Effects of light spectrum and UV-A radiation on in vitro seed germination and seedlings of Massai grass (Panicum maximum cv. Massai)

Abstract

The objective of this study was to evaluate the effects of different visible light spectra and UV-A radiation on the germination and morphology of Massai grass (Panicum maximum cv. Massai) seedlings in vitro. Seeds of cv. Massai from the 2024/2025 harvest were used. The experiment was conducted in germination boxes maintained at 25 ºC for 17 days under different light sources: white, red, green, yellow, absence of light (black), and UV-A radiation. Germination was monitored daily by counting the number of germinated seeds, with a 16-hour photoperiod. At the end of the experiment, seedlings were collected and evaluated for shoot length, root length, and fresh and dry mass. Results showed that the highest germination rates occurred between days 2 and 4 under green, red, and white light spectra. The lowest germination rate was observed under UV-A, reaching a maximum of 42%. Regarding seedling morphology, yellow light provided the best results, enhancing shoot length, root length, and fresh mass. In conclusion, visible light spectra such as green, red, and white promote rapid germination in a shorter time, while the yellow spectrum (570–590 nm) optimizes seedling morphological development in Massai grass. UV-A radiation, however, exerts deleterious effects from germination through early seedling growth