Figure legends
Figure 1. Kernel number per ear (KN/ear, A), thousand kernel weight (TKW, B) and yield (C) of different three maize line groups Te, Tr and Te×Tr in six different environments. Te – temperate inbred lines (n=40), Tr – tropical inbred lines (n=45), Te×Tr – subtropical inbred lines (n=77). Normal – maize growth period in normal temperature range, HDF – maize plants were subjected to heat stress during flowering, HEGF – maize plants were subjected to heat stress at early grain filling stage. Values with the same letter are not significantly different at P<0.05, comparison within the same sowing date only.
Figure 2. Correlations of yield, kernel number per ear (KN/ear), thousand kernel weight (TKW), daily maximum temperature (DMT, ℃), sunshine hours (SH, h) and rainfall (RF, mm) during the 15 days bracketing the silking stage in three inbred line groups (A, Te; B, Tr; C, Te×Tr). Te – temperate inbred lines (n=40), Tr – tropical inbred lines (n=45), Te×Tr – subtropical inbred lines (n=77). *** indicates significance at P < 0.001.
Figure 3. The kernel number reduction (KNR) of different three maize lines (Te – temperate, Tr – tropical, and Te×Tr – subtropical) in two sowing dates (Mar.21 and Apr. 28 in 2015; Mar. 21 and May 24 in 2016). The horizontal line represents the mean value of kernel number reduction within the same maize inbred line group with the same genetic background. * indicates significance at P < 0.05.
Figure 4. The killing degree days (KDD, ℃) of three maize inbred line groups (Te – temperate, Tr – tropical, and Te×Tr – subtropical) in two sowing dates (Mar. 21 and Apr. 28 in 2015; Mar. 21 and May 24 2016). The KDD represents the sum of the daily maximum temperature above 28 ℃ during the entire growth season. Values with the same letter are not significantly different at P<0.05, comparison within the same sowing date only. ** indicates significance at P < 0.01.
Figure 5. The correlation between kernel number per ear (KN/ear) and killing degree days (KDD, ℃) of Te (n = 80), Tr (n = 90), and Te×Tr groups (n = 154), in the first (A) and second (B) sowing dates in 2015 and 2016. * indicates high signification at P < 0.05.
Figure 6. Flowering dynamics in different maize lines (n=162) as effect of sowing date and year, including point-in-time (days after sowing, DAS) of Tasseling, pollen shedding, silking, and time periods (days) of anthesis-silking interval (ASI). These maize lines were classified into three groups, temperate inbred lines (Te, n=40), tropical inbred lines(Tr, n=45), subtropical inbred lines (Te×Tr, n=77). Values with the same letter are not significantly different at P < 0.05, comparison within the same sowing date only.
Figure 7. The advance in tasseling time (TT), pollen shedding time (PST) and silking time (ST) for three maize line groups (Te, Tr, Te×Tr) from the first to the second sowing date in 2015. Values with the same letter are not significantly different at P<0.05, comparison within the same flowering trait only.
Figure 8. The correlation coefficients of kernel number per ear at maturity stage with point-in-time (days after sowing, DAS) of tasseling, pollen shedding, silking, and anthesis-silking interval (ASI). Te – temperate inbred lines (n=40), Tr – tropical inbred lines (n=45), Te×Tr – subtropical inbred lines (n=77). * indicates significance at P < 0.05.
Figure 9. The correlation coefficients of kernel number per ear (KN/ear, A), thousand kernel weight (TKW, B), and grain yield (C) with average daily maximum temperatures before, during, and after flowering stages for three maize line groups Te, Tr and Te×Tr. Te – temperate inbred lines (n=40), Tr – tropical inbred lines (n=45), Te×Tr – subtropical inbred lines (n=77). * indicates significance at P < 0.05.
Figure 10. The relative contributions of inbred line, sowing date, and the residual factors to kernel number per ear (KN/ear), thousand kernel weight (TKW), and grain yield of temperate (Te, A1 – C1), tropical (Tr, A2 – C2), and Te×Tr maize (A3 – C3).