Improved shoot development and rooting from mature cotyledons of sunflower

Regeneration and development of shoots from sunflower cotyledons were impro ved by optimizing explant age, plant growth regulator concentrations, and d uration of exposure to plant growth regulators during shoot initiation, dev elopment and rooting. Shoot initiation required only a brief exposure to au xin and cytokinin, and minimizing the duration of exposure to high levels o f plant growth regulators improved shoot development. Rooting was improved in terms of both the number of shoots that rooted and the time required for rooting by incorporating activated charcoal in the lower layer of a 2-laye r rooting medium.