.8 kg a-1, respectively. The night temperature was set at 11 Ž from 25 November. The yield and quality of cut flowers were examined from the start of harvesting to 31 March 2002. Daytime temperature inside the greenhouse was managed by opening the side windows from 09:00 to 16:00 if the outside temperature did not fall below 11 Ž B For each treatment, 18 plants were used and the experiment was replicated twice. The primary and secondary lateral shoots generated after the pinching were not arranged. The flowering date was defined as the date when four florets in a spike had opened. All flowering shoots were harvested above the lowest node above the point of branching on 31 March. From the time of pinching until flowering, the length of the cut flowers and the number of nodes generated at different positions were scored. The marketable value of the cut flowers was judged according to the standards that were applied in the flower-producing area. Figure 1 shows the shoots that were generated from different nodal positions. Flowering in both cultivars occurred in the following order: first, on the primary lateral shoots from the second node after pinching (II-1st branch); second, on lateral shoots from the first node and the cotyledon node, in which flowers bloomed almost simultaneously (I branch); and third, on secondary lateral shoots from the second node after the first harvest (II-2nd branch). RESULTS Air temperature in the greenhouse during nursing ranged between a minimum of around 25 Ž and a maximum of around 35 Ž until 15 August, then decreased slowly thereafter (Fig. 2). Plant height and the number of nodes at the time planting were significantly smaller in the Fig. 1 Diagram showing the shoot generated from different nodal positions. Fig. 2 The temperature of the greenhouse during nursing of seedling periods. Vol. 44, No. 1 (2006) (53)53
Z. INABA shallow containers than in the deep containers for both cultivars (Table 1). In particular, 30 days after sowing in the shallow containers, plant height and the number of nodes in emaryland Pink' were 7.0 cm and 2.0, respectively, whereas those in elight Pink Butterfly II' were 5.4 cm and 2.0, respectively. Growth almost stopped in the shallow containers in the 30-d treatment. Root length only differed significantly among treatments for emaryland Pink', for which root length increased significantly with increasing nursing period (Table 1). The plant height and number of nodes at pinching decreased as nursing period increased in both types of container for emaryland Pink' and the number of nodes decreased in the shallow containers for elight Pink Butterfly II' (Table 2). For seedlings in shallow containers in the 35-d treatment, plant height and the number of nodes in emaryland Pink' were 7.5 cm and 3.0, respectively, versus 5.9 cm and 2.6, respectively, in elight Pink Butterfly II'. These values were less than those in the conventional method, and the difference was significant for all comparisons except the plant height of emaryland Pink' (Table 2). In emaryland Pink', the time from pinching to flowering was affected by the nursing period (Table 3). The time to flowering (II-1st branch, days) in both container types in the 35-d treatment was significantly longer than in the 25- and 30-d treatments, and all these times were significantly Table 1 Effects of seedling container size and nursing period on plant height, node number and root length at the planting in snapdragons. Plants were sown on July 31, 2001. Nursing period for 25, 30 and 35 days were planted at August 25, August 30 and September 4, respectively. Table 2 Effects of seedling container size and nursing period on plant height and node number at the pinching in snapdragons. Plants were sown on July 31, 2001 and pinched on September 10 (Same as Tables 3, 4 and 5). Seedling were transplanted temporary on August 15 (Same as Tables 3, 4 and 5). *** Significant at P 0.001. Different letters within a column indicate significances at the 5% level by Ryan's multiple range test (Same as Tables 3, 4 and 6). 54 (54) Environ. Control Biol.
