Dynamics of Assimilate Translocation and Its Contribution to Maize Kernel Exposed to Different Periods of Water Deficit

Abstract

Field experiment I was conducted under moderate water deficit conditions at four different growth stages (V10 to V13, V13 to V17, V17 to blister and blister to physiological stage) with three maize genotypes (Pioneer 30B80, NK 40 and Suwan 4452) and field experiment II was conducted under severe water deficit conditions at three stages (V10 to anthesis, anthesis to milk and milk to physiological maturity stage) with two genotypes (NK 40 and Suwan 4452) to evaluate the hypothesis that the translocation of stored stem reserves into the growing grain is an important source of carbon for supporting grain filling under water deficit. Significantly higher assimilate translocation, assimilate translocation efficiency and contribution of pre-anthesis assimilates to the grain were achieved in the V17 to blister stage under moderate water deficit and in the milk to physiological maturity stage under severe water deficit, respectively, with maximum stem dry weight depletion and stem dry weight depletion coefficients. NK 40 always sustained a smaller reduction in grain weight under both experiments. During grain filling, NK 40 exported 43.51 and 28.38% higher stem reserve dry matter compared to Pioneer 30B80 and Suwan 4452 under moderate water deficit conditions and a 46.20% higher stem reserve contribution compared to Suwan 4452 under severe water deficit conditions. Assimilate translocation in the two experiments showed a significant positive relationship with stem dry weight depletion (R2 = 0.81 and 87, respectively) and specific leaf weight depletion (R2 = 0.93 and 88, respectively), whereas it showed a significant negative relationship with the source-sink ratio (R2 = -0.53 and -0.84, respectively) and chlorophyll content (R2 = -0.50 and -0.63, respectively).