Morphological, Growth and Photosynthetic Traits of Two Liana Species in Response to Different Light and Soil Nutrients

The present study explored the morphological, growth and photosynthetic traits of seedlings of two liana species with different climbing mechanisms — Bauhinia tenuiflora, a tendril-climbing species; and Byttneria aspera, a stem-climbing species —grown at three irradiances (4%, 35% and 100% sunlight) and low and high soil nutrient levels. Irradiance significantly affected most of the 15 phenotypic traits of the two species; however, soil nutrient affected only a few phenotypic traits. Seedlings grown under low light showed higher and more biomass investment into aboveground growth. Specific leaf area (SLA), stem mass ratio (SMR) and mean leaf area ratio (LARm) of the seedlings decreased with irradiance, under which they had higher root mass ratio (RMR) in order to improve the ability of absorption. Meanwhile, the ability for light capturing was improved by increased branch numbers. Relative growth rate (RGR), maximum photosynthetic rate (Pmax) and net assimilation rate (NAR) increased with high irradiance. When the two species were grown under the same conditions, B. tenuiflora often showed significantly higher RGR than B. aspera. Pmax was positively correlated with SLA for B. tenuiflora, and NAR but not SLA, LARm or Pmax was positively correlated with RGR for B. tenuiflora. In B. aspera, NAR was positively correlated with RGR, whereas SLA was negatively correlated with RGR. B. tenuiflora showed higher physio- and morphological plasticity in response to light and soil nutrient gradient than B. aspera. In conclusion, light is a critical factor in the distribution of lianas. With the specialized climbing tissues, B. tenuiflora might have wider distribution than B. aspera because of its higher phenotypic plasticity.