Abstract
Manglietia crassipes, a critically endangered species narrowly distributed on Mount Dayao in Guangxi, China, is also a species of ornamental interest whose variability has not been explored. Key factors leading to its endangerment have also not been studied. Here, two experiments were conducted to test the effects of different plant growth regulators and different storage conditions on germination characteristics of M. crassipes seeds. Fruit morphology was measured, and germination characteristics of fresh mature seeds were tested in order to assess natural seed vigor. Seeds were soaked in distilled water (control), or gibberellic acid (GA3), 6-benzylaminopurine (6-BA) or indoleacetic acid (IAA) solutions of different concentrations, for 48 h to determine their effects on seed germination. In addition, the effects of different seed storage conditions (constant 4 °C, −7 °C, −20 °C, or 25 °C for 100 days, wet stratification at 4 °C for 100 days) on seed germination were investigated. Results showed that the abortive rate of the mature fruits was high (28.9%) and fresh natural seeds had a low germination rate (G) and germination index (GI). Seed germination was inhibited with 6-BA at all concentrations, but only at less than 100 m·L−1 IAA; otherwise, IAA slightly promoted seed germination. GA3 broke seed dormancy and significantly accelerated seed germination by improving G, GI and initial germination time (IGT), especially over 2500 mg·L−1. The viability of seeds declined no matter how they were stored. However, 4 °C wet stratification storage was preferable for seed vigor and germination power. Our results suggest that the high abortive rate of fruits, low germination of the natural seed, seed dormancy and its intolerance to storage, contributed to the endangerment of M. crassipes. GA3 can break M. crassipes seed dormancy, which can be a benefit for future ornamental breeding and further protection or conservation.
Highlights
The effect of gibberellic acid (GA3 ) on dormancy and germination of M. crassipes seeds was studied as follows: seeds were soaked in water at 35 ◦ C for 24 h before putting them in 0, 200, 500, 1000, 1500, 2000 or 2500 mg·L−1 GA3, or 0, 20, 50, 100, 200, 500 or mg·L−1 6-benzylaminopurine (6-BA) or indoleacetic acid (IAA) for 48 h at 25 ◦ C
Germination percentage (G), germination power (GP), germination index (GI), and its initial germination time (IGT) of the seeds treated with GA3, 6-BA, and IAA were calculated, and the results are shown in Table 3 and Table S1
The GP and GI were significantly different from GA3, and between GA3 A1 and A6, while no significant difference existed between the two adjacent groups, e.g., A1 and A2, A2 and A3 (Table 4). These results indicate that GA3 significantly affected seed germination compared with the control, and the effects of GA3 gradually increased with increasing concentration till 2500 mg·L−1
Summary
Fragrant flowers, dense branches and leaves, and a popular aesthetic, it is commonly used as an ornamental tree [3]. It only grows in forests of altitudes of about m on Mount Dayao, Guangxi, China. In Manglietia, studies attempting to understand seed germination and dormancy have been carried out for some species such as M. grandis [20,21,22] and M. patungensis [23,24]. A series of concentration gradient experiments using the plant growth regulators GA3 , 6-BA and IAA, as well as different seed storage conditions, were applied to understand their effects on germination and dormancy of
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