Abstract
The comparative morphology and anatomy of leaves between the coastal ecotype and the normal type of Adenophora triphylla (Thunb.) A.DC. var. japonica (Regel) H.Hara (Campanulaceae) were examined to clarify the differences in morphological characters between the 2 groups. Morphological and anatomical analyses revealed that the coastal ecotype had a thicker leaf than the normal type, because of the increased size of epidermal and spongy cells. Thus, the main morphological change from the normal type into the coastal ecotype of A. triphylla var. japonica is the increase in leaf size, suggesting that the coastal ecotype may have evolved from the normal type via a heterochronic process.
Highlights
Plant diversity has fascinated humans throughout history; the diversity is presumably plant adaptation to different natural environments, primarily due to the tremendous variations in morphological traits that exist in nature
The main morphological change from the normal type into the coastal ecotype of A. triphylla var. japonica is the increase in leaf size, suggesting that the coastal ecotype may have evolved from the normal type via a heterochronic process
We found the coastal ecotype of A. triphylla var. japonica, which has thick leaves and stems (Figure 1), in some coastal areas of Kochi Prefecture in Japan (Figure 2), where it grows along with other coastal taxa such as Cirsium maritimum Makino (Asteraceae), Dianthus japonicus Thunb. (Caryophyllaceae), Setaria viridis (L.) P.Beauv. var. pachystachys (Franch. et Sav.) Makino et Nemoto (Poaceae), and some CAM plants of Crassulaceae
Summary
Plant diversity has fascinated humans throughout history; the diversity is presumably plant adaptation to different natural environments, primarily due to the tremendous variations in morphological traits that exist in nature. Plant species growing in coastal regions need to be adapted to an environment in which drought strongly affects plant growth [3]. Water availability is the main environmental factor limiting photosynthesis and growth even in plants well adapted to coastal conditions [3]. Another source of stress and an abiotic driver of natural selection in coastal plant communities is soil salinity [4,5]. Plants in coastal regions have developed various interesting morphological adaptations including succulent tissues to store water, a pubescent epidermis and a thick cuticle to reduce transpiration and water loss, belowground structures to withstand sand burial, and an annual habit [8]
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