Photosynthetic performance and growth responses of Liriope muscari (Decne.) LH Bailey (Asparagaceae) to different levels of irradiance in three seasons

Plants in natural environments are often exposed to different irradiance in different seasons, and leaf-level acclimation to light may be affected by those changes. To investigate this, photosynthetic characteristics of lilyturf (Liriope muscari), a shade-tolerant evergreen groundcover of forest origin native to East Asia, were compared in summer, autumn and winter in plants growing in two light environments: an open field with high irradiance (HI) and under a winter-deciduous forest canopy (LI). Light saturation point, light compensation point, photon-saturated photosynthetic rate and in situ net photosynthetic rate (PN) were highest in HI, as was whole-plant biomass. Photon-saturated rates of net photosynthesis were higher in autumn and winter than in summer. Substantial declines in PN, stomatal conductance (gs) and intercellular CO2 were observed in HI plants during midday in summer, but not in LI or in autumn and winter. Chlorophyll fluorescence indicated that HI plants were photoinhibited during midday in both summer and winter and consequently performed best in autumn. In contrast, LI plants were light-limited in summer and performed better when the canopy was leafless, especially in winter. Winter and autumn photosynthesis may make critical contributions to the carbon economy of lilyturf integrated over the year, facilitating its growth and survival in a wide range of light environments.