Seeds are one of the most important organs in spermatophytes. The seed coat is believed as a major physical barrier between embryos and external environments. Many plants invest a considerable amount of biomass in the seed coat; however, the relative biomass allocated to the seed coat, that is the seed coat ratio (SCR) varies greatly across plant species.The relative importance of the factors contributing to such large interspecific variation in the SCR has not yet been quantitatively evaluated. 

In a study published in Functional Ecology, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) and Anhui University provided the first quantification of the relative explanations of six factors that have been commonly considered to be associated with the interspecific variation in SCR.They highlighted the important roles of seed desiccation response and seed dormancy in explaining interspecific variation in the SCR.  

The researchers compiled a global database of the seed coat ratio, a proxy of seed physical defence, for 1362 species. They verified the association of six factors that have been commonly considered to be associated with the interspecific variation in SCR, including seed mass, seed desiccation response (desiccation-sensitive vs. desiccation-tolerant), seed dormancy (nondormant, physical dormant or other dormant types), growth form (herbaceous vs. woody), fruit type (dry vs. fleshy) and climate (19 bioclimatic variables representing temperature and precipitation). 

Their global-scale study successfully disentangled the relative explanations of the six most frequently discussed factors associating with interspecific variation in the SCR. Seed desiccation response was shown to be the most important factor associating with the interspecific SCR variation, indicating that natural selection imposed by drought stress may be much more important than any other abiotic or biotic factors in determining the SCR.  

Furthermore, seed dormancy showed a modest contribution to interspecific variation in SCR, indicating that biotic and abiotic stresses that are related to seed dormancy may have an indirect effect on SCR variation. However, growth form, climate, fruit type and seed mass were irrelevant for explaining SCR variation. 

" Our findings shed some light on the ecological patterns underlying the physical defence mechanisms and allocation strategies of plant seeds,” said WU Lamei of XTBG. 

Contact 

WU Lamei  Ph.D 

Center for Integrative Conservation, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, Mengla, Yunnan 666303, China
E-mail: wulamei@xtbg.ac.cn
First published: 20 March 2024