Abstract: The influences of light spatiotemporal heterogeneity on plants have long been recognized. However, previous researches have mostly focused on responses of plants to spatially heterogeneous light conditions, little is known about how plants respond to temporally heterogeneous light conditions. Taking 1-year-old seedlings of Kmeria septentrionalis from karst habitats, Lithocarpus glaber from non-karst habitats and Celtis sinensis that occur in both habitats as objects, we compared the variations of morphological, biomass and physiological characteristics of the three species under the treatments of temporally heterogeneous light (alternating full light and heavy shading) and temporally homogeneous light (constant moderate shading and full light), to explore their responsive ability and strategies in coping with light environmental changes. Compared to moderate shading, temporal heterogeneity in light conditions increased basal diameter and decreased total biomass. Compared to the treatments of full light and moderate shading, light temporal heterogeneity treatments increased the content of osmotic substances and malondialdehyde and antioxidant enzyme activity. At the early stage, light temporal heterogeneity treatments led to an increase in the osmotic pressure of plant cells and the degree of membrane lipid peroxidation, which inhibited plant growth, but ultimately increased the daily accumulation rate of total biomass under shading. The contents of osmotic regulators and antioxidant enzyme activities of plants were reduced. The malondialdehyde content of K. septentrionalis (from karst habitat) was most stable in temporally heterogeneous light conditions, while the daily accumulation rate of total biomass was the highest at the end of treatment. In summary, the acclimation convergence of the three species in response to the same light conditions is closely related to their early experience of light availability. K. septentrionalis has evolved the corresponding responsive mechanisms in its long-term adaptation to karst habitats, it may therefore have stronger adaptability to temporally heterogeneous environments than the other two species. Such ability may be the most limited for L. glaber (from non-karst habitats).

Key words: temporally heterogeneous light condition, physiological trait, biomass accumulation, karst species