Action of compatible osmotica and growth regulators in alleviating the effect of salinity on the germination of dimorphic seeds of Arthrocnemum indicum L.

Arthrocnemum indicum Willd., a stem succulent perennial in the family Chenopodiaceae, is widely distributed along the coastal areas of Pakistan and forms an important component of the vegetation of salt marshes in the vicinity of mangrove swamps. Seed germination of halophytes is often inhibited by hypersaline conditions at these sites, which prevents the establishment of new populations (Ungar 1991). We studied the affect of growth regulators and compatible osmotica in alleviating the innate and salinity-induced dormancy in dimorphic (brown and black) seeds of A. indicum. Germination of both types of seeds decreased with an increase in salinity. Brown seeds germinated at the highest salinity concentration (1000 mM), whereas only a few black seeds germinated at 800 mM NaCl, and no germination was recorded at 1000 mM NaCl. The osmotica, proline and betaine, did not relieve salinity-induced dormancy in either black or brown seeds. Plant growth regulators, gibberellic acid (GA) and kinetin, significantly (P < 0.05) alleviated the salinity-induced germination inhibition of both seed types but over different salinity ranges and to different degrees. Both growth regulators significantly increased (P < 0.05) the rate of germination over most salinities, but the effect of GA was more pronounced than kinetin.