Salt stress in cultured rice cells: effects of proline and abscisic acid

The presence of 1 and 10 mol m−3 proline in media containing 100 and 200 mol m−3 of NaCl, had little effect on the growth of salt‐adapted callus of rice. However, in such callus proline accumulation was stimulated by 10 mol m−3 proline in the presence of 100 mol m−3 NaCl. On the other hand, with 100 mol m−3 NaCl, both 1 and 10 mol m−3 proline significantly increased both the growth and proline content of salt‐unadapted callus. On replacing NaCl with KCl (100 and 200 mol m−3), growth of saltadapted as well as unadapted callus was inhibited, but the presence of 10 mol m−3 proline had an ameliorating effect. Abscisic acid (ABA) supressed the growth of both salt‐adapted and unadapted callus of rice in the absence of salt stress. ABA inhibited the growth of callus adapted to and grown in 100 and 200 mol m−3 of NaCl or when it was replaced by equimolar concentrations of KCl. Growth of 100 mol m−3 NaCl adapted cells was inhibited when they were transferred to a medium containing 200 mol m−3 of NaCl, but in the presence of ABA it was stimulated. ABA increased the growth of unadapted cells when subjected to different salts. Also, ABA accelerated the adaptation of cells exposed to salt but not to water deficits imposed by nonionic solutes.