Effects of PP333 spraying on some physiological, morphological characteristics and yield of wheat on dryland with different plant density

A field experiment was conducted to study the effects of different concentration PP333, its spraying time and plant growing stages at which PP333 was sprayed, as well as a combination of PP333 and GA3 on some physiological, morphological characteristics and yields of dryland wheat. The experiment included two factors: plant density and spraying PP333. Two levels of the plant density were adopted: low density with sowing rate of 1670000 seeds, and high density with sowing rate of 3340000 seeds. The spraying of PP333 involved 5 treatments: 1) spraying water as control; 2) spraying PP333 at re-growth stage with low concentration (150 mg /kg) ; 3) spraying PP333 at re-growth stage with high concentration (300 mg/kg) ; 4) spraying PP333 at 3 leaf stage, re-growth stage and elongation stage with a concentration of 100 mg/kg; and 5) spraying PP333 at 3-leaf stage, re-growth stage and elongation stage with a concentration of 100 mg/kg and spraying CA3 (30mg/kg) at elongation stage together with PP333 by dissolving CA3 in the PP333 solution. Results show that application of PP333 significantly increased tiller numbers and reduced plant height and leaf area, the degree of reduction depending on concentrations and times: the higher the concentration and the more frequent the applications , the more reduction. In contrast, GA3 alleviated the effect of PP333 on the reduction. No difference was found in chlorophyll content at over-wintering stage for different treatments while the increase was observed at elongation stage by PP333 spraying. Although at elongation stage, no significant difference was found in NRA, NH4+-N and NO3--N content among different treatments, NRA was inhibited at over-wintering stage by PP333 spraying. Application of PP333 at the 3-leaf stage, followed by spraying PP333 and GA3 at elongation stage, although reducing grain number per ear, obviously increased the harvesting ear numbers and raised or retained the weight per 1000 grains, and thereby increased wheat yield by 5.8% . Application of PP333 alone showed no significant effect on crop yield. Different results obtained by spraying PP333 on wheat at different stages and with different plant densities might be related with water and nutrient supply of the soil.