Table 1.

Effect of IbEXP1 down-regulation on cell proliferation activities in the fibrous root Data are means ±SD from three separate measurements of three sections from three individual plants and are collected from the in vitro cultured sweetpotato plants at 10 d after planting.

Cell type	Wild type	IbEXP1-antisense #1		IbEXP1-antisense #2
	No. of cellsa	No. of cells	Rate (fold)b	No. of cells	Rate (fold)
Cambium	46±6	94±5	(2.0)	64±7	(1.4)
Metaxylemc	30±4	73±2	(2.4)	60±1	(2.0)

^a Counted on transverse sections of fibrous roots.

^b Proliferation rate relative to that of wild-type plants.

^c Numbers of metaxylem cells, including mature and immature metaxylem cells.