The phyllochron is defined as the time needed for appearance of successive leaves on a culm in plants of the Poaceae family. Using the concept of phyllochron, it is possible to calculate the number of accumulated leaves, which is an excellent parameter to measure the plant development. The objective of this study was to estimate the phyllochron of seven rice cultivars grown in Southern Brazil in five sowing dates in the Central Region of Rio Grande do Sul State. A two-year field experiment was carried out in Santa Maria, RS, Brazil during 2003/2004 and 2004/2005 growing seasons, with five sowing dates each year. Seven rice cultivars recommended for Southern Brazil were used: IRGA 421, IRGA 416, IRGA 417, IRGA 420, BR-IRGA 409, BRS 7 TAIM and EPAGRI 109. The phyllochron (°C day leaf-1) was estimated by the inverse of the slope of the linear regression between main culm number of accumulated leaves (represented by the Haun Stage) and thermal time (base temperature = 11°C) accumulated from plant emergence. Genotype differences are small and can be neglected, but the environment, mainly through sowing date, has a large effect on phyllochron in rice.
Oryza sativa L.; leaf appearance; plant development; temperature
