Salt tolerance of wild Oryza species, Oryza latifolia Desv., on the basis of osmotic adjustment ability of leaf blade
2004
Nakamura, I. (Ryukyu Univ., Nishihara, Okinawa (Japan). Coll. of Agriculture) | Agarie, S. | Murayama, S. | Tobita, S. | Yanagihara, S. | Kawamitsu, Y. | Motomura, K.
To elucidate the mechanisms of salt tolerance in wild rice Oryza latifolia Desv., we have tested the ability of osmotic adjustment by comparing its content of cation (K sup(+) and Ca sup(2+)) and compatible solute (proline and sucrose) in the leaves with those of salt-sensitive wild rice Oryza rufipogon, check varieties of cultivated rice (O. sativa L.), SR26B (salt-tolerance) and IR28 (salt-susceptible). When the plants were water-cultured with 6dSm sup(-1) (50mM) and 12dSm sup(-1) (113mM) NaCl for 30 days, the content of K sup(+) Ca sup(2+) were highest in the leaves of O. latifolia among the species, suggesting that this species has higher capacity of the physiological functions regulated by K sup(+) and Ca sup (2+), such as osmotic adjustment in vacuole, stomatal regulation and maintaining plasmamembrane structure. However, there was no correlation between the degree of salt tolerance estimated by dry matter production and the ratio of cation contents such as K sup(+)/Na sup(+) or Ca sup(2+)/Na sup(+) in the leaves. These indices of salt tolerance were the lowest in O. latifolia due to large amounts of Na sup(+) in the leaves of this species. Proline contents in the salt stress-leaves were higher in the salt tolerant cultivar SR26B and O. latifolia. There was the negative significant correlation between free proline content and osmotic potential in the salt tolerant species, indicating that proline participates in osmotic adjustment in the salt tolerant species. The correlation of turgor pressure and water potential showed that O. latifolia maintained turgor pressure under the salt-stress condition.
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