ISHS Acta Horticulturae 812: III International Symposium on Acclimatization and Establishment of Micropropagated Plants
POSITIVE EFFECT OF THE CO2 RELEASED BY COMMERCIAL SUBSTRATES ON THE EX VITRO GERMINATION OF COFFEE SOMATIC EMBRYOS |
| Authors: | J.P. Ducos, A. Prévot, C. Lambot, V. Pétiard |
| Keywords: | acclimatization, coconut fibres, horticulture, micro-environment, peat, pre-germination |
| Abstract:
A pilot process was set up for the annual production of 2.5 to 3.0 M Coffea canephora (Robusta) somatic embryos. This paper focuses on the ex vitro germination step which consists to acclimatize somatic embryos by growing them in the greenhouse, from the cotyledonary (without leaves and roots) to the plantlet stage. The cotyledonary embryos, having a size between 5 to 10 mm, are bulk-collected from 10-L bioreactors, glass bottles or horizontal plastic bags (up to 20-25.000 embryos/vessel). This second type of bioreactor (“Box-in-Bag”) allows a higher light transmittance to the embryos because they are more dispersed. The embryos can be stored after their spreading out in layers on coconut fibres. These storage conditions preserve their ability to develop plantlets during at least 2 months and induce their hardening as the water content decreases by 5 to 10%. For the ex vitro germination step, the embryos are then transplanted into trays containing commercial peat or coconut fibres. Usually, the embryos are grown under a 0.5 to 1 m height plastic tunnel to maintain a high relative humidity. However, a closer confinement, obtained by placing a transparent plastic covers at 2 to 3 cm above the embryos, significantly improves the germination rate. We showed that this positive effect is related to the CO2 released by the media. The CO2 concentration ranges from 0.2 to 0.6% in the micro-environment created in the containers. On the other hand, we could check that enrichment with exogenous CO2 promotes the germination when the embryos are grown on no-emitting CO2 media as rockwool cubes. The usage of the “micro-environment” method, combined with media releasing CO2, is well adapted for the acclimatization of very small vitro-plants. Particularly, this method can be a relevant alternative to the conventional one, which consists on insufflating CO2 in the atmosphere, for large-scale coffee plantlet productions in tropical greenhouses. | |
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