Pinus yunnanensis and P. kesiya var. langbianensis are the main components of forest vegetation of the central and south Yunnan, respectively. The response of the seed germination of the two pine species to the environments remains unclear. Therefore, the speculation that they may be differentiated from a common ancestor due to differences in precipitation in their respective habitats lacks evidence of the ecological adaptation of the two species.
In a study published in Forest Ecology and Management, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) and their collaborators investigated the seed germination percentages of P. yunnanensis and P. kesiya var. langbianensis under different temperature, water potential and storage conditions.
Seed germination is influenced by environmental conditions and is considered to be the most important and vulnerable stage in plant life cycle. The researchers asked what possible causes are for the differentiation of the two pine species in Yunnan.
They found that the temperature requirements for P. yunnanensis and P. kesiya var. langbianensis were similar, but the moisture requirements for the two species were significantly different. The temperature range of 15℃ to 30℃ was appropriate for seed germination and normal seedling emergence of the two pines.
Moreover, precipitation was found to be a main cause for the differentiation of the two pine species. The seed germination of P. kesiya required high moisture level, making it distributed only in southern Yunnan where is more humid than central Yunnan. However, P. yunnanensis can adapt well to drought climate and stay in central Yunnan. Thus, P. yunnanensis can outperform P. kesiya var. langbianensis at lower moisture levels.
“Therefore, the difference in the response of seed germination and storage of the two species to moisture levels may be an important factor causing the difference in their geographical distribution patterns,” said LAN Qinying of XTBG.
Germplasm Bank, CAS Key Laboratory of Tropical Plant Resources and Sustainable Use, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla 666303, China