Effects of conservation tillage on grain filling and hormonal changes in wheat under simulated rainfall conditions

The objective of this study was to investigate the effect of conservation tillage (CT) on wheat grain filling under different precipitation levels and the relationship with endogenous hormonal changes. In the present study, CT was compared to traditional bare soil tillage (BT) under different precipitation conditions simulated during the wheat growth stage, and the resulting hormonal changes in the grains were measured. The results indicated that the effect of CT on wheat grain filling is significantly related to precipitation. At the 220-mm rainfall level, CT significantly promoted grain filling of the superior and inferior grains. CT also significantly promoted the grain filling of inferior grains at 260-mm rainfall yet had no significant effect on filling of the superior grains. In contrast, CT had no significant effect on the grain-filling rates and grain weight of superior and inferior grains at the 300-mm rainfall level. At 220- and 260-mm rainfall, CT significantly increased the indole-3-acetic acid (IAA) and zeatin (Z) + zeatin riboside (ZR) contents and decreased the abscisic acid (ABA), ethylene (ETH), and gibberellic acid (GA) contents in the inferior grains, whereas CT only had these effects in the superior grains at the 220-mm rainfall level. The IM, ABA, and Z + ZR contents in the grains were positively and significantly correlated with the maximum grain weight and the maximum and mean grain-filling rates; the ETH concentration was negatively and significantly correlated with the maximum, grain weight and the maximum and mean grain-filling rates. In addition, both precipitation and CT significantly increased the soil moisture during the grain-filling stage. Based on these results, we conclude that the CT treatment significantly increased the soil moisture, thus regulating the grain filling of wheat, and that this process was significantly related to the balance of hormones in the grains. (C) 2013 Elsevier B.V. All rights reserved.