A fern from a garden cultivation whose botanical characteristics refer to Nephrolepis cordifolia (L.) C. Presl (Cl. Polypodiopsida, Ord. Polypodiales, Fam. Nephrolepiadaceae)1 showing widespread leaf abnormalities was found in Campania Region (South Italy). No indications were available about environmental conditions and anthropic manipulations that may have caused the onset of the phenomenon and about the primary origin of the plant source. In the aerial part of the plant (Figure 1), the tips of most of the pinnae in the apical part of the fronds display a ‘wavy shape’ that evolves as a typical secondary frond when the tip of the mother frond unrolls and the lateral young pinnae become mature pinnae located in the middle of the mother frond itself (Figure 2, Figure 3, Figure 4). The secondary frond, i.e. the ‘pinna-derived frond’ (PdF), replicates the mother frond morphology, bearing typical secondary pinnae and crosiers. The secondary fronds reach a smaller size compared to the mother fronds they derive from, nevertheless they generate sori in the same period as the primary pinnae (Figure 5). The PdF is emitted only by the primary pinna tip (Figure 6), since emission has never been observed from the rachis as well as from secondary pinnae tips. The PdF emission is evident in most of the fronds and occurs throughout the growing period of the aerial part. No detectable abnormalities are evident in stems, runners, rhizomes and tubers. The PdF emission has so far been a stable feature, occurring every year in the new fronds emitted after the old ones had withered during the adverse seasons. Further, emission of the secondary fronds takes regularly place in new plants propagated from the original individual. No emission of PdFs has so far been observed in common N. cordifolia plants grown near the aberrant one. To the best of the author’s knowledge, a very similar phenotype was reported in the past in N. exaltata var. bostoniensis23, in which, however, the occurrence of the wavy pinnae morphology, that is the first stage of the secondary frond emission, was not clearly described. The phenotype reported in the present paper is different from the ‘crested fronds’ occurring in Athyrium angustum var. cristatum4, in which the whole pinnae are transformed in a new fronds. The phenotype described here also differs from the ‘forking leaves’ phenotype so far described in several fern species not belonging to the genus Nephrolepis, that occurs randomly among fronds and plants and at any level of the pinna lamina5. The PdF phenotype represents a plastic demonstration of the totipotency of the pinna apex, that can generate a fully developed frond while preserving the pinna structure in its basal part (Figure 6). This phenotype indicates that an alteration in the apical meristem activity in the pinna may trigger the generation of a primary organ from the apex of a secondary organ. This phenotype can be of great interest in investigations about the mechanisms underlying leaf morphological plasticity in plants, taking advantage of the presence of all the stages of the phenomenon at the same moment in the same genotype. The stability of the phenotype expression in the aerial part of the plant during the growing season and its recurrence in propagated plants, are also remarkable features that can be useful for scientific investigations.

The author received no funding for the submitted work. The author declares no conflict of interests.