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Table 1 The anatomical structure of six Wolffia species

From: Frond architecture of the rootless duckweed Wolffia globosa

  Wolffia arrhiza Wolffia columbiana Wolffia borealis Wolffia australiana Wolffia globosa Wolffia microscopia
Epidermis A single epidermal layer with chloroplasts A single epidermal layer with chloroplasts A single epidermal layer with chloroplasts A single epidermal layer with chloroplasts A single epidermal layer with chloroplasts The upper single epidermis almost completely lacks chloroplasts
Stomata 40–50 More than 40 314.34 ± 46.99 /mm2 Two to three rows of stomata in the dorsal surface
Mesophyll The upper palisade-like cells subjacent to the lower vacuolated cells A single mesophyll cell size and type Vary in size from small cells toward the dorsum to large cells toward ventrum The upper third was loosely packed palisade-like parenchyma cells, the lower two thirds were composed of large, highly vacuolated cells Vary in size from small and dense palisade-like parenchyma cells in dorsum to large and empty vacuolated cells in ventrum Centre composed of loosely arranged parenchymatic cells interspersed with air spaces towards the dorsal side and more tightly packed parenchymatous cells with small air spaces towards the ventral surface
Chloroplasts Concentrated in epidermis, mesophyll cells and vaculated cells Mainly concentrated in epidermis Concentrated in dorsal mesophyll cells Concentrated in dorsal mesophyll cells Both in the mesophyll cells and epidermis Prominent in the lower epidermis and ventral parenchymatic cell layers
Transfer cells Present in the epidermis Absent Present in adjacent mature mesophyll cell
Pseudoroot Absent Absent Absent Absent Absent Present
Reference [15] [17] [17];
[18]
[16] Current study [19]