Does thermal time for germination vary among populations of a tree legume (Peltophorum dubium)?

Abstract

Few works report the use of degree-days (DD) -used in crops to predict events and schedule management activities -to describe the germination of tropical trees. The cardinal temperatures (base, optimum and ceiling temperature) for germination of the species may vary depending on the seed provenance. Peltophorum dubium (Spreng.) Taub. is an early successional leguminous tree widely distributed in South America, often occurring as cultivated or naturalized trees, thus considered to be a good example for testing DD model in tree species. The main objective of this study was to describe the seed germination response of different populations of P. dubium as function of DD accumulation during germination assays in semi-controlled (fluctuating temperatures) conditions. Germination assays with manually scarified seeds sown in aluminum sheet trays filled with a composed substrate were performed under greenhouse conditions at different times. Three methods were employed in order to describe the accumulation of thermal time throughout the assays and, considering the seed lot and sowing time, a trapezoid area method was relatively more effective in describing the germination. The germination curves of P. dubium seeds from different populations, expressed in degree-days estimated directly from temperature records schedules, tend to be more clustered suggesting little variation among thermal time requirements in different seed provenances. Otherwise, the thermal time requirement can vary depending on the time of sowing, and any increase in DD requirement when the assays were performed under higher mean temperatures can be related to a thermal effect on the germination of scarified seeds.Keywords: degree-day, Fabaceae (Leguminosae), seed, canafístula. O tempo térmico para germinação varia entre populações de uma leguminosa arbórea (Peltophorum dubium)?Resumo O uso de graus-dia -utilizado em espécies cultivadas para predizer eventos e planejar ações de manejo -é reportado em poucos trabalhos para descrever a germinação de árvores tropicais. As temperaturas cardeais (base, ótima e teto) para germinação de uma espécie pode variar de acordo com a procedência das sementes. Peltophorum dubium (Spreng.) Taub. é uma leguminosa arbórea de sucessão inicial amplamente distribuída na América do Sul, podendo ocorrer como espécie cultivada ou naturalizada, sendo considerada um bom exemplo para testar modelos de graus-dia em espécie arbórea. O principal objetivo deste estudo foi descrever a resposta da germinação das sementes de diferentes populações de P. dubium como função do acúmulo de graus-dia durante ensaios em condições semi-controladas (flutuação térmica). Testes de germinação com sementes escarificadas manualmente e semeadas em bandejas de alumínio contendo substrato foram realizados sob condições de casa de vegetação em diferentes épocas do ano. Três métodos foram utilizados para descrever o acúmulo de tempo térmico nos ensaios e, considerando o lote das sementes e a época da semeadura, o método da área do trapézio foi rela...

A comparative study of the thermal ranges of three germination criteria of a tropical tree with bioeconomic interest: Carapa surinamensis Miq. (Meliaceae)

“…In the vast literature on seed germination temperature (Brancalion et al, 2010;Ferraz and Calvi, 2011;Dürr et al, 2015;Ribeiro and Costa, 2015;Andrade and Cardoso, 2016), only radicle protrusion has been assessed, and few studies evaluate more than one Stage of development. In this study the three developmental Stages of C. surinamensis differed in their thermal tolerance primarily involving the upper temperature limit.…”