Are the three layers(dermatogen, periblem, plerome) in Histogen theory the same for root apex and shoot apex? 

Please find below the solution to the asked query

The Histogen theory proposed by Hanstein in 1870 explains that root and shoot apex consists of three types of tissue layers- dermatogen, periblem, plerome. 

However, this theory is true only for root apex and not for shoot apex of higher plants. In most of the higher plants-gymnosperms and angiosperms, shoot apex does not posses distinct differentiation of these three layers.

Hope this information will clear your doubts about the Histogen theory.
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