Influence of Ethylene Inhibitor Silver Nitrate on Direct Shoot Regeneration from in Vitro Raised Shoot Tip Explants of Sphaeranthus indicus Linn.—An Important Antijaundice Medicinal Plant

In the present investigation, an attempt has been made to study the influence of ethylene inhibitor silver nitrate on direct shoot regeneration in Sphaeranthus indicus, an important antijaundice medicinal plant, by using in vitro raised shoot tip explants. The effect of various concentrations of kinetin, BAP (0.5 - 3.0 mg/l), and NAA (0.1 - 0.5 mg/l) along with AgNO3 (0.1 - 1.0 mg/l) was studied. Among the combinations tested MS medium augmented with kinetin (1.0 mg/l), NAA (0.1 mg/l) and AgNO3 (0.4 mg/l) was found to be optimum for production of multiple shoots (34.3 ± 0.36). Addition of AgNO3 to the media not only increases shoot number in all the concentrations tested but also shoot length. AgNO3 at the concentration of 0.4 mg/l produced 35% more number of multiple shoots when compared to multiple shoots (10.8 ± 0.12) produced in control. In the present study by the addition of ethylene inhibitor silver nitrate and growth regulators, more number of multiple shoots (three folds) and shoot length was observed compared to control. These in vitro raised shoots were transferred to the rooting medium containing different concentrations of auxins such as NAA and IAA along with AgNO3 (0.1 - 0.6 mg/l). Better rooting response (21.6) was observed on NAA (2.0 mg/l) and AgNO3 (0.4 mg/l) containing media. The healthy rooted plantlets were transferred to polybags containing soil and vermiculate in 1:1 ratio for hardening. Finally the hardened plants were transferred to field environment for utmost survivability.

Functional mechanism study of the allelochemical myrigalone A identifies a group of ultrapotent inhibitors of ethylene biosynthesis in plants

Allelochemicals represent a class of natural products released by plants as root,leaf,and fruit exudates that interfere with the growth and survival of neighboring plants.Understanding how allelochemicals function to regulate plant responses may provide valuable new approaches to better control plant function.One such allelochemical,Myrigalone A(MyA)produced by Myrica gale,inhibits seed germination and seedling growth through an unknown mechanism.Here,we investigate MyA using the tractable modelDictyostelium discoideum and reveal that its activity depends on the conserved homolog of the plant ethylenesynthesis protein 1-aminocyclopropane-1-carboxylic acid oxidase(ACO).Furthermore,in silico modeling predicts the direct binding of MyA to ACO within the catalytic pocket.In D.discoideum,ablation of ACO mimics the MyA-dependent developmental delay,which is partially restored by exogenous ethylene,and MyA reduces ethylene production.In Arabidopsis thaliana,MyA treatment delays seed germination,and this effect is rescued by exogenous ethylene.It also mimics the effect of established ACO inhibitors on root and hypocotyl extension,blocks ethylenedependent root hair production,and reduces ethylene production.Finally,in silico binding analyses identify a rangeof highlypotentethylene inhibitorsthatblock ethylene-dependent responseand reduce ethyleneproduction in Arabidopsis.Thus,we demonstrate a molecular mechanism by which the allelochemical MyA reduces ethylene biosynthesis and identify a range of ultrapotent inhibitors of ethylene-regulated responses.

Role of Silver Nitrate on in Vitro Flowering and Shoot Regeneration of Solanum nigrum (L.)—An Important Multipurpose Medicinal Plant

Silver nitrate induced MS media enhanced multiple shoot regeneration and in vitro flowering from axillary bud and leaf explants of Solanum nigrum (L.) an important antiulcer medicinal plant. Healthy axillary bud and leaf explants were inoculated on MS medium supplemented with BAP/Kn (1.0 - 2.0 mg/l) in combination with IAA/NAA (0.5 mg/l) and AgNO3 (0.1 - 1.0 mg/l). The explants were responded effectively and good regeneration frequencies were observed in all the combinations of silver nitrate tested when compared to control. Maximum number of multiple shoots (34.3) was found in leaf explants cultured on MS media supplemented with BAP (2.0 mg/l), NAA (0.5 mg/l) and AgNO3 (0.4 mg/l). These regenerated shoots were sub-cultured on to the flowering media. Maximum number of in vitro flowers (12) was obtained from axillary bud explants in BAP (2.0 mg/l), Kn (1.0 mg/l), IAA (0.5 mg/l) and AgNO3 (6.0 mg/l) supplemented media when compared to leaf (4) and control. All the in vitro raised shoots were transferred to rooting medium supplemented with NAA, IBA (1.0 - 2.0 mg/l) and AgNO3 (0.1 - 0.6 mg/l). The best rooting response (24.6) was observed in 2.0 mg/l IBA + 0.4 mg/l AgNO3. The well rooted plantlets were transferred to polybags containing soil + vermiculate in 1:1 ratio for hardening and finally the hardened plantlets were transferred to field conditions.