Effects of shading on phenotypic plasticity, clonal characteristics, and reproduction index of Euphorbia thymifolia

Euphorbia thymifolia is a wild native turfgrass germplasm resource, whose shade tolerance and coping mechanisms determined its values of development and utilization. In this experiment, we treated the seedlings of E. thymifolia under four shading degrees of 0 (CK), 30%, 50%, and 70% for four months. In summer, the component properties, biomass structure, cloning efficiency indexes and sexual reproduction indexes of the genet were determined, to analyze the growth and reproduction strategy of E. thymifolia under different degrees of shading. The results showed that: 1) E. thymifolia exhibited altered quantity and quality character components by decreasing leaf number, leaf area, stolon length, branching strength, root diameter and so on (P < 0.05), to adapt to or respond to shade stress. 2) The response order of leaf characteristics to shading was number > total leaf area > length > single leaf area > width > thickness, that of stem characteristics was branch strength > plant height > stolon length > branch density > primary branch number, and that of root characteristics was indefinite root number > main root diameter > lateral root number > main root length. 3) With a decrease of genet biomass under shading (P < 0.05), E. thymifolia adjusted the component biomass allocation ratio to form a growth strategy adapted to the shading degree. 4) E. thymifolia could reduce the sexual reproductive allocation and reproductive index to cope with > 30% shading (P < 0.05), simultaneously decreasing the clonal structure biomass and cloning efficiency index to adapt to the shading habitat (P < 0.05). In summary, E. thymifolia is a light-loving plant, with a strong ability to adjust the component traits and biomass structure according to shading degrees, and thus, clonal growth and sexual reproduction could be adapted to the environment.