Sources and concentrations of silicon modulate the physiological and anatomical responses of Aechmea blanchetiana (Bromeliaceae) during in vitro culture

Abstract

The use of silicon (Si) has been shown to be a good alternative to improve the growth and content of photosynthetic pigments of plants propagated in vitro. So far, it is not well understood how the sources and concentrations of Si can affect the root and leaf anatomy as well as the functioning of the photosynthetic apparatus of these plants. The aim was to assess the physiological and anatomical responses of Aechmea blanchetiana plants in function of sources and concentrations of Si during in vitro culture. Side shoots of plants previously established in vitro were excised and transferred to a culture medium containing CaSiO3 or Na2SiO3 in four concentrations (0, 7, 14 or 21 µM). After culture for 90 days, the chlorophyll a fluorescence transient, root and leaf anatomy, contents of photosynthetic pigments and mineral nutrients as well as growth were analyzed. Plants grown in medium supplemented with Na2SiO3 presented characteristics of salt stress, such as smaller stomata, higher potassium content and lower number of active reaction centers (RC/CSM). On the other hand, plants cultured with 7 and 14 µM CaSiO3 had an increase in photosynthetic pigment content and performance of photosynthetic apparatus, verified by the performance indexes (PI(ABS) and PI(TOTAL)). The employment of concentrations equal to or higher than 21 µM Si, independent of Si source, caused toxicity symptoms in the plants. The use of CaSiO3 had a positive effect on the concentration interval between 7 and 14 µM by improving physiological and anatomical quality of A. blanchetiana plants. Silicon source and concentration can affect the physiological responses of Aechmea blanchetiana during in vitro culture. This study highlights that CaSiO3 increases the photosynthetic pigment content and photosynthetic apparatus performance.