ABA-deficiency results in reduced plant and fruit size in tomato

Abscisic acid (ABA) deficient mutants, such as notabilis and flacca, have helped elucidating the role of ABA during plant development and stress responses in tomato (Solanum lycopersicum L.). However, these mutants have only moderately decreased ABA levels. Here we report on plant and fruit development in the more strongly ABA-deficient notabilis/flacca (not/flc) double mutant. We observed that plant growth, leaf-surface area, drought-induced wilting and ABA-related gene expression in the different genotypes were strongly correlated with the ABA levels and thus most strongly affected in the not/flc double mutants. These mutants also had reduced fruit size that was caused by an overall smaller cell size. Lower ABA levels in fruits did not correlate with changes in auxin levels, but were accompanied by higher ethylene evolution rates. This suggests that in a wild-type background ABA stimulates cell enlargement during tomato fruit growth via a negative effect on ethylene synthesis.

[Phenylalanine-free amino acid mixture: metabolic effects in relation to a single dose]

In the dietetic treatment of phenylketonuric patients phenylalanine free amino acid mixtures are given to meet the protein requirement of the patient. In four healthy probands we tested the metabolic effects of four different PKU-preparations given in variable amounts ingested with carbohydrate and fat containing meals. We determined glucose, insulin, amino acids, and urea in blood. Following the amino acid load we saw an increased insulin output with a hypoglycemic reaction or, with smaller amounts a lack of the normal postprandial blood glucose increase. Hyperaminoacidemias depended on the amount of amino acids ingested. The increase of blood urea found suggests that part of the amino acids were degraded. To compare the results we studied a PKU-patient. He showed corresponding but milder effects.