Initial wall formation in the endosperm of wheat, Triticum aestivum: a reevaluation

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Abstract
Contrary to previous studies, cytokinesis has been observed on formation of the 1st anticlinal walls during initial cellularization in the endosperm of wheat. Typical phragmoplasts develop between the free nuclei in the peripheral cytoplasm, and the cell plates arising from these soon fuse with the wall of the central cell. The inner free margin of the walls, however, continues to grow towards the central vacuole within an advancing front of cytoplasm. Anticlinal walls arise around nuclei approximately simultaneously in different planes; 3 dimensionally the nuclei, therefore, become located within open-ended compartments of cytoplasm. The compartments then undergo cell division and develop periclinal walls by normal cytokinesis. These walls delimit the first complete layer of endosperm cells centrifugally and a new layer of open compartments centripetally. The inner compartments usually continue to grow centripetally until those from the opposite side of the grain meet. During this closing phase, along the zone where the compartments fuse, a further row of periclinal walls is formed. Subsequent immediate differentiation of endosperm involves the subdivision of the 1st-formed large endosperm cells into smaller cells.