Abstract
High salinity, high temperature and absence of light may disturb the balance in endogenous growth regulators. This may put constraint on seed germination of halophytic grasses forcing them to adopt necessary measure like going into dormancy. Germination regulating chemicals may release dormancy imposed by such factors hence effect of Thiourea (10 mM), Nitrate (20 mM), Proline (0.1 mM), Betaine (0.1 mM), GA(3) (3 mM), Kinetin (0.05 mM) and Fusicoccin (5 mu M) was studied in alleviating the inhibitory effect of a range of NaCl and temperature on seed germination of the halophytic grass Phragmites karka. Six NaCl concentrations (0, 100, 200, 300, 400 & 500 mM) were used in 12h light: 12h dark photoperiod and in complete darkness, at different temperature regimes (10/20 degrees C, 15/25 degrees C, 20/30 degrees C and 25/35 degrees C, the lower temperature corresponding to dark and the higher to light photoperiod). Highest number of seeds germinated in non-saline control and the seed germination decreased with increase in salinity at all temperature regimes. All growth regulators significantly promoted seed germination in saline and also in non-saline conditions at all thermoperiods, except at 25-35 degrees C. Only GA(3) and fusicoccin successfully alleviated salinity enforced dormancy of seeds at this thermoperiod. Growth regulators promoted germination in darkness at all temperature regimes. Rate of germination was also significantly affected by the application of these chemicals. Salt induced dormancy of P. karka seeds was broken by the application of different growth regulators. These chemicals also alleviated the temperature (GA3 and fusicoccin) and light (Nitrate) enforced dormancy from seeds of P. karka. It is concluded that germination regulating chemicals have differential effect on the seed germination of P karka. Some of them may alleviate the dormancy while others have no effect.