Chemical stimulation of seed germination in Aconitum heterophyllum Wall. and A-balfourii Stapf.: Important Himalayan species of medicinal value

Aconitum heterophyllum Wall. and A. balfourii Stapf. are important medicina l herbs of the Himalayan region. The effect of plant growth substances (PGS s, namely, abscisic acid, 6-benzylaminopurine, gibberellic acid and zeatin riboside) and two nitrogenous compounds (thiourea and potassium nitrate) fo r enhancing and synchronising uniform germination was examined. The tetrazo lium (Tz) staining pattern indicated that freshly collected seeds had high viability which decreased following storage at 4 degrees C for 6 and 12 mon ths. The treatments and time of seed germination were found to be significa ntly different (P < 0.01). Gibberellic acid (GA,; 250 mu M) significantly e nhanced seed germination (42.5% compared to 27.5% in control) in A. balfour ii with in 15 weeks but was inhibitory in A. heterohyllum. 6-Benzylaminopur ine (BAP; 25 and 250 mu M) and zeatin riboside (ZR; 25 and 250 mu M) did no t enhance germination in A. balfourii; 250 mu M ZR was actually inhibitory. In A. heterophyllum the lower concentration of BAP was inhibitory (7.5% co mpared to 25.0% in control) while 250 mu M BAP enhanced germination (42.5% compared to 25.0% in control); the higher concentration of ZR was inhibitor y. The combined treatments of gibberellin and cytokinin in general resulted in reduced germination in both species. Among the nitrogenous compounds, t hiourea (CH4N2S) increased the rate and germination percentage in both spec ies but potassium nitrate (KNO3) enhanced germination in A. balfourii only. Seed germination was first detected in A. balfourii in the 5th week (2.5%) following treatment with 65 mM CH4N2S acid this value increased to 22.5% i n the 7th week and reached as high as 75% (compared to 27.5% in control) in the 15th week. A higher dose of thiourea (130 mM) resulted in a rapid and high germination rate (40% compared to 0% in control) in the 7th week, reac hing 75% in 10th and 12th weeks and a maximum 80% (compared to 27.5% in con trol) in the 15th week. In A. heterophyllum, however, thiourea only margina lly enhanced germination even up to the 15th week. In A. balfourii, KNO3 (5 0 and 100 mM) significantly enhanced germination (62-70%) within 15 weeks.