NURSERY CULTURE AND SNAPDRAGON YIELD Table 3 Effects of seedling container size and nursing period on number of days from the pinching to flnwerino of the branches from different positions in snapdragons. shorter than in the control. The time from pinching to flowering of the I branch in the 35-d treatment was significantly shorter than in all other nursing lengths in deep containers, but not significantly different in shallow containers. In `Light Pink Butterfly II', the time to flowering of the II- 1st branch was significantly longer in the control than in all other treatments except the 35-d nursing treatment in shallow containers. The time to flowering (II-1st branch) in the conventional method was the longest of all treatments in both cultivars, though the difference was not significant for the 35-d nursing treatment in shallow containers (Table 3). The yield of cut flowers in emaryland Pink' (Table 4) was not affected by container size or nursing period. However, in elight Pink Butterfly II', the yield of cut flowers on the II-2nd branch and the total number of cut flowers in the deep containers tended to be greater than those in the shallow containers. The yield of cut flowers in the non-temporary planting was greater than that in the conventional method in most treatments, regardless of container size and nursing period, though there were exceptions (Table 4). The cut flowers produced by the 35-d treatment in emaryland Pink' were longer than those in the shorter nursing treatments in both container types, but the difference was not significant, and the length in the control treatment was significantly longer than in any treatment except the 35-d shallow containers. In elight Pink Butterfly II', the length of the cut flowers differed among treatments for both the II-1st branch and the I branch. In the conventional (control) treatment, cut flowers of the II-1st branch in `Maryland Pink' and of the II-1st and I branches in elight Pink Butterfly II' were relatively long compared with the nursing treatments (Table 5). The quality of marketable flowers increased with increasing yield of cut flowers (data not shown). DISCUSSION Plant height and the number of nodes at planting were greater in the deep containers than in the shallow containers. Similarly, plant height and the number of nodes at pinching decreased as the nursing period increased. This change was remarkable in the shallow containers. Plant growth is influenced by restriction of the root area caused by the container size or the number of plants per container (Whipker et al., 2003). Since the same number of seeds were sown in both container types, the capacity of the deep containers available for each seedling was about twice that provided by the shallow containers. Therefore, the difference in growth between the deep and shallow containers can probably be attributed to the different container sizes. Flowering times of the II-1st branch and the I branch in emaryland Pink' were affected by the Vol. 44, No. 1 (2006) (55)55
Z. INABATable Effects of seedling container size and nursing period on yields of cut flowers of the branches from di 56(56) Environ. Control Biol.
NURSERY CULTURE AND SNAPDRAGON YIELD Table 5 Effects of seedling container size and nursing period on the length of cut flower stems generated from different positions in snapdragons. nursing period, whereas those of the II-1st branch in elight Pink Butterfly II' were affected by shallow containers in the 35-d treatment. These results indicate that the factors that most strongly affect flowering time differ between the cultivars. No effect of container size and nursing period on the yield of cut flowers was found in the non-temporary planting of emaryland Pink'. In elight Pink Butterfly II', the yield of the II-2nd branch and the yield per plant were relatively low in the shallow containers. Thus, the yield of cut flowers decreased with decreasing container size and with increasing nursing period. emaryland Pink', which is in group I (Cory and Laughner, 1998), and elight Pink Butterfly II', which is in group II (Inaba and Ohtsuka, 2002), have different earliness of flowering and different temperature response (Inaba and Horiuchi, 2003; Inaba and Ohshiro, 2003). The yield of cut flowers in elight Pink Butterfly II' was greater than that in emaryland Pink'. Thus, the yield of cut flowers in pinching cultivation of snapdragon was affected not only by the earliness of the cultivars but also by the generation of the branch from each plant part. The length of cut flowers of emaryland Pink' and elight Pink Butterfly II' from the II-1st branch in the shallow containers of the 35-d treatment and in the conventional method were relatively long. However, there was no clear trend for the I branches. The length of cut flowers of snapdragon are affected by night temperature and day length (Inaba and Horiuchi, 2003). In the II -1st branch, the flowering date in the 35-d treatment and the conventional method tended to be later than in the other treatments. Thus, the increase in flower length is likely to be attributable to