Contribution of the carbon sources involved in latex regeneration in rubber trees (Hevea brasiliensis): an in situ 13CO2 labelling experiment

Rubber trees (Hevea brasiliensis) are the main source of natural rubber, extracted from latex, which exudes from the trunk after tapping. Tapped trees require large amounts of carbon (C) to regenerate the latex after its collection. Knowing the contribution of C sources involved in latex biosynthesis will help understand how rubber trees face this additional C demand. Whole crown ¹³CO₂ pulse labelling was performed on 4-year-old rubber trees in June when latex production was low and in October, when it was high. ¹³C contents were quantified in the foliage, phloem sap, wood and latex. In both labelling periods, ¹³C was recovered in latex just after labelling, indicating that part of the carbohydrates was directly allocated to latex. However, significant ¹³C amounts were still recovered in latex after 100 days and the peak was reached significantly later than in phloem sap, demonstrating the contribution of a reserve pool as a source of latex C. The contribution of new photosynthates to latex regeneration was faster and higher when latex metabolism was well established, in October than in June. An improved understanding of C dynamics and source-sink relationship in rubber tree is crucial to adapt tapping system practices and ensure sustainable latex production.