New approaches on source-sink relationships in maize: nitrogen accumulation during kernel development and effects on kernel weight

ROSARIO SARIC; HERNÁN DOMINGUEZ; DIEGO FANELLO; MARÍA L. MAYDUP; JUAN J. GUIAMET; MARIANA ANTONIETTA

Rosario

Congreso; XXXIV Reunión Argentina de Fisiología Vegetal; 2023

Asociación Argentina de Fisiología Vegetal

Traditional approaches on source-sink relationships in maize estimate the sink by the number of fixed kernels. However, recent works suggest that kernel nutrient status plays an important role determining sink strength. To explore this, a field experiment with two N levels (70 vs. 200 kg N ha-1) and four hybrids (SYN840 vs. SYN860, and DK72 vs. DK73) was conducted in La Plata, Buenos Aires, to compare kernel C and N accumulation during grain filling. Kernel samples were taken at 20, 38 and 60 days after silking (DAS). Yield was reduced by 38% at low N level, due to both reductions in kernel number (-25%) and kernel weight (-17%). Between hybrids, yield reduction was larger in SYN840 (-42%, vs. -35% in SYN860) and DK72 (-41% vs. -35% in DK73). Decreased N level significantly reduced kernel %N, with N x stage interaction showing lowest reductions at 60 DAS and hybrid x stage interaction indicating that hybrid differences were accentuated at early and mid-developmental stages. At 20 DAS, lowest %N was detected in SYN840 (1.23% vs. 1.38% in SYN860) and in DK72 (1.32 vs. 1.53%) whereas at 38 DAS the same trend was maintained (1.06% vs. 1.24% in SYN840 and SYN860; 0.96 VS. 1% in DK72 and DK73). The concentration of soluble sugars in kernels (a possible proxy of failures in C metabolism) was higher at low N, especially in SYN840 (+34% vs. -18% in SYN860) and DK72 (+11% vs. 3.6% in DK73). Across hybrids, yield was positively related to %N in kernels at stages I and II (r2=0.38*** and r2=0.60***, n=32). These results show that (i) %N in kernels at harvest is not a good proxy of N status during kernel development; (ii) hybrid trends in %N in kernels are not maintained across N levels; (iii) low %N in kernels at early stages of development relate to higher soluble sugar concentration. These results suggest that in some situations, %N in kernels could be below those required to optimize kernel carbon metabolism.