the extension of the period of vegetative growth. As described above, flowering time and flower length were affected by the nursing period in e Maryland Pink', whereas in elight Pink Butterfly II', yield was affected by container size, and flowering time and flower length were affected by nursing period. The yield of cut flowers is very important to ensure the profitability of a growing operation. Thus, to produce elight Pink Butterfly II', attention should be paid to both the container size and the nursing period. In many regions of Japan where snapdragons are grown, the growers raise seedlings using deep or shallow containers (Abe and Sasaki, 1994; Hosoya, 1994; Inaba, 1994, 2001; Keida,1994). In some areas, plug seedlings are also used (Fuse, 1994). Goto (2002) reported that flowering was delayed with increasing period to nursing seedling using plug seedlings in non-pinching cultivation of cv. emangetsu'. In the present study, there was little difference in flowering time of the II-1st branch between the 25- and 30-d treatments in pinching cultivation. However, flowering time of the II-1st branch in the 35-d treatment tended to be later than in the 25- and 30 -d treatments. It seems that the period of vegetative growth of the II-1st branch after pinching is extended by increasing the period for nursing seedling in pinching cultivation of snapdragon Vol. 44, No. 1 (2006). However, the (57)57
Z. INABA cultivation conditions reported by Goto (2002) differ from those used in warm parts of Japan. Thus, further studies will be required on the pinching cultivation of snapdragons using plug seedlings. Non-temporary planting of seedlings tended to accelerate flowering of the II-1st branch and increased the yield per plant compared with the conventional method. The potential number of marketable cut flowers would thus increase, as the yield of cut flowers increased during nontemporary planting. Therefore, non-temporary planting appears to be an efficient method to improve the productivity of growing operations. In the present study, the growth, flowering, and yield in pinching cultivation of snapdragons were affected by container size and nursing period for about one month after sowing. The deep containers improved growth and yield compared with the shallow containers. When seedlings were nursed for 25- and 30-d, flowering time, yield and length of the cut flowers were similar. However, the yield of cut flowers in the 35-d nursing treatment tended to be less than those in the 25- or 30-d treatments according to the container size or cultivar. To grow seedlings without temporary planting, a 30-d nursing treatment appears to be suitable regardless of the container type. valuable I am grateful to Dr. Kazuo Ichimura, National Institute of Floricultural Sciences, NARO, Japan, for his advice. REFERENCES Abe, H., Sasaki, T. 1994. Snapdragon. In gnougyou Gijyutsutaikei Kakihen h, Vol. 8. Noubunkyo, Tokyo, p 81-87. Corr, B., Laughner, L. 1998. Antirrhinum. In gball Redbook h, Ed. 16, Ball Publishing, Illinois, p 356-367. Fuse, S. 1994. Snapdragon. In gnougyou Gijyutsutaikei Kakihen h, Vol. 8. Noubunkyo, Tokyo, p 89-94. Goto, T. 2002. Development of auto irrigation system for transplants based on the clarification of growth phase in floriculture cell transplants. PhD thesis. Kyoto Univ., Kyoto, pp 176. Hosoya, K. 1994. Snapdragon. In gnougyou Gijyutsutaikei Kakihen h, Vol. 8. Noubunkyo, Tokyo, p 95-100. Inaba, Z. 1994. Snapdragon. In gnougyou Gijyutsutaikei Kakihen h, Vol. 8. Noubunkyo, Tokyo, p 55-75. Inaba, Z. 2001. Snapdragon of Izu. In gshizuokaken Yasai Kaki Engeihattatsushi h, Shizuokaken Yasai Kaki Engeihattatsushi Hensan Iinkai, Shizuoka, p 332-333. Inaba, Z., Horiuchi, M. 2003. Effects of night temperatures and day length in the winter on the flowering, yields and quality of snapdragon (Antirrhinum majus L.). (Japanese text with English summary) Hort. Res. 2: 199-203. Inaba, Z., Ohshiro, M. 2003. Effects of starting time of the heating and night temperature setting in winter on the flowering and quality of snapdragons (Antirrhinum majus L.). (Japanese text with English summary) Hort. Res. 2: 303-306. Inaba, Z., Ohshiro, M. 2004. Effects of the nursing seedling method and winter night temperature on th e flowering, yields and quality of snapdragons (Antirrhinum majus L.). (Japanese text with English summary) Hort. Res. 3: 273-276. Inaba, Z., Ohtsuka, H. 2002. Effects of winter night temperature on the flowering of snapdragons (Antirrhinum majus L.).(Japanese text with English summary) Hort. Res. 1: 263-267. Keida, S. 1994. Snapdragon. In gnougyou Gijyutsutaikei Kakihen h, Vol. 8. Noubunkyo, Tokyo, p 101-105. Rogers, M. N. 1992. Snapdragons. In gintroduction to Floriculture h(ed. by Larson, R.A.), Ed. 2, Academic Press, San Diego, p 94-112. Whipker, B. E., Gibson, J. L., Cams, T. J., McCall, I., Konjoian, P. 2003. Growth regulators. In gball Redbook h, Ed. 17, Vol. 2. Ball Publishing, Illinois, p 85-112. Yonemura, K. 1990. Planting. In gcarnation Gekan h(ed. by Yonemura, K.), Seibundo Shinkosha, Tokyo, p 83-102. 58(58) Environ. Control Biol.