Filling in the gaps: evidence of leaf endodermis and vein sheath in gymnosperms

Endodermis with Casparian bands is only characteristic of most species of Pinaceae; vein sheaths are found in three genera of Pinaceae and six genera of the other families of gymnosperms, but most gymnospermous leaves lack endodermis and vein sheath, particularly in petiolar and leaf base regions. The presence of endodermis with Casparian bands could have contributed to the adaptation of the Pinaceae to extreme environments; members of genera such as Picea and Pinus are the typical treeline species in many mountain ranges across the world.