Abstract
Research highlights: This study is focused on the germination of Dracaena cinnabari seeds in order to discover the possibility of natural and artificial regeneration of this species. Background and Objectives: This study aimed to determine the optimal temperature for D. cinnabari seed germination, e.g., the temperature at which the germination percentage and germination rate (vitality) are the highest. The objectives of this study are to: (1) determine the optimal temperature for the germination of D. cinnabari seeds, (2) compare the suitability of different seed collection methods, and (3) compare the germination parameters of seeds that were collected from different localities. The results of this study will contribute to obtaining the highest number of seedlings from limited seed material for reforestation of the most endangered localities of D. cinnabari species. Materials and methods: Four seed sections were employed. These sections were directly collected from either the fruits of a cut panicle or the ground and were obtained from different localities that differ in altitude. The seeds were tested in a greenhouse while using Petri dishes at three different temperatures—22, 26, and 30 °C—with four replicates of 25 seeds of each section. ANOVA and the t-test were employed for data analysis. Results: The highest germination percentages (GPs) were achieved at 26 °C and 30 °C, which were 84.6% and 82.5%, respectively. The ANOVA and t-test results showed that the germination index (GI) of the species was relatively higher at a temperature of 30 °C relative to that at other temperatures in the study. Although seeds that were collected from the tree achieved a higher GP, the t-test result showed no significant differences in the GI of D. cinnabari seeds that were collected from the ground and from the tree (p > 0.05). Overall, the findings of this study show that temperature has substantial influence on the germination of seeds of D. cinnabari. Therefore, we recommend a temperature of 30 °C to facilitate the germination of D. cinnabari, as it achieved the highest GI at this temperature relative to that at the other temperatures (22 °C, 26 °C) applied in this study.
Highlights
The Monocotyledonous Dracaena species, especially the members of the dragon tree group [1], are rare species with a limited and often scattered distribution, very limited natural regeneration, and usually very small populations
This study has focused on determining the optimal temperature for D. cinnabari seed germination, i.e., a temperature at which the germination rate, germination percentage, and germination index are the highest
The natural regeneration of Dracaena cinnabari is limited by overgrazing and climate change; will be influenced by the quantity and quality of seeds and conditions for seed germination and seedlings artificial regeneration can help to keep this species in their habitats [13]
Summary
The Monocotyledonous Dracaena species, especially the members of the dragon tree group [1], are rare species with a limited and often scattered distribution, very limited natural regeneration, and usually very small populations. Among the different Dracaena species, Dracaena cinnabari Balf.f., which is endemic to Socotra Island, has a large population with an unbalanced age structure [2]. Eighty-thousand individuals are distributed along the eastern part of the island [3,4]; most of them have over mature individuals [5], according to previous studies. The trees on the whole island do not have a problem of flowering or producing seeds when compared with, e.g., D. serrulata Baker, which flowers, according to observations, mainly after exceptional rain events [8]. Artificial regeneration would be an important practice for supporting natural regeneration, which is lacking due to overgrazing and possibly climate change [9,10,11,12,13]
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