Seed dormancy and germination in Dodonaea viscosa (Sapindaceae) from south-western Saudi Arabia

Abstract

Dodonaea viscosa (Sapindaceae) is widespread in the mountainous highlands of the southwestern part of Kingdom of Saudi Arabia, where it is a medicinally important species for the people in Saudi Arabia. Seeds of this species were collected from Mount Atharb in Al-Baha region, at an altitude of 2100 m. The aims of this study were to determine if the seeds of D. viscosa have physical dormancy (i.e. a water-impermeable seed coat) and, if so, what treatments would break dormancy, and what conditions promote germination after dormancy has been broken. The dormancy-breaking treatments included: soaking of seeds in concentrated sulfuric acid (H 2 SO 4 ) for 10 min, immersion in boiling water for 10 min and exposure to 50 °C for 1 min. After seeds had been pre-treated with H 2 SO 4 , to break dormancy, they were incubated at constant temperatures from 5 to 35 °C, under 12-h photoperiods or in continuous darkness, and germination recorded. Salinity tolerance was investigated by incubating acid-scarified seeds in different concentrations of mM NaCl in the light at 25 °C. Untreated seeds had low final germination 30%. Seeds that had been acid-scarified, immersed in boiling water or exposed to 50 °C all achieved 91% subsequently when incubated at 25 °C. Thus, seeds of this species in Saudi Arabia have physical dormancy, which can be broken by all three treatments designed to increase the permeability of the testa. After pre-treatment, there was a broad optimum constant temperature for germination that ranged between 5 and 25 °C but germination was inhibited by higher temperatures (30 and 35 °C). Light had little effect on this germination response. Scarified seeds were also sensitive to salinity, with the highest germination in distilled water and complete inhibition in 400 mM NaCl. Seeds that failed to germinate in saline treatments were mostly able to germinate on transfer to distilled water, suggesting osmotic inhibition.

Pre-sowing treatments for enhancing germination of Guibortia coleosperma and Amblygonocarpus andongensis seeds from Kazuma Forest Reserve, Botswana

“…The fact that concentrated sulphuric acid enhanced the germination of A. andongensis infers that the seed coat is a barrier to the germination of the species. This result is consistent with studies conducted on other plant species elsewhere which showed that concentrated sulphuric acid increased germination percentage (Filho et al, 2019;Al-Namazi et al, 2020).…”

Effect of Pre-Germinative Treatments on Eight Priority Native Species for Reforestation in the Tropical Deciduous Forest

“…After the treatments, the seeds were soaked in running water for 24 h. The temperatures (TS) and times of immersion (CS and TS) were based on specific literature for the selected Conservation 2023, 3 282 species that report the use of temperatures between 65 • C and 100 • C [32,36,39,42,45,51,80]. For CS, sulfuric acid was used at different concentrations and immersion times for the same species [42,44,47,81]. Planting was carried out manually in Styrofoam seedbeds with alveoli of 5 cm in diameter and 20 cm deep, which were previously sterilized with a 2% solution of commercial sodium hypochlorite.…”

“…After the treatments, the seeds were soaked in running water for 24 h. The temperatures (TS) and times of immersion (CS and TS) were based on specific literature for the selected species that report the use of temperatures between 65 °C and 100 °C [32,36,39,42,45,51,80]. For CS, sulfuric acid was used at different concentrations and immersion times for the same species [42,44,47,81].…”

“…It is important to keep these properties in mind while developing restoration strategies in order to make it possible for productive forests to continually adapt to site conditions [30]. Therefore, several studies have proposed the evaluation of seed characteristics and their behavior under laboratory and field conditions [16,[31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47].…”

“…Pregermination treatments are among the most important activities in a forest nursery, and the use of the most adequate treatment for each species ensures the success of plant production [32,48,54]. Although propagation protocols have been published for TDF species of trees and shrubs, most of them were conducted in vitro under controlled conditions and the species included were not representative of the great diversity found in the TDF [32,33,36,[38][39][40][42][43][44][45]47,51,52].…”