Effects Of Water Stress On Grain Yield And Starch Physicochemical Properties Of Waxy Maize

The effects of water stress (drought and waterlogging) before and after pollination (tasseling silking stage and grain formation stage) and different drought degrees at grain formation stage on grain yield and starch physicochemical properties of waxy maize were studied using Suyunuo5 and Yunuo7 as materials in farm of Agricultural college, Yangzhou University in 2014-2015. The soil moisture content was controlled by negative pressure water supplying and controlling pot device. The main results were as follows:1. Effects of water stress before and after pollination on grain yield and starch physicochemical properties of waxy maizeWater stress (drought and waterlogging) during tasseling silking stage and grain formation stage decreased the grain number and reduced grain weight, led to grain yield loss. Water stress increased the grain soluble sugar content and decreased starch content, while protein content was increased and decreased under drought and waterlogging treatments, respectively.The starch granule size of waxy maize were increased and decreased by water stress at tasseling silking stage and grain formation stage, respectively. Starch iodine binding capacity was increased under drought and decreased under waterlogging conditions, respectively. Water stress had no influence on the crystalline type of waxy maize starch, the crystallinity of Suyunuo5 under spring sowing conditions was decreased by water stress, while the value for Yunuo7 in 2015 was only increased by waterlogging at grain formation stage and not affected by other water stress treatments.Except for pasting temperature, the other pasting characteristics of waxy maize flour were decreased by water stress and the decrease were severe when plants suffered drought at grain formation stage. The peak viscosity and breakdown of waxy maize were increased by waterlogging at grain formation stage and decreased by the other water stress treatments. The flour gelatinization enthalpy, onset temperature and retrogradation enthalpy were little affected by water stress. Peak temperature was not affected by drought at grain formation stage and was decreased by other water stress treatments, while conclusion temperature was only decreased by waterlogging at grain formation stage. The retrogradation percentage was only decreased by waterlogging at tasseling silking stage and was not affected by other water stress treatments. The starch gelatinization enthalpy was only increased by drought at grain formation stage and not affected by other water stress treatments. Peak temperature of waxy maize starch was not affected by drought during grain formation and reduced by other water stress conditions, while retrogradation enthalpy and percentage were increased by water stress.2. Effects of different drought degrees on grain yield and starch physicochemical properties of waxy maizeWith aggravated of drought degrees, the grain weight, number and yield gradually decreased. Drought increased the grain protein and soluble sugar content and reduced starch content, respectively. The grain glutelin content was decreased by drought, while albumin, prolamin and globulin content were increased by drought.The starch granule average size was increased by severe drought treatment and decreased by moderate drought treatment, respectively. The starch iodine binding capacity was decreased by drought at grain formation stage and the decrease was severe under mild drought treatment. Crystallinity of the starch under the spring and summer sowing dates in response to drought degrees was different. Crystallinity of Suyunuo5 under spring sowing treatment was only increased by severe drought, while the value in summer sowing conditions was increased with the severe of drought degrees. The crystallinity of Yunuo 7 was only increased by severe drought treatment under spring sowing conditions. The starch chain-length distribution in response to drought was dependent on sowing dates and the proportion of short chains in amylopectin was high under summer sowing conditions compared to spring sowing.The flour viscosities were decreased by drought. The starch peak, trough and breakdown viscosities were decreased by moderate and severe drought degrees, while pasting temperature was only decreased by mild drought, respectively. The flour gelatinization enthalpy, onset and conclusion temperature were similar among different treatments, while the retrogradation enthalpy and percentage was decreased by drought, and the decrease were severe with aggravate of drought degree. The starch gelatinization enthalpy was increased by severe drought; onset and peak temperature was decreased by all drought treatments, while conclusion temperature, retrogradation enthalpy and percentage were increased by drought.3. Correlations among different physicochemical characteristicsThe results of correlation analysis indicated that grain protein content was negatively correlated to waxy maize flour viscosity value (peak viscosity, trough viscosity and final viscosity), breakdown, setback and starch average granule size. The starch content was negatively correlated to pasting viscosity, pasting temperature, peak temperature, conclusion temperature, iodine binding capacity, crystallinity, gelatinization enthalpy, onset temperature, and retrogradation enthalpy. The soluble sugar content was positively correlated to starch crystallinity and negatively correlated to trough viscosity, final viscosity, setback, peak temperature, retrogradation enthalpy, retrogradation percentage, gelatinization enthalpy, conclusion temperature and iodine binding capacity. Iodine binding capacity was positively correlated to the proportion of long chains in amylopectin, pasting and gelatinization temperatures and retrogradation enthalpy. The starch granule size was positively correlated tostarch peak viscosity, final viscosity, trough viscosity, pasting temperature, peak temperature, and conclusion temperature. The proportion of long chains in amylopectin was positively correlated to pasting and gelatinization temperatures and retrogradation percentage, and it was negatively correlated to gelatinization enthalpy. The starch crystallinity was positively correlated to pasting temperature, onset temperature, peak temperature and setback, and negatively correlated to final viscosity, setback, conclusion temperature and gelatinization enthalpy.