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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.

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In vitro culture conditions have a major impact on the physiology and anatomy of micropropagated plants. Sucrose plays a very important role in micropropagation protocols, and is frequently employed during in vitro culture. However, it may induce disorders that negatively interfere with plant growth and development, such as a low photosynthetic rates. The aim of this study was to analyze the impacts of in vitro conditions on the anatomy and photosynthetic performance of Aechmea blanchetiana (Baker) L.B. Sm. Plants previously grown in vitro were transferred to culture media containing 0, 15, 30, or 45 g L −1 sucrose. Two different culture container sealing systems were tested: lids with a filter (permitted gas exchange), and with a PVC-covered filter (blocking fluent gas exchange). Plants grown with exogenous sucrose displayed anatomical traits that could decrease mineral and carbohydrate uptake from the medium. Plants cultured under photoautotrophic conditions had a thinner exodermis and the highest number of metaxylem vessels in the roots. This positively impacted the plant growth and physiological status. Sucrose induced plants with photosystem II (PS II) disorders, such as a lower number of active reaction centers. Under photoautotrophic conditions, there was an increase in absorbed energy flux per cross section (ABS/CSm), and energy transport flux (ETo/CSm), followed by a decrease in the energy dissipation flux (DIo/CSm). This indicated a high PS II efficiency, according to the performance index (PI (ABS) ). The use of sucrose can induce physiological disorders in A. blanchetiana plants during in vitro propagation. Photoautotrophic conditions induce plants without anatomical disorders, and positively influence PS II efficiency.

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