THE EFFECT OF THE LIGHT COLOUR ON THE GROWTH AND FLOWERING OF NARCISSI UNDER LONG-DAY AND HIGH QUANTUM IRRADIANCE CONDITIONS

Anita Woźny¹, Małgorzata Zalewska^2
1 Department of Ornamental Plants and Vegetable Crops, Faculty of Agriculture and Biotechnology, University of Science and Technology, Bydgoszcz, Poland
² Department of Ornamental Plants and Vegetable Crops, University of Technology and Life Sciences in Bydgoszcz, Poland

ABSTRACT

Four narcissi varietes were forced in artificial light using fluorescent lamps emitting white, blue, red, yellow and green light. The photosynthetic flux density (PPFD) was 25 ľ·m^-2·s^-1, whereas the length of the day was 12 hours. The bulbs of all the studied varieties flowered worse under the red light conditions. It was also observed that the light of white and blue colours improved the stem stiffness of narcissi of ‘Ice Follies’, ‘Johann Strauss’ and ‘Unsurpassable’ varieties in relation to the red, yellow and green light.

Key words: narcissi, forcing under artificial light, light colour, photosynthetic photon flux density.

INTRODUCTION

Narcissi, belonging to ornamental bulb plants, have small demands for the light taking part in photosynthesis because most of the necessary nutrient elements are accumulated in the bulb. Like tulips, lilies and crocuses, they can be forced with the use of artificial sources of light, in storehouses which are not used in winter [6,7,8,12]. Results of many studies point out that the light quality may have an effect on the date of flowering and the habit of numerous plant species. Information can be found in literature on the inhibition of the growth of seedlings and sets of ornamental and vegetable plants under the effect of blue light [3,5,9,10,15]. Finding out the effect of light of a definite wavelength on the flowering and quality of narcissi would make it possible to shorten the production and limit the use of chemical growth retardants.

It was shown in earlier studies that he use of light of different colours and intensity of quantum irradiance of 12.5 µmol·m^-2·s^-1 for 6 hours per 24 hours had no effect on the flowering of narcissi and the number of gathered flowers [17]. At the same time it was observed that he bulbs forced under blue light gave shorter and more stiff stems.

The purpose of the experiment was to study whether the light of different colours and greater intensity of quantum irradiance used for 12 hours per 24 fours has a significant effect on the flowering and the quality of the forced narcissi.

MATERIALS AND METHODS

The research material of the experiment were four narcissi varieties: ‘Ice Follies’, ‘Johann Strauss’, ‘Yellow Sun’ and ‘Unsurpassable’. Before the start of forcing, the bulbs were cooled down dry for 10 weeks, at the temperature of +5°C. Next, they were planted in cuvettes with the dimensions of 30×24×6 cm, filled with high peat with pH 5.5-6.5. One experimental combination (light colour × variety) included 40 bulbs. Cuvettes with the bulbs were placed in 5 isolated shelves in a growth habit. The onions were forced under glow lamps by Phillips with the power of 36 W, which emitted the light of white (307-770 nm), blue (393-580 nm), red (540-760 nm), yellow (450-750 nm) and green (387-680 nm) colours. The spectal characteristics of the light sources used in the experiment are presented in Fig. 1.

The photosynthetic flux density (PPFD) was 25 µmol·m^-2·s^-1, while the length of the day was 12 hours. The air temperature during the first two weeks of the cultivation was kept at the level of 11°C, and next it was raised to 16°C. The temperature was lowered to 14°C at the stage of bud colouring. The relative humidity of the air was 70%. While calculating the length of the period of forcing, the use was made of the mean value weighed with the date when the plants achieved the stage of commercial maturity. It was determined by the beginning of the plants’ flowering, i.e. the moment when the flower buds were delicately half-open and well coloured. The stage of complete development of the flower buds was taken as full flowering. The cut flowers were submitted to estimation considering the following parameters: the stem length from the base of the bud to the top of the corolla scale, the diameter of the perianth, the diameter and length of the corolla scale and the length of the longest leaf of the plant. Besides, the fresh weight of the stem was estimated after the latter had been cut off from the bulb. In the studies the stem stiffness was estimated on the basis of the degree of their swerve from the vertical. Conventionally, very slender stems corresponded to grade 1, which referred to the swerve of 30°, slender ones – 2 (swerve of 20°), stiff – 3 (swerve of 10°) and very stiff ones – 4 (no swerve). The results were statistically analyzed by means of variance analysis, and the significance of differences was evaluated with the Newman-Keuls test. The proportion of plants with difference stiffness of the stems was compared by means of t-Student test for the structure indexes.

RESULTS

The effect of the light colour on the length of the period of forcing narcissi was observed only in ‘Ice Follies’ (Table 1).

