Ethylene inhibitors promote in vitro regeneration of cowpea (Vigna unguiculata L.)

Ethylene is a plant growth regulator that is known to influence in vitro morphogenesis. This study investigated the effects of three ethylene inhibitors, silver nitrate (AgNO3), 2,5-norbornadiene, and cobalt chloride (CoCl2), on the regeneration of cowpea from cotyledon expiants. Significant increases in the percentage of regeneration occurred as a result of adding either$50 \mu M AgNO_3$or$100 \mu M 2,5-norbornadiene$. The number of shoots produced per expiant was enhanced by adding$25 \mu M CoCl_2$or 100 μ M norbornadiene. Maximum shoot elongation was obtained with 25 μ M of either CoCl2or norbornadiene. The effect of the duration of exposure to AgNO3was also determined. The greatest percent regeneration was obtained with the addition of$60 \mu M AgNO_3$either to both the initiation and regeneration stages, or to only the regeneration stage. The promotive effects on organogenesis in response to ethylene inhibitors suggests an important role for ethylene in the process of in vitro morphogenesis of cowpea and may contribute to its normally low regeneration frequency.