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Evolution of root apical meristem structures in vascular plants: plasmodesmatal networks
Author(s) -
Imaichi Ryoko,
Moritoki Nobuko,
Solvang Hiroko Kato
Publication year - 2018
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/ajb2.1153
Subject(s) - meristem , apical cell , biology , plasmodesma , botany , root cap , shoot , ultrastructure , cell , genetics
Premise of the study The apical meristem generates indeterminate apical growth of the stem and root of vascular plants. Our previous examination showed that shoot apical meristems ( SAM s) can be classified into two types based on plasmodesmatal networks ( PN s), which are important elements in symplasmic signaling pathways within the apical meristem. Here, we examined the PN s of root apical meristems ( RAM s) in comparison with those of SAM s. Methods Root apical meristems of 18 families and 22 species of lycophytes and euphyllophytes were analyzed. Plasmodesmata ( PD ) in cell walls in median longitudinal sections of RAM s were enumerated using transmission electron micrographs, and the PD density per 1 μm 2 of each cell wall was calculated. Key results Root apical meristems with prominent apical cells of monilophytes (euphyllophytes) and Selaginellaceae (lycophytes) had high PD densities, while RAM s with plural initial cells of gymnosperms and angiosperms (euphyllophytes), and of Lycopodiaceae and Isoetaceae (lycophytes) had low PD densities. This correlation between structures of apical meristems and PD densities is identical to that in SAM s already described. Conclusions Irrespective of their diversified structures, the RAM s of vascular plants can be classified into two types with respect to PN s: the fern (monilophyte) type, which has a lineage‐specific PN with only primary PD , and the seed‐plant type, which has an interspecific PN with secondary PD in addition to primary PD . PN s may have played a key role in the evolution of apical meristems in vascular plants.