nfYSHHX)GIA n^ANTARUM 71: 184-190. Copenhagffl 1987 The role of endc^enous gibbereUin in seed and fruit development of tomato: Studies with a g^bberellin-defident mutant P.. C. Groot, Johan Bniinsma and Cees M. Karssen Groot, S. P. C , Bruinsma, J. and Karssen, C. M. 1987. The role of endogenous gibberellin in seed and fruit development of tomato: Studies with a gibberellin- deficient mutant. - Physiol. Plant. 71: 184-190. The role of endogenous gibbereUin (GA) in seed and fmit development was studied with the use of the GA-deficient ga-1 mutant of tomato {Lycopersicon esculentum Mill. cv. Moneymaker). Flowers of the ga-1 mutant were abnormal and sterile, but parthenocarpic fmit development was observed occasionally on the dwarf plants. A single application of GA|.^7 restored the fertility of the mutant flowers and resulted in seed set. Development of GA-produeing and GA-deficient seeds in GA-deficient fmits was compared by pollination oi ga-1iga-1 flowers with wild-type or ga-1 pollen, respectively. In ga-llga-I seed dehydration started about 1 week earlier than in Ga-Ilga-1 seeds. Ultimate fresh and dry weights of mature Ga-llga-I seeds were Mghet than those of ga-Ilga-1 seeds and Snowed negative correlations witb the total number of seeds per fruit. Total content and composition of seed proteins were not influenced by the GA-deficiency. Germination of the mature seeds depended on embryonal GA synthesis and was not influenced by matemal GA production. Final fresh weight of the ga-llga-I fmits was positively correlated with the number of seeds per fruit. In these fruits, the minimum number of seeds for growth above the parthenocarpic level was about 10 or 35 in the presence of Ga-llga-I or ga-Ilga-1 seeds, respectively. Fmits containing GA-producing seeds reached a higher fresh weight than those containing GA-deficient seeds, and their ripening was delayed by one week. It is concluded that gibberellin is indispensable for the development of fertile flowers and for seed germination, but only promoting in later stages of fruit and seed development. Key words - Fruit weight, germination, gibbereBin, Lycopersicon esculentum, pro- teins, seed weight, sink activity, tomato. 5. P. C. Groot, present address, Inst. for Horticultural Plant Breeding, P. O. Box 16, 6700 AA Wageningen, The Netherlands; J. Bruinsma and C. M. Karssen (correspond- ing author), Dept of Plant Physiology, Agricultural Univ., Arboretumlaan 4, 6703 BD Wageningen, The Netherlands. tmdurtian endogenous GAs during seed development: (1) GAs are required for growth and development of the seed. Immature seeds are rich sources of gibberellins (GAs) (2) fruit growth and development are controlled by GAs and have been used in many studies concerning quanti- derived from seeds, (3) GAs interact with other plant fication and characterization of endogenous GXS (see hormones to regulate seed growth and development and Khan 1982, MacMiJlan 1984, Pharis and King 1985 for (4) GAs or GA-conjugates produced during develop- recent reviews). In fact, a great deal of our knowledge ment serve as storage forms to be utilized during germi- about GA-biosynthesis and metabolism is derived from nation and growth (Karssen 1982, Khan 1982). These studies with immattire seeds (e.g., Sponsel 1985) or suggestions are mainly based on correlations between cell-free systems derived from the seeds (e.g., Graebe changes in GA-like activity, mostly determined by bio- et al. 1980). assay, and certain phases of seed development. Care Various suggestions have been made about the role of must be taken, however, since not atl GAs that are Received 26 January, 1987; revised 30 April, 1987 184 Physiol. Plant. 71, 1987