Water immersion and one-year storage inuence seed germination of Copernicia alba palm tree from a neotropical wetland

54 Copernicia alba (Morong ex Morong & Britton) is a palm tree native to tropical and subtropical climates, commonly 55 named “ carandá ” , that often forms monodominant populations in the Pantanal wetland in Brazil. Currently, 56 the knowledge of the seed germination behavior of C. alba is still limited, as well as seed viability in ex- 57 situ conservation under laboratory conditions. Hence, this study investigated the effect of water treatments and a one- 58 year storage period (at 19°C under a relative humidity of 45%) on its germination. We subjected fresh and stored 59 seeds to immersion in water at room temperature (~25°C) for 24, 48, and 72 h; and hot water (~75°C) for 5 min and 60 10 min. The results showed that seeds do not have primary dormancy, with fresh seeds germinating 84% in the control. 61 Additionally, fresh seeds had a significant increase in germination percentage (reaching 100%) and faster germination 62 times after immersion in water for 48 and 72 h. On the other hand, hot water treatments decreased germination for 63 both fresh and stored seeds. One year of storage reduced the germination capacity by almost 50%. We concluded that 64 seeds of C. alba may be easily germinated under laboratory conditions for seedling production, and water immersion 65 at room temperature can improve the germination of fresh seeds. However, long-term seed storage and hot-water 66 treatments may jeopardize germination. Future studies should further investigate ex-situ conservation of seed of C. 67 alba under extended periods, considering seed desiccation and alternative storage conditions, to improve seed 68 conservation techniques. 69


Introduction
Tropical wetlands cover extensive areas of the Earth's surface and are one of the most diverse ecosystems

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Considering the current limited knowledge in seed germination and storage behavior of Copernicia alba, and 123 the fact that it colonizes the Pantanal areas, which are periodically subjected to flooding followed by dry periods, the 124 present study aimed to evaluate the effect of water treatments and storage on seed germination. We investigated: (a)

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In the storage experiment, fresh seeds were wrapped in kraft paper bags and kept them stored in a cold 154 chamber at 19°C (relative humidity 45 ± 5%) for one year. After this period, two samples of 15 seeds each were used 155 to determine the seed water content (Brasil 2009) (see seed collection and benefiting subsection). Then we subjected 156 stored seeds to immersion in water treatments (at room temperature and hot water) and used a sample of stored seeds 157 as control (untreated seeds). Seeds (treated and control) were set to germinate in a rolled paper towel as described

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Initial seed water content was ~10% for fresh-harvested seeds and decreased to 7% after the one-year period 171 of storage. Copernicia alba seed shows no dormancy type. Fresh-harvested seeds germinated 84% (Fig. 2a),  (Fig. 2b). Water treatments (48 and 72 h) reduced the mean germination time values of fresh seeds (around 20 days) compared to control (25 days, Fig. 2c), providing faster germination. In contrast, there was no change 184 in the mean germination time of stored seeds (Fig. 2d). A short period of immersion in water may improve the 185 germination of C. alba fresh seeds for seedling production. As well, water immersion treatments promoted

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In contrast, hot water treatments decreased the germination percentage of fresh seeds to 62 and 50% for 5 194 and 10 minutes of exposure, respectively (Fig. 2a, b). Such treatments also decreased the germination percentage of 195 stored seeds to 21% for 5-min and 16% for 10-min of exposure (Fig. 2b). Additionally, the 5-min hot water treatment 196 delayed the mean germination time of fresh seeds for 30 days (Fig. 2c), with no effect on this parameter after storage 197 (Fig. 2d). Likewise, hot water treatments jeopardized the germination of Euterpe oleracea seeds from the Amazon 198 rainforest (Bovi and Cardoso 1976). Thermal shock also did not promote the seed dormancy of Acrocomia aculeata 199 (macaw palm) but rather caused high seed deterioration rates (Rodrigues-Junior et al., 2016).

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In general, the one-year storage period decreased germination percentage to ≤50%, with no change in 201 germination time (Fig. 2b, d). Ex-situ conservation of seed plants is a worldwide concern (Walters et al.

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Seeds of C. alba should be considered orthodox, given the seeds water content ranges from 10 to 7% depending on 205 the storage period. Hong and Ellis (1996) define as recalcitrant seeds those sensitive to desiccation ≤12%; thus, seeds 206 of C. alba can be classified as desiccation-tolerant (orthodox), due to their relatively low initial seed water content.

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The natural habitats where this species occurs can experience prolonged events of drought in pluriannual dry years of         Germination percentage (%) and mean germination time (MGT, days) of fresh-harvested (a) and one-year stored seeds (b) of Copernicia alba, from a natural population, under water immersion (W) treatments for 24, 48, and 72 h (at room temperature), and hot water (Hot, 75°C) for 5 and 10 minutes of exposure compared to their respective controls. Asterisks indicate signi cant differences (blue refers to a signi cant increase, red to a signi cant decrease, always compared to controls). * = P <0.05; ** = P <0.01; *** = P <0.001; n.s = non-signi cant; Cont = control