Modelling parameters of maize growth in Marrakech.

摘要

The elongation dynamics of individual internodes and the panicle, ear and leaf area of maize were studied in the semi-arid conditions of Marrakech (Morocco) in a field experiment with the 16-leaf RAISA variety. Data for phytomer and organ extension and appearance were related to thermal time calculated from the base air temperature (10 degrees C). Using the approach of Fournier and Andrieu [3], we identified four stages: elongation was initially exponential during stage (I), and then increased sharply for a short period (stage II). A constant elongation rate defined stage (III), followed by stage (IV), during which the elongation rate decreased. Analysis of the regression coefficients showed that the mean relative elongation rate (RER) for phytomers did not differ significantly (P=0.05) between even (0.0181+or-0.00027) degrees C-1.d-1 and odd (0.0149+or-0.00058) degrees C-1.d-1 internodes. Stem and panicle extended similarly to even internodes (0.0179+or-0.0039) degrees C-1.d-1. The end of the exponential period for all phytomers was closely synchronized with the time the collar of this phytomer reached its surrounding ligules. The linear rates depended on the phytomer number, increasing from 0.0313 cm/ degrees Cd (internode 6) to 0.1188 cm/ degrees Cd (internode 9) and declining for the higher internodes. We identified two linear relations between linear rates and final lengths of all organs: the coefficient of proportionality was (0.0058+or-0.0003) per degrees Cd (R2=0.78) for all internodes and (0.0027+or-0.0005) per degrees Cd (R2=0.99) for other organs. The kinetics of internode extension was consistent with the results found by studies in Grignon (France) and in Gatton (Australia), although the rates of processes are different. They probably depend on the genotypic and experimental conditions and cultural practices. The priority for the plant for setting up its aerial organ, if we assume that the organ is in the linear growth phase, is first the leaf area, then the panicle, the stem and finally the ears. The highest ear is the last to begin its linear growth, but grows at a rate 1.5 times higher than that of the bottom ears. Moreover, the top ear enters its linear phase as the same time as the linear rates of the internodes (which have a relatively long extension period) begin to slow..