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Dormancy, germination and desiccation sensitivity in the seeds of Podocarpus drouynianus, a species growing in a seasonally hot and dry Mediterranean environment

Shane R. Turner,Michal Just,K. Dixon,Simone Pedrini

Published 2025 in Plant Ecology & Diversity

ABSTRACT

ABSTRACT Background Podocarpus drouynianus is an ecologically unique, taxonomically distinct range-restricted gymnosperm that occurs exclusively within Mediterranean woodlands in the south-west of Western Australia. Limited information is known about this species regarding seed dormancy, germination, and seed desiccation sensitivity. Aims This study aimed to determine whether P. drouynianus seeds possess dormancy, quantify the responses of seeds to a range of incubation temperatures and examine seed desiccation sensitivity (i.e. recalcitrance) after exposure to different conditions to understand recruitment dynamics in a seasonally dry environment and ex situ seed storage. Methods Fresh diaspores (seeds enclosed within an indehiscent epimatium) were collected upon maturity for experimentation. Diaspores and extracted seeds were assessed for viability, moisture content and embryo size with a subset of diaspores placed at various incubation temperatures to investigate germination response. Additional diaspores were placed under a range of storage conditions and assessed regularly for viability, moisture content and germination. Results Upon hydration, fresh diaspore germination commenced rapidly (~5 days) at several temperatures with maximum germination (0.88 germination proportion) achieved at 15°C or 20°C. Seeds were found to have morphological dormancy as embryos grew prior to radicle emergence. Fresh diaspores and seeds had a high moisture content ( > 56% - fresh weight basis) and viability (0.96 viability proportion) which declined to 45% MC and 0.75 viability proportion following storage for 42 days at 5°C and 10% eRH. Conclusions Podocarpus drouynianus diaspores germinate readily over a broad range of temperatures but were found to lose viability due to desiccation sensitivity when placed in either a cool (5°C) dry environment (~10% eRH) for 42 days or in warm (25°C) ambient (~40% eRH) conditions for 60 to 90 days. These findings are crucial for informing potential management strategies for P. drouynianus, particularly as the climate warms and dries across the south-west Australian biodiversity hotspot.

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