Degree of seed desiccation sensitivity of the Amazonian palm Oenocarpus bacaba depends on the criterion for germination

Lydiane Lucia De Sousa Bastos,Geângelo Petene Calvi,Isolde Dorothea Kossmann Ferraz,Manuel De Jesus Vieira Lima Júnior

doi:10.1590/1809-4392202001951

Abstract

ABSTRACT Across the seed-seedling transition, several germination criteria are used in studies of palm-seed germination. In Oenocarpus bataua, these criteria have differential tolerance to thermal stress. In this study, we evaluated the tolerance of germination criteria to seed desiccation of the congeneric Oenocarpus bacaba. We dried seeds to different moisture contents (MC) before scoring first cataphyll, second cataphyll, enclosed eophyll and expanded eophyll. Seeds without drying had 41.7% MC. Germination success reached close to 70% after 75 and 105 days, depending on the germination criterion. Safe MC was close to initial MC and all seeds were dead with MC < 26.7%. As the primordial organs of the cataphylls and the eophyll are already detectable in the palm-seed embryo, all were affected by drying. Critical MC, defined here as 50% loss of germination capacity, increased from 35.4% (first cataphyll) to 37.1% (expanded eophyll) and confirmed that, across the seed-seedling transition, more advanced germination stages had a higher sensitivity to desiccation. During germination and development, the criteria appear in sequence over several weeks. Consequently, the desiccation damage was only detectable when the last criterion was evaluated. To avoid an underestimation of damages, we suggest that seed-stress studies in palms should take into account an adequate period for seedling development, which, for O. bacaba, was 105 days until the expansion of the eophyll.

Highlights

The global distribution of palms is mainly restricted to tropical and sub-tropical climates, and only a few species are found in warm-temperate regions (Dransfield et al 2008)
The present study aimed to evaluate the tolerance of four seedling development stages used as emergence criteria to different levels of desiccation stress in O. bacaba seeds
In a previous study on seed desiccation of O. bacaba that scored the protrusion of the germinative bud and the growth of the primary root (> 2 mm), the control (MC = 39.9%) had the highest germination percentage and all seeds were dead after drying to a moisture contents (MC) of 26.6% (José et al 2012)

Summary

Introduction

The global distribution of palms (family Arecaceae) is mainly restricted to tropical and sub-tropical climates, and only a few species are found in warm-temperate regions (Dransfield et al 2008). Of the 124 palm species studied so far, a similar percentage of desiccation-tolerant (29%) and desiccationsensitive seeds (33%) has been identified (Royal Botanic Gardens Kew 2020). Several germination criteria during initial development were used for germination assessment: the germination button (Beckman-Calvacante et al 2012), primary root development (Iossi et al 2003; Silva et al 2006; José et al 2012), first and/or second cataphyll (Bastos et al 2017) or expanded eophyll (Nazario and Ferreira 2012). Four development stages during the seed-seedling transition of Oenocarpus bataua Mart. We aimed to assess whether stages of development in palm seeds differ in tolerance to desiccation. The seeds of this species are known to be sensitive to desiccation, only the germination button and radicle growth had been assessed (José et al 2012)

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