Photosynthetic and ultrastructural adaptability of Anemone shikokiana leaves to heterogeneous habitats

Abstract

Anemone shikokiana (Makina) Makina is distributed in two heterogeneous habitats, including mountaintop shrubland and conifer and broad-leaf mixed forest. To better understand the mechanisms used by A. shikokiana in adapting to these different environments, the photosynthetic efficiency, chlorophyll fluorescence and ultrastructure of the leaves were investigated. The findings revealed that, under the same optical quantum flux density, the net photosynthetic rate in the leaves of mountaintop shrubland was significantly higher than that found in the mixed forest, but the stomatal conductance, intercellular CO2 concentrations and transpiration rate were lower. The effective quantum yield of photosystem II (PSII), photochemical quenching coefficient, non-photochemical quenching coefficient and electron transfer rate in the conifer and broad-leaf mixed forest were significantly lower than those values determined for plants in mountaintop shrubland. However, the maximal quantum yield of PSII exhibited no significant difference between the two habitats. Transmission electron micrographs revealed that the numbers of chloroplasts and mitochondria per mesophyll cell and starch grains per chloroplast in the mountaintop shrubs were higher than those found in the conifer and broad-leaf mixed forest samples. Moreover, they showed an increasing trend month by month in April, May and June. It indicated that elevated temperature increased their numbers. These findings illustrate that A. shikokiana efficiently uses environmentally limited resources to adapt to different living environments. The study reveals that the mechanisms that underlie the response of A. shikokiana to heterogeneous habitats involve photosynthetic and ultrastructural variations, thus providing a theoretical basis for future study.