Ocorrência e superação da dormência em sementes de mamão (Carica papaya L.) em função da época de colheita dos frutos

• Autor(a) principal: Tokuhisa, Dai
• Data de Publicação: 2006
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/4460
• topic: Carica papaya; Sementes; Dormência; Carica papaya; Seeds; Dormancy; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOTECNIA

This work was carried out in the Laboratory of Seeds Analysis in the Department of Fitotecnia at Federal University of Viçosa from March 2004 to November 2005, in order to relate the harvest time of fruits with dormancy occurrence in papaya seeds and to define appropriate treatments to overcome dormancy of these seeds. Papaya fruits of the Formosa group, hybrid Tainung 01, supplied by the company Hera Sementes, Linhares ES. Brazil where used. The seeds were extracted from fruits harvested at five different times: July and November 2004, February, May and September 2005. At each harvest time, seed germination was evaluated at 15 and 30 days after seeding. Seeds without sarcotesta were treated as following: washing in running water for 2 and 4 hours, pre-drying to 40ºC/96h, pre-cooling to 10ºC/14 days, accelerated aging to 41ºC for 36, 48 and 72 h, immersion in NaOCl 0,5% for 1, 2, 3, 4 and 5 h, immersion in KNO3 1 M for 30, 60, 90 and 120 minutes, immersion in GA3 400, 600 and 800 ppm for 24 h, moistened germination paper with GA3 400, 600 and 800 ppm, storage of the seeds for 3, 6 and 9 months, and thermal shock to 15-35ºC. For phenolic compounds quantification in different structures of seeds (sarcotesta, esclerotesta, endosperm and embryo), tannic acid was used as standard and color reaction with Folin-Ciacalteau reagent was measured at 765 nm by spectrophotometry. A bioassay with lettuce seeds was performed to evaluate inhibition effect of papaya seed sarcotesta extract. This bioassay was performed in moistened germination paper having water as control. Seeds from fruits harvested at July 2004 and May 2005 were dormant, what didn't happen in the other harvest times. The best treatments for overcome dormancy in papaya seeds were the use of substratum moistened with GA3 600 ppm or the immersion of the seeds GA3 600 ppm for 24 hours and immersion of the seeds in KNO3 1M for 30, 60 and 90 minutes. High amount of phenolic substances was found in the papaya seeds esclerotesta, followed by the sarcotesta, being practically null the concentration of these compounds in the embryo and endosperm. Seeds extracted from fruits harvested on May 2005 had higher phenolics content compared with seeds harvested on September 2005. The bioassay indicated that sarcotesta extract inhibits the germination and the growth of the lettuce seedling primary roots due to the presence of inhibitory substances (phenols).