Abstract
Sorbus alnifolia (Siebold & Zucc.) K.Koch (Rosaceae) is an economically important tree in the temperate forests of Eastern China. In recent decades, ever-increasing use and modification of forestlands have resulted in major degeneration of the natural habitat of S. alnifolia. Moreover, S. alnifolia seeds germinate in a complicated way, leading to a high cost of propagation. The current study aimed to determine the requirements for breaking seed dormancy and for germination as well as to characterize the type of seed dormancy present in this species. Moreover, the roles of temperature, cold/warm stratification, and gibberellic acid (GA3) in breaking dormancy were tested combined with a study of the soil seed bank. The results showed that intact seeds of S. alnifolia were dormant, requiring 150 days of cold stratification to achieve the maximum germination percentage at 5/15 °C. Exposure of the seeds to ranges of temperatures at 15/25 °C and 20/30 °C resulted in secondary dormancy. Scarifying seed coat and partial removal of the cotyledon promoted germination. Compared with long-term cold stratification, one month of warm stratification plus cold stratification was superior in breaking dormancy. Application of GA3 did not break the dormancy during two months of incubation. Seeds of S. alnifolia formed a transient seed bank. The viability of freshly matured S. alnifolia seeds was 87.65% ± 11.67%, but this declined to 38.25% after 6-months of storage at room temperature. Seeds of S. alnifolia have a deep physiological dormancy; cold stratification will be useful in propagating this species. The long chilling requirements of S. alnifolia seeds would avoid seedling death in winter.
Highlights
Seeds of temperate forest plants may possess various morphological and physiological characteristics that partially represent the plant’s response to selective pressure within the current environment or previous environments during plant evolution [1,2]
This study mainly aimed to examine the conditions needed to break dormancy as well as those needed for seed germination, and to classify the type and depth of seed dormancy in S. alnifolia
Fresh seeds of S. alnifolia did not germinate in their natural habitat after sowing and none germinated at 5/15 ◦ C, 10/20 ◦ C, 15/25 ◦ C, and 20/30 ◦ C during 2 months of laboratory experiments, Fresh seeds of S. alnifolia did not germinate in their natural habitat after sowing and none indicating that freshly dispersed seeds of S. alnifolia are dormant
Summary
Seeds of temperate forest plants may possess various morphological and physiological characteristics that partially represent the plant’s response to selective pressure within the current environment or previous environments during plant evolution [1,2]. Seed dormancy contributes to screening the best time and place for seed germination; seed germination data are critical for gaining an understanding of community processes, such as the establishment and succession of plants, as well as natural regeneration [4,5,6]. On this account, seed dormancy can serve as a fundamental tool to manage the forest population [7]. Baskin and Baskin [4] have put forward five dormancy classes as part of a detailed system used to classify seed dormancy as follows: Physiological dormancy (PD), morphological dormancy (MD), physical dormancy (PY), morphophysiological dormancy (MPD), and combinational dormancy (CD)
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