Effects of hydropriming treatments on the invigoration of aged Dodonaea viscosa seeds and water-holding polymer on the improvement of seedling growth in a lava field

Abstract

Restoration requires techniques similar to those used in agriculture to improve germination and seedling vigor. We treated 6-year-old (collected in 2003, S-2003) and 1-month-old (S-2009) seeds of Dodonaea viscosa with hydropriming (HP). Seeds were made permeable with hot water prior to hydration for 24 or 48 hours (HP-24 and HP-48, respectively) followed by dehydration. The resulting seedlings exposed to both HP treatments were sown in a lava field in soil mixed with hydrogel (HG) under the shade projected by five vegetation patches. The effects of these treatments on germination, seedling field survival, and growth were assessed. HP-24 in S-2009 and HP-48 in S-2003 increased the germination percentage from 22.5 and 31.7% in control seeds (permeable seeds) to 63.3 and 98.3%, respectively. The seedlings-2009 (from S-2009) with HG maintained high survival in all vegetation patches. Seedlings-2003, however, had low survival. The lack of HG was negatively related to the photon flux in each patch. Survival of seedlings-2009 increased with HG of up to 398.41 μmol m-2 s-1; after which survival decreased. During the rainy season, HP enhanced seedling growth, except the basal diameters and number of leaves in the seedlings-2003 with HP-24. During the dry season, the effects of HG and HP were similar for all the seedlings. In the following rainy season, the priming effect was lost while HG continued to promote seedling growth. The combined use of HP and HG and the shade projected by the patches resulted in a successful vegetation recovery strategy.