Avocado Shoot Culture, Plantlet Development and Net CO2Assimilation in an Ambient and CO2Enhanced Environment

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$67\% KNO_3$and 33% NH4NO 3with total N of 40 mM supplemented with$100 mg l^{-1}$myo-inositol,$1 mg l^{-1}$thiamine$HC1, 30 g l^{-1}$sucrose, and$4.44 \mu M BA$with a 16-h photoperiod$(120-150 \mu mol m^{-2} s^{-1})$. Proliferating shoots and plantlets were photosynthetically active. Better shoot growth and accumulation of higher biomass occurred in a$CO_2-enriched$environment than under ambient CO2conditions. CO2assimilation efficiency, however, was higher under the latter conditions than in a$CO_2-enhanced$environment, e.g.,$31 \pm 7$and$17 \pm 2 \mu mol CO_2 m^{-2} s^{1}$, respectively. The net CO2assimilation rates of in vitro grown plantlets were comparable to those of seedlings ex vitro.