Articles
THE ROLE OF LIGHT QUALITY IN THE FORCING OF TULIPS AND HYACINTHS AND IN THE PROPAGATION OF HYACINTH BULBS
Only small amounts of light are necessary for obtaining the proper appearance of the plants (photomorphogenesis). For this reason these bulbous flowers are often forced in rooms with poor penetration of daylight, supplemented with artificial light.
To study the effects of different wavelengths on the flower development tulips and hyacinths were forced in climate rooms under different light sources: white, red and blue fluorescent light.
In hyacinths blue light had the most positive effects on flower development: anthocyanin production was accelerated by a few days (especially in the purple coloured cultivars), when compared with the red light treatment.
Plants remained shorter and the spreading of the leaves was enhanced by blue light.
In tulips flower quality was enhanced by blue light as well.
Flower stalks were longer (without a loss firmness) and flower pigmentation was better under blue light, when compared to red light.
White light always gave intermediary results.
Hyacinth bulbs are usually propagated by the so-called scooping technique: after excision of the basal plate the bulbs are incubated at 25°C in the dark.
Dependent on the cultivar 30–50 young bulbs are formed at the wound surface of each bulb.
The main problem with this propagation technique is not the number of newly formed bulbs but their tendency to remain dormant, after planting (thus reducing the yield at harvest). In the present study scooped bulbs of the cv.
Viking (well-known for its dormant daughter bulbs) were incubated under different light conditions: in the dark, under red, white and blue fluorescent light.
Light treatment had strong effects on the appearance (pigmentation an differentiation), but not on the number of young bulbs.
The light treatments effectively prevented the young bulbs from becoming dormant, as appeared from the number of emerged leaves after planting.
The higher number of leaves resulted in an increase in the yield of new bulbs after the first growing season 30–40%.