Improved shoot development and rooting from mature cotyledons of sunflower

Regeneration and development of shoots from sunflower cotyledons were improved by optimizing explant age, plant growth regulator concentrations, and duration of exposure to plant growth regulators during shoot initiation, development and rooting. Shoot initiation required only a brief exposure to auxin and cytokinin, and minimizing the duration of exposure to high levels of 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-layer rooting medium.