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 inves tigated. The development of somatic embryos was studied on a medium contain ing polyethylene glycol and abscisic acid, and a medium devoid of both. Som atic embryos were almost lacking on medium devoid of polyethylene glycol an d abscisic acid: only 3 % of torpedo embryos versus 40 % on medium containi ng these substances. Storage product accumulation in somatic embryos was ob served on the medium containing polyethylene glycol and abscisic acid but n ot on the medium devoid of both. It took place in torpedo embryos; this cou ld explain why it was absent on medium devoid of polyethylene glycol and ab scisic acid. In torpedo embryos, storage proteins and triglycerides were ac cumulated 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, stor age protein and triglyceride levels were similar whatever the culture condi tions. The respiration rate was greater in embryogenic and non-embryogenic cells cultured on the medium containing polyethylene glycol and abscisic ac id than on the medium devoid of both. This stimulation of respiration could be linked with greater osmotic pressure of the medium containing polyethyl ene glycol. Also, when torpedo embryos were formed, respiratory rate decrea sed and accumulation of storage products was observed.