REGULATOR OF PLANT GROWTH

PROBLEM TO BE SOLVED: To obtain a regulator of plant growth substantially and hardly causing side effect such as epinasty of a leaf and having high activities for improving rooting of a plant by including a specific compound (salt) as an active ingredient. SOLUTION: The objective regulator contains a compound (salt) of formula I [Ar is a (substituted) phenyl; A is a lower alkylene; B is a lower alkylene or a lower alkynylene; R is OH, amino or a lower alkoxyl], e.g. 4-oxo-4[[2-(4- tryl)ethyl]amino]lactic acid} as an active ingredient. The compound of formula I is obtained, for example, by the method for reacting (A) a compound of formula II with (B) a compound of formula III in an molar ratio of the components A to B regulated so as to be (0.5-1.5):(1.5-0.5) in an inert medium at 0-60 deg.C for 10 min to 24 hr to provide a compound of formula IV. The regulator has activities for increasing the amount of roots, activities for inhibiting the extension of a stem, or the like and especially the use as a rooting-promoting agent is preferable.