Effects of tomato seed maturity on seed quality and endogenous hormones

Seed growth and development involves the coordination of hormones. The quantity of hormones varies markedly according to the seed development stage and plant genotypes. This study evaluated the correlation of endogenous hormones with seed quality of tomatoes during maturation. Tomato fruits were harvested at 40, 50 and 60 d after pollination (DAP). For each harvesting stage, dried seed qualities were determined including the number per fruit, weight of dried seed per fruit, percentage of germination (G), abnormal seedlings and ungerminated seeds, germination index (GI), and hormone contents [indole-3-acetic acid (IAA), gibberellic acid (GA1 and GA4), derivatives of cytokinin (CKs): trans-zeatin (tZ), dihydrozeatin (DZ), isopentenyl adenine (iP) and abscisic acid (ABA)]. The results showed that the fully mature embryo or the physiological maturity of tomato seed is onset at 50 DAP. The number of mature seeds per fruit during the maturation phase has no relationship with the four hormones. The increase in weight of dried seed per fruit and germination percentage at matured stage had a similar trend with GAs (especially GA4) and IAA contents, but exhibited a different trend with ABA and total CK contents. On the other hand, the percentage of abnormal seedlings and ungerminated seeds had a similar trend with ABA and CKs but had a negative trend with the total active GAs. The highest GI at 50 DAP could have resulted from significantly high content of IAA. In the tomato line used, GA4 was more dominant than GA1 in enhancing germination. In the case of CKs, DZ and iP forms of CKs were more dominant than the tZ.