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<p><i>Borassus flabellifer</i> L. (Arecaceae) produces large, recalcitrant diaspores (seeds) exhibiting a complex morphophysiological dormancy (MPD) that remains poorly characterized. Here, we aim to resolve dormancy classification of <i>B. flabellifer</i>, assess moisture thresholds affecting viability, and elucidate key morphogenetic traits supporting germination, seedling establishment and survival in dry tropical habitats. Mature fruits were collected, and fruit/seed physical and seed moisture parameters were measured. Germination was monitored from the emergence of the cotyledonary petiole (CP) through the appearance of radicle (true root) and the first true leaf under controlled laboratory and simulated natural soil burial conditions. Seed desiccation tolerance was evaluated by drying seeds to different moisture contents. Seeds had an underdeveloped embryo. CP emerged in &gt; 90% of seeds within 30 days after incubation and elongated fully by 50 days; radicle emergence followed at 60–75 days after incubation (10–15 days after full elongation of CP). Shoot development was much delayed (~ 240 days after CP and ~ 200 days after radicle emergence), indicating morphophysiological dormancy (MPD), with epicotyl showing physiological dormancy (PD). Seeds lost viability below ~ 40% moisture content, confirming desiccation sensitivity. Germination followed remote tubular pattern characterized by substantial CP elongation (15–35&#xa0;cm), transporting the embryo axis into the soil, accompanied by haustorial expansion. Deep burial and moist soil conditions were critical in protecting emerging tissues from desiccation and predation, thus promoting successful establishment. Thus, <i>B. flabellifer</i> seeds have MPD with epicotyl subclass, represented by the formula CₓbB(rs)′b′, encompassing PD broken by warm stratification (epicotyl dormancy), an underdeveloped embryo requiring post-dispersal growth, and remote tubular germination involving fully cotyledonary petiole elongation before initiation of true root and leaf emergence.</p>

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Epicotyl morphophysiological dormancy in Borassus flabellifer goes beyond synchronizing seasonal leaf emergence to safeguard epicotyls from desiccation stress through deep burial

  • 期刊论文

  • 发表日期：

    2025年12月4日

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  • Simbarashe Mudavanhu,
  • Ganesh K. Jaganathan,
  • Shyam S. Phartyal

摘要

Borassus flabellifer L. (Arecaceae) produces large, recalcitrant diaspores (seeds) exhibiting a complex morphophysiological dormancy (MPD) that remains poorly characterized. Here, we aim to resolve dormancy classification of B. flabellifer, assess moisture thresholds affecting viability, and elucidate key morphogenetic traits supporting germination, seedling establishment and survival in dry tropical habitats. Mature fruits were collected, and fruit/seed physical and seed moisture parameters were measured. Germination was monitored from the emergence of the cotyledonary petiole (CP) through the appearance of radicle (true root) and the first true leaf under controlled laboratory and simulated natural soil burial conditions. Seed desiccation tolerance was evaluated by drying seeds to different moisture contents. Seeds had an underdeveloped embryo. CP emerged in > 90% of seeds within 30 days after incubation and elongated fully by 50 days; radicle emergence followed at 60–75 days after incubation (10–15 days after full elongation of CP). Shoot development was much delayed (~ 240 days after CP and ~ 200 days after radicle emergence), indicating morphophysiological dormancy (MPD), with epicotyl showing physiological dormancy (PD). Seeds lost viability below ~ 40% moisture content, confirming desiccation sensitivity. Germination followed remote tubular pattern characterized by substantial CP elongation (15–35 cm), transporting the embryo axis into the soil, accompanied by haustorial expansion. Deep burial and moist soil conditions were critical in protecting emerging tissues from desiccation and predation, thus promoting successful establishment. Thus, B. flabellifer seeds have MPD with epicotyl subclass, represented by the formula CₓbB(rs)′b′, encompassing PD broken by warm stratification (epicotyl dormancy), an underdeveloped embryo requiring post-dispersal growth, and remote tubular germination involving fully cotyledonary petiole elongation before initiation of true root and leaf emergence.