Characteristics of Iris ensata var. spontanea growing along the Tanesashi Coast, Japan: focusing on salt tolerance

Japanese wild iris (Iris ensata var. spontanea Nakai), or “Nohanashobu,” grows naturally in the wetlands of Japan.
The traditional Japanese horticultural plant “Hanashobu” has been bred using Nohanashobu since the Edo era.
Nohanashobu grows wild on the Tanesashi coast of Aomori Prefecture.
Many such coastal plants were swept away or damaged by the tsunami on March 11, 2011, induced by the Great East Japan Earthquake.
However, Nohanashobu survived and flowered as usual.
To determine the reasons for this, we measured soil and plant salt concentrations in an on-site experiment, observed the plant anatomy, and conducted histochemical analysis via greenhouse experiments.
The electrical conductivity (EC) of the tsunami-affected soil was higher than that of the unaffected soil 4 months after the tsunami.
However, 7 months later, the levels returned to normal.
Nohanashobu might have survived because the severe high-salinity conditions did not persist.
Among the leaf and root Na⁺ and Cl^– concentrations, only the Na⁺ concentration was much lower in the leaves than in the roots.
Thus, the translocation of Na⁺ from the roots to leaves was restricted.
Morphological observations showed that the Tanesashi coast seedlings had drooped and broader leaves than those of inland seedlings.
Anatomical examination revealed that the mesophyll of the leaves of the Tanesashi population consisted of numerous large cells with chloroplasts.
The vacuoles in these cells were also large, and Na⁺ preferentially accumulated in these vacuoles.
Histochemical analysis indicated that ATPase activity was high in the leaves of the Tanesashi population.
These results indicate that Nohanashobu on the Tanesashi coast had two salt-tolerance mechanisms for survival following the tsunami: restriction of Na⁺ transportation to the leaves and active isolation of toxic Na⁺ to the vacuoles.
These findings may be useful for creating a new Hanashobu cultivar with abiotic stress tolerance under high fertility conditions.

IV Asian Horticultural Congress – AHC2023

M. Nakagomi, T. Kobayashi, Y. Sadanobu, T. Tabuchi, K. Matsumoto

anatomy, histochemistry, morphology, salinity, Nohanashobu, tsunami, wetland

https://doi.org/10.17660/ActaHortic.2024.1404.156