Strongly reduced levels of endogenous abscisic acid in developing seeds of tomato mutant sitiens do not influence in vivo accumulation of dry matter and storage proteins

The role of endogenous abscisic acid (ABA) in seed development was studied with the use of the ABA‐deficient sit w ( sitiens ) mutant of tomato ( Lycopersicon esculentum Mill. cv. Moneymaker). The sit w mutation causes a strong reduction of the endogenous ABA level in the developing seed. Reciprocal crosses of wild‐type and the sit w mutant show a dual origin of ABA. The genotype of the mother plant regulates the ABA content present in the testa, which shows a peak half‐way through seed development. The genotype of the embryo and endosperm is responsible for a second ABA fraction, present in these tissues. This second fraction reaches its peak during the second half of seed development. The strong reduction of endogenous ABA level in the developing sit w / sit w seed does not change the final fresh and dry weights of the seed nor the accumulation and composition of storage proteins.