The in vivo growth and development of micropropagated Elatior begonias (Begonia x hiemalis): I. Study on the effect of lighting and substrate

Abstract

Micropropagation is an efficient way to produce pathogen-free Elatior begonias. However, certain problems arise when these plants are used in commercial pot plant production. The plants grow too luxuriantly, the root collars remain thin and flowering is delayed. To investigate the impact of the growing method, an experiment with different sources of supplementary light and different substrates was arranged in spring 1987. The following Elatior begonia cultivars were studied: ’Afrodite’, ’Afrodite Special’,'Afrodite Rosa’, ’Mandela’, ’Barbara’, ’Connie’, ’Marja’ and ’Sirene’. Four different lamp types were used: high pressure sodium lamps (Airam SNaKd 330 W), high-pressure mercury lamps (Airam HgLX 400W), high-pressure metal halide lamps (Philips HPI/T 375 W) and, as a control treatment, incandescent lamps of 100W. The plants were potted in B2-peat (Sphagnum peat with moderate fertilization and medium sieving grade), B2-peat (3 parts) plus perlite (1 part) or B2-peat (2 parts) plus perlite (2 parts). The plants lighted with SNaKd or HgLX lamps were the highest, the broadest and the first to reach anthesis and the sale stage. The plants in the control group were the smallest and the last to reach anthesis and the sale stage. The effect of the substrate on the time required to reach anthesis and the sale stage was clear only in the cultivar ’Afrodite Special’; when potted in peat-perlite 2 + 2, its plants flowered 2 weeks later than in other substrate mixtures. The height and the width of the plants were not greatly affected by the substrate. None of the lamp types or substrates clearly increased the number of flower buds or the diameter of the root collar. The proportion of saleable plants varied with the cultivar, lighting and substrate. In most cultivars it was below 50 %. The chief factors reducing saleability were luxuriant growth, weak flowering and oblique growth habit.