OCCURRENCE OF ENDODERMIS WITH A CASPARIAN STRIP IN STEM AND LEAF

It is well known that an endodermis with casparian strip always occurs in roots, but few people are aware that it also occurs in stems and l eaves of some vascular plants. The rather sparse literature on endoder mis in aerial organs was last included in a review in 1943. The presen t compilation, which does not consider hydathodes, nectaries, or other secretory structures, emphasizes distribution of cauline and foliar e ndodermis with casparian strip. It occurs unevenly among major taxa: q uite common in rhizomes and leaves among pteridophyte groups, with exc eptions; absent in gymnosperm stems but found in leaves at least among some conifers; in stems of at least 30 mostly herbaceous angiosperm f amilies, but far less common in leaves, where it is mostly reported fr om petioles. Etiolation can induce casparian strips in stems and petio les of some herbaceous plants, but results from leaf blades are questi onable. There are recent reports of an endodermis with casparian strip in leaves of both woody and herbaceous taxa The physiological functio n, if any, of a casparian strip in aerial organs remains unknown.