Proline accumulates in Casuarina equisetifolia seedlings under salt stress
2006
Tani, Chiharu | Sasakawa, Hideo
The fresh weight of Casuarina equisetifolia seedlings decreased slightly with elevation of NaCl concentration in the culture solution. Na[superscript [+]] concentration in the shoots gradually increased with increasing NaCl concentration in the culture solution and with increasing duration of the treatment. The Na[superscript [+]] level reached 150 mmol L[superscript [-]1] in seedlings treated with 500 mmol L[superscript [-]1] NaCl for 6 weeks. The proline content of the shoots increased with increasing NaCl concentration in the culture solution and reached 13.5 [micro]mol g[superscript [-]1] fresh weight in the seedlings treated with 500 mmol L[superscript [-]1] NaCl for 6 weeks. The Na[superscript [+]] concentration and proline content in the roots also increased with NaCl treatment, but the level was considerably lower than that recorded in the shoots. A highly positive correlation between Na[superscript [+]] concentration and proline content was observed in the shoots. These results strongly suggest that C. equisetifolia plants, which are highly tolerant to salt stress, primarily synthesize proline as a major compatible solute to adjust the osmotic pressure when Na[superscript [+]] accumulates in the cells, and maintain cell homeostasis under salt-stress conditions.
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