Rela？？o da leitura do clorofil？metro com os teores de clorofila extraível e de nitrogênio na folha de milho

the methods used to determine the amount of leaf chlorophyll require destruction of tissues samples and much work in the process of its attainment. the recnt development of the portable chlorophyll meter, that makes instantaneous readings of relative chlorophyll content in leaf, without necessity of leaf destruction, appears as a new technique to estimate this parameter. with the objectives to evaluate the relation between readings of portable chlorophyll meter with of extractable chlrophyll and nitrogen contents in the leaf in three development stages of plant maize and to validate the use of this equipment as a parameter to estimate chlorophyll relative content in leaf, an experiment was conducted in the state of rio grande do sul, brazil, in the 1999/2000 growing season. treatments consisted of two maize simple hybrids (pioneer 32r21 and premium) and eight nitrogen management systems. the readings with portable chlorophyll meter and the chlorophyll extration and nitrogen content determination in leaf were taken in the stages 6 to 7 leaves, 10 to 11 leaves and silking. in the two hybrids, the amounts of total chlorophyll and chlorophylls a and b were significantly related to the readings of portable chlorophyll meter, in the three development stages evaluated. the readings carried out with portable chlorophyll meter estimated with good accuracy the relative chlorophyll content in maize leaf. in addition, this method present the advantages to have higher performance, minor cost and not implying in leaf destruction. however, portable chlorophyll meter is not very accurate to evaluate n level in plant in initial stages of plant development (6 to 7 leaves).