Effect of Gibberellin and Uniconazole on Mesocotyl Elongation of Dark-Grown Maize under Different Seeding Depths

Abstract

Seeds of five maize inbred lines, including 3681-4, were treated with gibberellin A3 (GA3) and uniconazole (UCZ) under deep seeding and shallow seeding in order to elucidate the physiological mechanism of maize mesocotyl elongation under different seeding depths. GA3 was the most effective at 10-5 M and the mesocotyl elongation of 3681-4, 178, Zong 3, Huang C, Han 21 was promoted at this concentration by 60.4%, 44.6%, 42.5%, 24.2% and 44.2% under 20 cm seeding depth, respectively. Under 2 cm seeding depth, however, there were no significant differences between mesocotyl length of all inbred lines at any concentration. UCZ treatment at concentrations higher than 10-5 M, significantly inhibited mesocotyl elongation in all inbred lines under seeding depths of both 20 cm and 2 cm. Interestingly, mesocotyl elongation of only 3681-4 was significantly inhibited at the concentration of 10-7 M. These results suggested that mesocotyl elongation was more sensitive to gibberellin A (GA) under deep seeding than under shallow seeding, and that 3681-4 was more sensitive to GA than the other inbred lines. Endogenous gibberellin A1 (GA1) contents in the mesocotyls of 3681-4 and 178 treated with GA3 and UCZ were accordant with their morphological responses. GA3 promoted cell elongation rather than cell division, and that UCZ inhibited both cell elongation and cell division in 3681-4 and 178.