Amino acids and soluble protein profile of radish seedlings under salt stress as affected by Ga₃ priming

Radish (Raphanus sativus L.) seeds soaked for 24 h in 10⁻⁵ M of GA₃ were germinated under 3 concentrations of NaCl (50, 100 and 200mM) and seedlings use harvested after 4, 7 and 9 d. Total soluble proteins decreased significantly with the increase of NaCl during germination except at 50mM, and the values were always higher with GA₃ priming. Proline decreased with NaCl with and without GA₃ priming. Arginine decreased with 50mM NaCl in the unprimed seedlings and increased in 50 and 200mM NaCl in the primed ones. Glutamic acid and histidine increased in 200mM salt stressed seedlings and histidine in 50 and 200mM in the primed ones. Glycine was absent in both controls and began to appear with 50 and 200mM in the primed and only in 200mM NaCl in the unprimed seedlings. Salinity increased the total essential amino acids and the increase was higher with GA₃ while the non-essential amino acids decreased slightly with 50mM NaCl and the decrease was greater with GA₃. The total amino acids accumulated with 200mM NaCl in the unprimed seedlings and the opposite was the case with the primed ones due to the sharp decrease in the non-essential amino acids. GOT activity decreased with the increase of NaCl concentration but began to increase again at 200mM NaCl in the primed and unprimed seedlings; its values were however, always, lower in the primed seedlings than in their unprimed counterparts. GPT activity decreased consistently with salinity and its values were lower on priming with GA₃. The activity of both enzymes increased with germination age. A new protein with MW of >97kD was detected in the primed seedlings treated with 200mM NaCl. A protein with MW of about 21.5 kD existed at all NaCl concentrations, increased with salinity, and its accumulation was greater with GA₃ priming.