Physiological and structural adaptability of Anemone shikokiana leaves
to heterogeneous habitats
Abstract
Anemone shikokiana 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 microstructure 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
shrubs was significantly higher than that found in the mixed forest, but
the stomatal conductance, intercellular CO2 concentrations and
transpiration rates 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 the shrubland plants. However, the maximal
quantum yield of PSII exhibited no significant difference between the
two habitats. Although leaf thickness was greater and mesophyll cells
were arranged more orderly and densely the mountaintop shrub leaves, the
relative degree of stomatal opening in the mixed forest samples was
higher. 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. 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 physiological and structural variations,
thus providing a theoretical basis for future study.