Phenotypic plasticity in wild Camellia japonica across climatic zones: responses to variations in soil moisture and light intensity

Phenotypic plasticity is recognized as the important driver of adapting to the heterogeneous habitats and environment changes. The climate variability hypothesis suggests that plant populations in high latitudes experience greater environmental fluctuations and may exhibit higher phenotypic plasticity. Wild Camellia japonica is an important but small number of species, which is mainly distributed in warm-temperature and subtropical zones of China, yet it is not clear how its different populations have adapted to environmental changes. In our study, wild C. japonica from both zones were subjected to three soil moisture levels and two light intensity levels in the common garden experiments. We focused on examining the morphological and physiological responses to determine how wild C. japonica populations adapt to heterogeneous habitats and environmental changes through phenotypic plasticity. The experimental results showed that severe drought stress reduced the activity of antioxidant enzymes and damaged the antioxidant enzyme system of subtropical wild C. japonica. In contrast, warm-temperate wild C. japonica performed better under variable soil moisture conditions and had higher phenotypic plasticity to soil moisture, which confirmed the climate variability hypothesis. Meanwhile, the warm-temperate and subtropical wild C. japonica showed similar phenotypic plasticity in response to light intensity, and both could reduce the effects of light deficit by improving its ability to capture sunlight energy. The similar phenotypic plasticity to light intensity might be due to the conservative strategy of subtropical wild C. japonica to avoid resource wastage. Our study suggests that conservation efforts for wild C. japonica should account for the response mechanisms of their different populations to environmental changes, providing differentiated conservation strategies tailored to each population.