The genetic control of the physiological determinants of grain yield is almost unknown. Canopy size and light interception efficiency are among these determinants, which includes the dynamics of leaf expansion and senescence. In this work we phenotyped a RILs family of 250 maize (Zea mays L.) inbreds derived from the IBM Syn4 population  (B73×Mo17), including parental inbreds. Experiments were grown in the field (31-33 ºS; 60-61 ºW) during three contrasting growing seasons (irrigated with no heat stress, irrigated with heat stress, and severe drought) in a completely randomized block design with two replicates. Seven plants were tagged at V3 on the central row of each plot to follow (i) the dynamics of leaf growth and senescence and fraction of light interception (fortnightly from V5 onwards), (ii) dates of 50% anthesis and silking, and (iii) grain yield and its determinants (seed number and individual seed weight). Individual leaf area was computed as lamina length × maximum width × 0.75. Leaf area index (LAI) was calculated as the product of leaf area per plant and number of plants per unit land. Genotypic variation was analyzed by a linear mixed model to estimate variance components for each measured trait. Broad sense heritability (h²) was estimated from the components of variance.