Control of macaw palm seed germination by the gibberellin/abscisic acid balance

Abstract

The hormonal mechanisms involved in palm seed germination are not fully understood. To better understand how germination is regulated in Arecaceae, we used macaw palm (Acrocomia aculeata (Jacq.) Lodd. Ex Mart.) seed as a model. Endogenous hormone concentrations, tocopherol and tocotrienol and lipid peroxidation during germination were studied separately in the embryo and endosperm. Evaluations were performed in dry (D), imbibed (I), germinated (G) and non-germinated (NG) seeds treated (+GA3 ) or not treated (control) with gibberellins (GA). With GA3 treatment, seeds germinated faster and to a higher percentage than control seeds. The +GA3 treatment increased total bioactive GA in the embryo during germination relative to the control. Abscisic acid (ABA) concentrations decreased gradually from D to G in both tissues. Embryos of G seeds had a lower ABA content than NG seeds in both treatments. The GA/ABA ratio in the embryo was significantly higher in G than NG seeds. The +GA3 treatment did not significantly affect the GA/ABA ratio in either treatment. Cytokinin content increased from dry to germinated seeds. Jasmonic acid (JA) increased and 1-aminocyclopropane-1-carboylic acid (ACC) decreased after imbibition. In addition, α-tocopherol and α-tocotrienol decreased, while lipid peroxidation increased in the embryo during germination. We conclude that germination in macaw palm seed involves reductions in ABA content and, consequently, increased GA/ABA in the embryo. Furthermore, the imbibition process generates oxidative stress (as observed by changes in vitamin E and MDA).

Enzyme activity and reserve mobilization during Macaw palm ( Acrocomia aculeata ) seed germination

“…Macaw palms only multiply through seeds (Ellis et al 1985), but their dormancy (Ribeiro et al 2011;Oliveira et al 2013b) will hinder the establishment of future commercial plantations. Thus, a better understanding of seed physiology and initial seedling development will be important to assure successful germination rates, and while the hormonal dynamics involved in overcoming dormancy and allowing the early germination of macaw palm seeds have recently been determined (Bicalho et al 2015;Ribeiro et al 2015), the physiology of reserve mobilization during germination and post-germination events is still poorly understood.…”

Do the structures of macaw palm fruit protect seeds in a fire-prone environment?

“…For instance, our results on seed density and fresh weight confirmed that structures of the macaw palm fruit protected the seeds exposed to the fire against the effects of high temperature. Furthermore, the lignified fruit structures in macaw palm do not limit seed imbibition or promote physical dormancy (Ribeiro et al 2011;Bicalho et al 2015). Besides certain fruit traits might be advantageous in fire-prone environments, there was no evidence that fire is a selective agent for fruit traits in the macaw palm, as detected for other plant species (Bradshaw et al 2011).…”

“…This endocarp might act as a protective structure when the palm is exposed to high temperatures promoted by fire. This species also has a low germination rate that is due to physiological traits, rather than physical dormancy (Ribeiro et al 2011;Bicalho et al 2015). A. aculeata is widely distributed throughout tropical America (Motta et al 2002;Pires et al 2013).…”

Effects of hormone balance on Korean Hackberry seed germination

“…Widely used to increase germination in certain species, GA 3 treatment has been shown to significantly promote germination in macaw palm seed (Ribeiro et al, 2011), with +GA 3 treatment, seeds reaching maximum germination in four weeks, compared to control seeds at 18 weeks (Bicalho et al, 2015). However, there is no information on the effects of adding exogenous hormones on Korean Hackberry seeds germination.…”

“…ABA can inhibit seed germination by affecting the cell cycle and synthesis of cell wall hydrolases (Miransari and Smithc, 2013). The germination rate of switchgrass seeds has been found to be reduced in solutions containing ABA (Duclos et al, 2014), and the embryos of germinated seeds of macaw palm have been found to have lower ABA concentration than in non-germinated seeds (Bicalho et al, 2015). In our research, major differences were found in the ABA concentration in all phases, in line with published research, with a lower ABA concentration detected in G seeds and a decrease of ABA during imbibition (AliRachedi et al, 2004).…”