During in vitro multiplication of horticulture plant species, synthetic cytokinins such as 6-benzylaminopurine (BA) can affect the microshoot formation. Murashige and Skoog culture medium (MS) can also act as a morphogenetic response modulator. The aim was to analyze the effects of BA and a gradient of MS salts on the morphophysiological status of Billbergia zebrina microshoots. Plantlets were cultured with a gradient of MS salts (50%, 100%, 150%, or 200%) supplemented with two BA levels (0 or 13 μM). After 50 days of culture, stomatal parameters, contents of photosynthetic pigments, and chlorophyll fluorescence were assessed. Plantlets cultured in all media without BA presented a low budding rate. In contrast, plantlets cultured with BA showed 100% budding. With 13 μM BA, the leaves presented bigger stomata and wider opening. Plantlets cultured with BA had lower contents of photosynthetic pigments. MS treatments without BA supplementation did not show any change in the pigments’ ratios. Plantlets cultured with BA had lower activity of the water-splitting complex and signs of photoinhibition damage. This resulted in the reduced performance of the photosynthetic apparatus. BA exposure can ensure the inducement of adventitious microshoots. BA at the tested concentration can induce morphophysiological disorders, irrespective of MS salt concentration.
The use of plants that present clear physiological responses to heavy metals such as cadmium (Cd) can assist in environmental monitoring. The aim was to evaluate physiological responses of Cd in Alternanthera tenella plants in micro-controlled conditions and to assess the its tolerance level and bioindicator potential. Nodal segments of A. tenella were grown in flasks containing semi-solid MS medium supplemented with (0, 50, 100, and 150 μM Cd). The total fresh and dry weight of the plants, in addition to physiological analyses, were determined after 30 days of cultivation. Plants submitted to Cd showed a reduction in biomass and photosynthetic pigments content. The decline in the Chl a/b ratio indicated the deleterious effects of Cd, as evidenced by the decrease in the density of active reaction centers (RC/CSM). The levels of deterioration in the functionality or structural integrity of the thylakoid membranes (WL) and the activity of the oxygen evolution complex (WK) increased as a function of Cd concentrations. The decreases in photochemical and non-photochemical quenching (qP and qN, respectively) observed in plants exposed to Cd indicated photochemical dysfunctions. Additionally, the increase in the quantum yield of non-regulated energy dissipation (ΦNO) indicated the presence of photodamage. Plants had a low/intermediate TI level (≥21.7) in the analyzed concentration range. A. tenella plants can bioaccumulate high amounts of Cd. The level of physiological responses of A. tenella is dependent on the concentration of Cd, which makes the use of this species even more promising as a bioindicator for this metal.