Abstract
Abstract When propagated in vitro, explants receive all the nutrients needed for their growth, including carbohydrates, from the culture medium. However, it is not well understood how the type and concentration of carbohydrates can affect the functioning of the photosynthetic apparatus (particularly photosystem II) of these plants. The aim was to assess the morphophysiological responses of Billbergia zebrina plants in function of sources and concentrations of carbohydrates during in vitro culture. Side shoots of plants previously established in vitro were individualized and transferred to a culture medium containing fructose, glucose or sucrose in four concentrations (0, 15, 30 or 45 g L−1). After growth for 55 days, the chlorophyll a fluorescence transient, leaf anatomy and growth were analyzed. The concentration and type of carbohydrate employed during in vitro culture did not decrease the photosynthetic apparatus performance. However, concentrations above 30 g L−1 led to anatomical modifications, revealing some degree of stress suffered by the plants. When grown in concentrations of 15 and 30 g L−1, irrespective of the carbohydrate used, the plants presented greater stomatal density. The supplementation of the culture medium with monosaccharides caused alterations in the development of the xylem vessels, such as increased number and diameter, allowing adjustment to the microenvironmental conditions. The in vitro conditions influenced the photosynthetic and anatomical responses of plants. The concentration interval from 15 to 30 g L−1 sucrose had a better effect by not causing large changes in the performance of the photosynthetic apparatus and anatomy of plants.
Highlights
Micropropagation is the most common method used for large-scale cloning ornamental horticulture plant species (Kumari et al, 2017; Naidoo et al, 2017; Bezerra et al, 2019)
Chlorophyll a fluorescence transients The analysis of chlorophyll a fluorescence transients revealed physiological differences in the B. zebrina plants cultured with different types and concentrations of carbohydrates
The results show that the use of any type of carbohydrate in the in vitro culture medium is important to maintain the photosystem II (PSII) quantum yield, since there was a decrease of φP0 and φE0 or increase of φD0, even when using concentrations considered to be high, like 45 g L-1
Summary
Micropropagation is the most common method used for large-scale cloning ornamental horticulture plant species (Kumari et al, 2017; Naidoo et al, 2017; Bezerra et al, 2019). Among the ornamental species frequently micropropagated are bromeliads. The exchange of CO2 as happens in natural conditions is prevented, the relative humidity within the flasks is high and the luminosity is low (Eckstein et al, 2012). These characteristics generate low photosynthetic activity, one of the main factors limiting the efficiency of micropropagation (Ševčíková et al, 2019). Plants partially lose their autotrophism, i.e., they do not totally produce their own energy source, so they need an exogenous source of carbohydrates (Martins et al, 2019)
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