Cadellia pentastylis (Surianaceae) is an Australian endemic threatened rainforest tree. Irregular flowering and fruiting events coupled with high rates of infertility and insect predation has meant that seed testing has not been possible for this species. Seeds were opportunistically collected from a wild population in early 2021, which allowed for the first germination tests to be conducted. In this study, the presence of physical dormancy was examined by performing an imbibition test using scarified and non-scarified seeds. We also investigated whether a 5-min heat shock treatment at temperatures ranging from 60 to 120°C improved germination success. The presence of physiological dormancy was also examined by recording germination success following a gibberellic acid or smoke-water pre-treatment. Both scarified and non-scarified seeds readily imbibed water over a 72-h period, and several seeds had germinated in both treatments after 48 h. Final germination proportion and t50 following a heat shock, gibberellic acid or smoke-water pre-treatment did not significantly differ from the controls. We conclude that C. pentastylis seeds are non-dormant. Although a palisade cell layer has been reported in the endocarp, our results suggest that this layer may not be sufficiently formed to restrict germination. We recommend that seeds are collected from populations following dispersal and propagated shortly after or stored as conservation collections in ex situ Seedbanks.

Solanum viarum, commonly known as tropical soda apple(TSA), is native to Brazil and Argentina but has become a harmful weed inmany countries with tropical climates. This study was conducted to reassessthe seed biology of TSA found in South Africa. Cold stratification (14 d),acid scarification (20% H2SO4 for 5 min), andsandpaper scarification (30 s) significantly improved percentage germinationwhen compared to the control. The highest germination (99.5%) was achievedwhen seeds were germinated in 50% Hoagland's nutrient solution (HS). Thelowest germination (66%) was recorded in the absence of phosphorus (P) underalternating light conditions. HS without nitrogen (N) completely inhibitedseed germination of TSA under constant light conditions. These findings areuseful in controlling TSA by amending the levels of N and P in soils. Seedgermination of TSA was significantly enhanced by different concentrations ofsmoke-water and butenolide solution. Smoke-water dilution of 1:500 v/v andbutenolide concentration of 10−8M showed the highest seedlingvigor indices (6,688 and 6,666, respectively) in comparison to the control(1,251) and gibberellic acid (GA3) concentrations (< 5,327).These findings suggest that germination of seeds or seedbanks of TSA mightbe successfully stimulated using smoke solutions. Subsequently, patches ofseedlings emerging after treatment can be mechanically uprooted to reducethe infestation of TSA. However, justifying this with field trials isessential.

Smoke-water (SW), karrikinolide (KAR1) and vermicompost leachate (VCL) have been reported to possess gibberellic acid-like activity. The effects of these plant growth-promoting substances (PGPSs) on biochemical changes occurring during seed germination of Phaseolus vulgaris were assessed. Seeds were incubated/germinated under dark conditions in water (control) or with different concentrations of SW, KAR1, VCL and gibberellic acid (GA3) for 7 d. The maximum seedling fresh weight (1.863 g) was recorded for the SW (1:750 v/v) treatment. The longest seedling axes (9.9 cm) and the highest number of adventitious roots (16.3) were recorded for VCL-treated seedlings (1:10 and 1:5 v/v, respectively). Analysis of two important hydrolytic enzymes, acid phosphatase and alpha-amylase, showed maximum activity [1856 nkat mg− 1 and 3.225 mg min− 1(g FW)− 1, respectively] in the seeds incubated with 10− 8M KAR1. In all the treated seedlings, proline content was significantly reduced [43.67 μg (g FW)− 1; VCL (1:20 v/v)] in comparison to the control [87 μg (g FW)− 1] but there was an increase in amino acids with some concentrations of PGPSs. The tested PGPSs significantly influenced various biochemical parameters that play a significant role in seed germination and plant growth. This study indicates that PGPSs may act via stress-relieving biochemical pathways during seed germination.