The bulbs forced under the red light conditions flower later than those subjected to the effect of the blue, white and yellow light. It was found out that in all the studied varieties the number of the picked flowers was considerably reduced by the red light (Table 2).

On the other hand, no effect of one, chosen colour on the yielding of narcissi was observed. The most flowers of ‘Ice Follies’ and ‘Johann Strauss’ varieties were picked up from the bulbs forced under the blue light, in ‘Yellow Sun’ under the yellow and green light, and in ‘Unsurpassable’ under white and yellow. The light colour with the photosynthetic flux density of 25 µmol·m^-2·s^-1, applied for 12 hours per 24 hours had no effect on the length and the fresh weight of the stem (Table 3).

The effect of the light colour on the leaf length was observed only in ‘Yellow Sun’ variety (Table 3). Plants forced under the lamps emitting the green light had the leaves of the greatest length, while the bulbs submitted to the white light yielded the shortest leaves, but they did not differ from those obtained under the yellow light. Differences in the diameter of the perianth and the corolla scale caused by the effect of the light of different colours were found out only in ‘Unsurpassable’ variety (Table 4).

The bulbs forced under the yellow light formed a bigger perianth than under the blue light. Narcissi of this variety forced under the conditions of yellow and red light had a bigger corolla scale in comparison to the plants from under the blue light. The light of different colours, on the other hand, had no effect on the length of the corolla scale of the studied varieties. The experiment also showed that the white and blue lights significantly improved the stiffness of narcissi stems.

In the case of ‘Ice Follies’ variety, while comparing the proportion of plants with definite stiffness with the plants obtained under the white and blue light, a smaller number of narcissi of stiff stems was observed in the red, yellow and green light. In ‘Johann Strauss’ variety such a reaction was observed under the red light, while in ‘Unsurpassable’ under the red and yellow light (Table 5).

DISCUSSION

The information concerning the effect of light of different intensities on the flowering and quality of ornamental bulbous plants points to a clear relation of the reaction with the species as well as the intensity and quality of the light used. In the experiment the effect of the light colour on the date of flowering was found out only in ‘Ice Follies’, which flowered the latest under the red light conditions. WoŸny and Jerzy [16] showed that the red colour light and the quantum irradiance intensity within the range of PAR of 12.5 and 25.0 µmol·m^-2·s^-1 applied, respectively, for 6 and 12 hours per 24 hours shortens the period of forcing the tulips. Tonecki [14] also claims that tulips lit with the red light in a glasshouse flower earlier. On the other hand, Suh [13] – while forcing tulips under the conditions of the light of red, far red, orange, blue and darkness – did not observe any effect on the kind of light on the date of flowering.

The onions of the examined narcissi varieties submitted to the effect of red light produced the fewest flowers. It was shown in the previous studies that the light of different colours and the intensity of quantum irradiance of 12.5 µmol·m^-2·s^-1 applied for 6 hours per day and night did not affect the number of the gathered narcissi flowers [17]. Increasing the intensity of quantum radiance to the level of 25 µmol·m^-2·s^-1 and lengthening the day to 12 hours could have caused the reaction to different light quality. Reports from literature point to worse flowering of plants submitted to the effect of red light resulting from the increased phenomenon of paperness [2,16] and greater productivity of ethylene, which has a negative effect on the bulbs [11].

It was observed that different kinds of light had little influence on the quality of the evaluated narcissi varieties. If changes did occur, then they concerned only singular varieties and had a multi-directional character. That made it impossible to indicate the light that had the most positive effect on the length, weight and size of flowers. At the same time, significant differences were indicated in the reaction of particular varieties, which may result from the fact that they belong to different groups. WoŸny and Jerzy [17] showed that narcissi of ‘Johann Strauss’ and ‘Yellow Sun’ varieties forced under blue light with the intensity of quantum radiance of 12.5 µmol·m^-2·s^-1 and a 6-hour-long photoperiod were shorter than those picked up from under red light. In Suh’s studies [13], the length of the first internod of tulips forced in blue light and in darkness was bigger in comparison to the control and the orange light. On the other hand, the red light stimulated elongation of the last internod. Bach et al. [1] observed that tulips of ‘Oxford’ variety were the lightest when grown in the blue light, but their weight was similar to the weight of plants obtained in the red light.

The present experiment observed considerable improvement of the stem stiffness when the narcissi were forced under the white and blue light. Gude and Dijkema [4] – while forcing tulips and hyacinths – obtained the most stiff stems in the conditions of the blue light. Hence, forcing the bulbs in the blue light may reduce the application of growth regulators in the case of strongly growing varieties.

CONCLUSIONS

1. Red light with the intensity of quantum irradiance within the range of photosynthetically active radiance of 25 µmol·m^-2·s^-1 and applied for the period of 12 hours per day and night delays the flowering of narcissi of ‘Ice Follies’ variety.

