27–10 Callus development E ffect of
increasing IAA concentration at different
kinetin levels on growth and organ formation
of tobacco (Nicotiana tabacum) callus cultured
on nutrient agar. Note that very little growth
occurred without the addition of either IAA
or kinetin (top left). Higher levels of IAA alone
(top rows) promoted root formation, whereas
higher IAA repressed bud formation when
used alone or in combination with kinetin
(right-hand columns). The higher level of
kinetin (lower rows) was more effective than
the lower level (middle rows) in promoting
bud development, but both kinetin levels
were too high for promotion of root growth.