The Morphological Responses of Calendula officinalis L. “Radio” to the Foliar Application of Benzyladenine and Different Light Spectra

Abstract

Pot marigold is a valuable medicinal plant with great decorative value. Three combinations of light (white (W)—170 μmol m−2 s−1, white + blue (W+B)—230 μmol m−2 s−1, white + red (W+R)—230 μmol m−2 s−1) were used to analyse the influence of a diversified light spectrum on the morphological traits and flowering of Calendula officinalis L. “Radio”. The effect of foliar treatment of the plants with 6-benzyladenine (BA) at concentrations of 100, 150 and 200 mg dm−3 at all the light spectrum combinations was analysed. BA had negative influence on the earliness of florescence and delayed it even by more than 10 days. W+B light intensified the delay, whereas red light partly reduced it. The BA treatment had the greatest influence on the biometric traits of the plants at the initial period of their development. W+B light significantly inhibited the growth of the plants. A high share of red light in the spectrum positively affected the Fv/Fm value, the relative chlorophyll content and the percentage of dry matter in the plants. When the amount of blue or red light in the spectrum increased, it was possible to obtain specific biometric traits of Calendula without the BA treatment.