GERMINATION OF SPECIES OF LABIATAE IN RESPONSE TO GIBBERELLINS

Gibberellic acid at between 1 and 1000 mg/1 was used to treat fruits of different Labiatae species kept at an unfavourable temperature for normal germination (25°C). Germination requirements were diverse, but all germinated in response to gibberellic acid. Minimum effective concentrations varied widely from 1 mg/1 with Salvia glutinosa up to 1000 mg/1 with Lycopus europaeus and Scutetlaria galericulata. When species were tested under conditions in which a proportion of the fruits germinated naturally the results suggested that, even under marginal conditions, relatively high concentrations of gibberellic acid were required to promote germination, although hypocotyl extension in each of the species responded to much lower levels (0.1 mg/1). Treatments applied to fruits of Lycopus europaeus and two Galeopsis species showed that modifications to the physical conditions of the test, such as light and temperature, produced only small changes in response to gibberellic acid. This effect was found even when situations in which a proportion of seeds germinated without gibberellin treatment were compared with conditions extremely unfavourable for germination. Comparisons of the effects of gibberellic acid (A3) and gibberellin A4 suggested that the latter promoted germination at approximately one hundred times the dilution of the former when tested on Lycopus europaeus and Galeopsis pyrenaica. Copyright © 1969, Wiley Blackwell. All rights reserved