Reproduction biology of the round-leaved sundew (Drosera rotundifolia L.) with special attention to its ex situ conservation
Abstract
The aim of our study is to provide information on the ex situ conservation of the insectivorous round-leaved sundew (Drosera rotundifolia L. 1753). This glacial relict plant with circumboreal distribution is considered threatened, thereby it is protected in Hungary. Recently, habitat loss and degradation raise serious concerns regarding the survival of the Hungarian populations. We examined the reproduction biology of the species in order to elaborate a more efficient ex situ preservation protocol. Altogether, 11,400 seeds were sown in different treatments. The seed samples were obtained from two different sources. Part of the seeds were produced by plants obtained from horticulture (Netherlands), while the other group of seeds was collected from natural habitat in the Őrség National Park, SW Hungary. We studied seed morphology quantitatively on high resolution digital photographs by using a pixel-based image analysis program. In a greenhouse experiment, we tested the influence of light, vernalization and different substrates on the success of germination. The efficiency of propagation of the plant from leaf cuttings were also examined. No difference was observed in seed morphology between the two groups with different source of origin. This suggests a high degree of homogeneity of seed traits for the species. Average seed size was 1.46 × 0.21 mm and the small (0.20 mm × 0.10 mm), ellipsoidal embryo is pale dark brown in color and it has a smooth surface with delicate stripes on it. Our results confirm that seeds require vernalization for germination. We observed the following tendency: the longer vernalization period the seeds received, the more successful germination could be observed. Maximum vernalization time used here was 5 weeks, but it would be appropriate to examine longer periods of treatment. Our experiment also confirmed that the seeds of this species need light for their germination. The living Sphagnum moss used in horticultural practice proved to be the best substrate for germinating D. rotundifolia seeds. Propagation from leaf cuttings was effective, thus maintaining the species ex situ is more efficient and faster than reproduction from seed. We consider this method as an emergency solution to reintroduce the plants to natural habitats due to the low genetic diversity.
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