Seed imbibition and germination of Plathymenia reticulata Benth. (Fabaceae) affected by mercury: possible role of aquaporins

Abstract

Studies that evaluate the physiological and biochemical mechanisms of germination within forest species are needed in order to improve our understanding of such processes. Mercury and dithiothreitol are indicated as important tools in studies that assess the activity of aquaporins during imbibition and germination of seeds. To investigate the alterations caused by mercury in Plathymenia reticulata seeds, different doses of mercury were used in the presence and absence of dithiothreitol. Mercury had a dose-dependent effect on the seeds; in the most dilute solutions mercury partially inhibited the imbibition process, whereas in the most concentrated solutions it caused the death of the embryos. A delay in the hydration of the seeds may have caused decreased germination as a result of the reduced functionality of the aquaporins that were oxidized by mercury. In the presence of the reducing agent dithiothreitol, the activity of these proteins was restored and the germination process was re-established. These findings indicate the importance of aquaporins in the imbibition and germination stages of P. reticulata seeds, and they provide a better understanding of these important developmental events in plants.

MERCURY AFFECTS AQUAPORINS ACTIVITY AND GERMINATION OF THE EMBRYONIC AXIS OF Schizolobium parahyba (VELL.) BLAKE (FABACEAE)

“…Such results indicate that water transport through the aquaporins during phase I of imbibition was seriously affected by the presence of Hg. Similar results were found in Plathymenia reticulata seeds (Cardoso, et al, 2015) and embryonic axes of Aesculus hippocastanum (Obroucheva, et al, 2012) and Vicia faba (Novikova, et al, 2014), where hydration kinetics were inhibited by HgCl 2 in the initial hours of imbibition.…”

“…The use of DTT to unblock aquaporins inhibited by HgCl 2 during the germination process has already been shown in Aesculus hippocastanum and Vicia faba from results obtained after 15 hours of exposure to DTT (Obroucheva, et al, 2012;Novikova, et al, 2014). When DTT was used simultaneously with HgCl 2 (both 1 mM) in Plathymenia reticulata seeds, it was found that there was no inhibition of aquaporins activity during the germination process (Cardoso, et al, 2015).…”

“…However, the solution brought about reversible delays in the initial growth of the embryonic axes after root protrusion. Likewise, in seeds of Vigna radiata (Jagatheeswari and Ranganathan, 2012), Platanus occidentalis, Pinus echinata and Pinus taeda (Jean-Philippe, et al, 2012), Linum usitatissimum (Jain, 2013), and Plathymenia reticulata (Cardoso, et al, 2015), root protrusion was also negatively affected upon exposing seeds to mercury compounds during the germination process.…”

Regulation of Seed Germination and the Role of Aquaporins under Abiotic Stress

“…Aquaporins are concentrated in zones of cell division and enlargement, play a major role in governing the movement of water between neighboring cells during seed germination Jain et al 2008). Recent studies have implicated the importance of aquaporins in seed imbibition and subsequent germination (Schuurmans et al 2003; Liu et al 2007; Liu et al 2013;Cardoso et al 2015). The function of seed aquaporins may be related to the water imbibition and activation of the metabolic system in the seed, which results in higher germination (Liu et al 2007 (Beaudette et al 2007), whereas in Populus deltoides roots subjected to copper stress genes encoding plasmalemma (PIP) and tonoplast (TIP) AQPs were downregulated under Cu application (Guerra et al 2009).…”

Ação do mercúrio na germinação de sementes de Melanoxylon brauna Schott. (Fabaceae-Caesalpinoidae)

“…Os elementos traço afetam a germinação das sementes pela inibição da absorção da água, sendo altamente eficazes em inibir as atividades das aquaporinas nas sementes e nos eixos embrionários (CARDOSO et al, 2015;IOSOB et al, 2019;YÁÑEZ-ESPINOSA et al, 2020). Aquaporinas são proteínas das membranas que facilitam a passagem de água e pequenos solutos nas células (LOPEZ et al, 2012).…”