Starch, storage protein and triglyceride accumulation and respiration in developing embryos in Hevea brasiliensis

Starch, storage protein and triglyceride contents and respiratory rate were studied in an embryogenic strain of Hevea brasiliensis during development of somatic embryos. For comparison, a non-embryogenic strain was also investigated. The development of somatic embryos was studied on a medium containing polyethylene glycol and abscisic acid, and a medium devoid of both. Somatic embryos were almost lacking on medium devoid of polyethylene glycol and abscisic acid: only 3 % of torpedo embryos versus 40 % on medium containing these substances. Storage product accumulation in somatic embryos was observed on the medium containing polyethylene glycol and abscisic acid but not on the medium devoid of both. It took place in torpedo embryos; this could explain why it was absent on medium devoid of polyethylene glycol and abscisic acid. In torpedo embryos, storage proteins and triglycerides were accumulated at the same time, followed by starch deposition. Starch, storage proteins and triglycerides represented respectively 4.4 %, 36.1 % and 53.5 % of the total reserves accumulated. In non-embryogenic cells, starch, storage protein and triglyceride levels were similar whatever the culture conditions. The respiration rate was greater in embryogenic and non-embryogenic cells cultured on the medium containing polyethylene glycol and abscisic acid than on the medium devoid of both. This stimulation of respiration could be linked with greater osmotic pressure of the medium containing polyethylene glycol. Also, when torpedo embryos were formed, respiratory rate decreased and accumulation of storage products was observed.