Gas Exchange Rates and Sucrose Concentrations Affect Development in Microstumps of Eucalyptus urophylla Grown In Vitro

Abstract Micropropagation enables the efficient clonal propagation of plants, bringing advantages to the Eucalyptus plantlet process. Herein, the influence of gas exchange rates and sucrose concentrations on the development of microstumps of a Eucalyptus urophylla S. T. Blake clone for microcutting production was evaluated. The microstumps were cultured under three gas exchange systems using caps with membrane, caps without membrane or a combination of the above, and also supplemented with 0, 7, 15 and 30 g L-1 sucrose. Gas exchange and sucrose supplementation affected the development of microstumps in vitro and the survival of microcuttings ex vitro. Lower sucrose concentrations were necessary under higher gas exchange rate conditions to improve the development and production of microstumps. Higher survival rates of ex vitro microcuttings were also observed under higher gas exchange rate. Sucrose is important in the initial plant development, but it can be reduced after the culture is established, depending on the gas exchange rate used. Thus, our findings show that reducing sucrose and increasing the gas exchange rates are efficient strategies for establishing microstumps of the Eucalyptus urophylla clone maintained under an in vitro condition. Study Implications: Photoautotrophic micropropagation can promote significant growth of Eucalyptus, and in this system, environmental factors need to be adequately controlled. This study has revealed efficient combinations of sucrose concentrations and gas exchange systems that promote greater in vitro production and greater ex vitro survival of microcuttings. Plants grown under higher gas exchange conditions show better acclimatization with higher survival rate during the ex vitro stage and require lower sucrose concentration during in vitro cultivation. This approach is useful in enhancing micropropagation techniques and indicates its potential application for scaling up large culture vessels to aseptic culture rooms for closed microcutting production systems.