Table I.

Comparison of α- and β-expansins

Characteristic	α-Expansins	β-Expansins
No. of genes in Arabidopsis	≥16	≥1
No. of genes in rice	≥4	≥7
Activity in dicot walls	High^-a	Low^-b
Activity in grass walls	Low^-b	High^-b

↵F0-a Measured for α-expansins from cucumber, oat, maize, and rice.
↵F0-b Measured only with Zea m1.