2. The bulbs of narcissi of ‘Ice Follies’, ‘Johann Strauss’, ‘Yellow Sun’ and ‘Unsurpassable’ varieties flower worse when subjected to the effect of the red light.

3. The studied narcissi varieties present different reactions to the light of definite spectral composition. The different reaction in reference to the quality of the flowers may result from the fact that they belong to different variety groups.

4. Narcissi of ‘Ice Follies’, ‘Johann Strauss’ and ‘Unsurpassable’ varieties subjected to the effect of white and blue light are characterized by greater stem stiffness as compared to the plants forced under the red, yellow and green light.

REFERENCES

1. Bach A., Włodarczyk Z., Œwiderski A., 1997. Wpływ rodzaju œwiatła na wzrost i rozwój tulipanów pędzonych w szklarni [The effect of the kind of light on the growth and development of tulips forced in a glasshouse]. Zesz. Probl. Post. Nauk Roln. 449, 23-30 [in Polish].

2. Bach A., Włodarczyk Z., Œwiderski A., 1998. Wpływ rodzaju doœwietlania na wzrost i rozwój tulipanów pędzonych bez dostępu œwiatła naturalnego [The effect of the kind of irradiation on the growth and development of tulips forced without the access of natural light]. Ogólnopolska Konferencja “Ogrodnictwo ozdobne przełomu wieków”. Kraków, 14-15 maja. Mat. konf., 27 [in Polish].

3. Decoteau D. R., Kasperbauer M. J., Daniels D. D., Hunt P. G., 1988. Plastic mulch color effects on reflected light and tomato plant growth. Sci. Hort., 34, 169-175.

4. Gude H., Dijkema M., 1992. The role of light quality in the forcing of tulips and hyacinthus and in the propagation of hyacinth bulbs. Acta Hort., 305, 111-112.

5. Hunt P. G., Kasperbauer M. J., Matheny T. A., 1989. Soybean seedling growth responses to light reflected from different colored soil surfaces. Crop Sci., 29, 130-133.

6. Jerzy M., 1980., Artificial light as substitute for daylight in forcing tulips. Acta Horticulturae, 109, 105-110.

7. Jerzy M., Krause J., 1980. Two factors controlling growth and flowering of forced lilies ‘Enchantment’: light intensity and mechanical stress. Acta Hort., 109, 111-115.

8. Jerzy M., Krause J., 1981. Crocus – forcing in artificial light. Sci. Hort., 15, 263-266.

9. Maas F. M., Bakx E. J., 1997. Growth and flower development in roses as affected by light. Acta Hort., 418, 127-134.

10. McMahon M. J., Kelly J. W., Decoteau D. R., 1991. Growth of Dendranthema × grandiflorum (Ramat.) Kitamura under various spectral filters. J. Am. Soc. Hort. Sci., 116, 950-954.

11. Michalczuk B., Rudnicki R. M., Moe R., 1992. The effect of light quality on ethylene biosyntesis in leaves and petals of Alstroemeria plant. Acta Hort., 325, 313-318.

12. Piszczek P., Jerzy M., Zalewska M., 1996. Wzrost i kwitnienie narcyzów w warunkach naturalnego i sztucznego oœwietlenia [Growth and flowering of narcissi in the conditions of natural and artificial light]. Zesz. Nauk. ATR Bydgoszcz, Rolnictwo, 39, 25-32 [in Polish].

13. Suh J. K., 1997. Stem elongation and flowering response of Tulipa cultivars as influenced by bulb cooling, growth regulators and light quality. Acta Hort., 430, 101-106.

14. Tonecki J., 1998. Wykorzystanie systemu fitochromowego do sterowania procesami wzrostu i kwitnienia roœlin [Using a phytochrom system to steer the processes of growth and flowering of plants]. Ogólnopolska Konferencja “Ogrodnictwo ozdobne przełomu wieków”. Kraków, 14-15 maja. Mat. konf., 92 [in Polish].

15. Warpeha K. M. F., Kaufman L. S., 1989. Blue-light regulation of epicotyl elongation in Pisum sativum. Plant Physiology, 89, 544-548.

16. WoŸny A., Jerzy M., 2004. Wpływ barwy œwiatła na zimowe kwitnienie tulipana [The effect of the light colour on the winter flowering of tulip]. Bydg. Tow. Nauk. BTN, Seria B, 52, 375-381 [in Polish].

17. WoŸny A., Jerzy M., 2007. Effect of light wavelength on growth and flowering of narcissi forced under short-day and low quantum irradiance conditions. J. Hort. Sci. Biot., 82 (6) 924-928.

Accepted for print: 15.04.2008

Responses to this article, comments are invited and should be submitted within three months of the publication of the article. If accepted for publication, they will be published in the chapter headed 'Discussions' and hyperlinked to the article.