Growth of carob, accumulation of inhibitor and seed germination

The growth in length and weight of immature fruit and seed of carob (Caratonia siliqua L.) was studied over a period of seven months. During the early periods of development, seed and fruit growth follow a parallel course; however, the seed continue to grow even after the fruit growth has ended. The embryo and endosperm grow at a faster rate than the seed coat during this later phase of growth. Extracts for growth inhibitors were also made from the developing fruit. All the extracts were significantly inhibitory in the pea bioassay at concentrations of extract from 0.5 mg FW/plant. During the last two months of growth prior to desiccation quantitative extractions of inhibitor from the seed coat, endosperm and embryo were made. At least 92% of the inhibitor in the seed is concentrated in the seed coat. The whole extract and one partially purified fraction, C, were studied for the effect of germination of ripe carob seed. They were found to delay germination, inhibit the growth of the germinating seed, and to decrease the amount of reducing sugar in the medium of the germinating seed. It is inferred that the inhibitor imposes a block to either the synthesis or the release of enzyme(s) involved in the breakdown of the reserve galactomannnan.