Avocado shoot culture, plantlet development and net CO2 assimilation in an ambient and CO2 enhanced environment

Summary  The proliferation and survival of avocado nodal cultures of juvenile origin were affected by the form and concentration of nitrogen. Optimum growth was achieved on modified Murashige and Skoog medium containing 67% KNO₃ and 33% NH₄NO₃ with total N of 40 mM supplemented with 100 mg l⁻¹ myo-inositol, 1 mg l⁻¹ thiamine HCl, 30 g l⁻¹ sucrose, and 4.44 μM BA with a 16-h photoperiod (120–150 μmol m⁻² s⁻¹). Proliferating shoots and plantlets were photosynthetically active. Better shoot growth and accumulation of higher biomass occurred in a CO₂-enriched environment than under ambient CO₂ conditions. CO₂ assimilation efficiency, however, was higher under the latter conditions than in a CO₂-enhanced environment, e.g., 31±7 and 17±2 μmol CO₂ m⁻² s⁻¹, respectively. The net CO₂ assimilation rates of in vitro grown plantlets were comparable to those of seedlings ex vitro.