Growth, plastochron, and the final number of nodes of China pink seedlings grown on different substrates

Resumo

The objective of this work was to plot the growth curves and determine the plastochron and the final number of
nodes of China pink seedlings grown on different substrates. Thus, 392 China pink seedlings were grown on seven
substrates under greenhouse conditions, in Santa Maria in the state of Rio Grande do Sul, Brazil. The growth curves
were plotted using the logistic model. The plastochron was estimated by the inverse of the angular coefficient of the
simple linear regression between the number of accumulated nodes and accumulated thermal sum from the subsampling
of the seedlings. In all substrates, the logistic model fit better for the variable number of leaves than for the plant height.
The plants in substrates with 50% of soil plus 50% of rice husk ash, and 80% of rice husk ash plus 20% earthworm humus
had the longest cycles with 74 and 65 days, respectively. They completed the cycles with a thermal sum of 1317.9 ºC day
for number of leaves and plant height. The growth curves that were plotted by the logistic model and the plastochron of
the China pink seedlings are dependent on the type of substrate used. The commercial substrate Mecplant® had the best
results. The average final number of nodes of the main stem of the plants was 14 for all substrates.