Plant growth regulators and flowering of Brunonia and Calandrinia sp.

Brunonia australis R. Br (Goodeniaceae) and Calandrinia (Portulacaceae), native to Australia, are potential new flowering potted plants. This research investigated the role of daylength and growth regulators, Gibberellic acid (GA3) and paclobutrazol (Pac), to control vegetative growth, peduncle elongation and flowering of Brunonia and Calandrinia. Plants were grown under long days (16 h), short days (11 h) and 8 weeks under short day then transferred to long day (SDLDs). Plants in each daylength were treated with GA3, Pac, and GA3+ Pac. GA3 was applied as 10 μL drop of 500 mg L−1 concentration to the newest mature leaf. A single application of Pac was applied as a soil drench at 0.25 mg a.i. dose per plant. Both Brunonia and Calandrinia flowered earlier in long days but still flowered in short days, so both can be classified as facultative LD plants. Brunonia under SDLDs were more vigorous and attractive than plants under LDs while still being more compact than plants under SDs. In Brunonia, GA3 promoted earlier flowering and increased the number of inflorescences under SDs. Pac at 0.25 mg a.i. per plant applied alone or in combination with GA3 had extended flower development in Brunonia, and resulted in a reduced number of inflorescences per plant compared to the control plants. Vegetative growth of Calandrinia was similar under LDs, SDs and SDLDs, whereas GA3 application increased plant size. Pac-treated Calandrinia looked compact and attractive, and Pac application did not affect time to flower and flower number.

Research highlights▶ The effect of photoperiod and plant growth regulators on flowering was evaluated. ▶ Both Brunonia and Calandrinia were facultative LD plants. ▶ Brunonia plants under SDLD were vigorous and attractive. ▶ For Brunonia GA3 promoted earlier flowering and more inflorescences under SD. ▶ For Calandrinia Pac did not delay flowering and gave high quality plants.