Stimulatory and period-specific effect of nitric oxide on in vitro caulogenesis in Albizzia lebbeck (L.) Benth.

The paper reports stimulatory effect of nitric oxide (NO) on in vitro caulogenesis in Albizzia lebbeck, a tree legume. Exogenously supplied NO donor, sodium nitroprusside (SNP) stimulated shoot differentiation from hypocotyl explants of Albizzia lebbeck, excised from its in vitro seedlings. Potassium ferrocyanide, a structural analog of SNP incapable of releasing NO, did not promote shoot organogenesis. Likewise, metabolic products of NO, NO2 (-) and NO3 (-), provided as NaNO2 and NaNO3 did not enhance shoot differentiation. The NO scavenger, 2-(4-carboxy-phenyl)-4, 4, 5, 5-tetramethylimideazoline-1-oxyl-3-oxide (cPTIO), supplemented along with SNP, at equimolar concentration, reversed the stimulatory effect of the latter, thus, confirming the role of NO in promotion of in vitro caulogenesis. The transfer of explants cultured on the basal medium (BM) to the same containing SNP and vice versa after different time intervals revealed that for its enhancing effect, SNP was required only during the initial phase (5 days) of culture. Its presence or administration beyond 5 days neither promoted nor inhibited the caulogenic response.