Abstract
This work was conducted in the Iapar Experimental Station at Londrina, state of Paraná, Brazil. Leaf, fruit peel and seed samples were collected in an experimental site of Coffea Arabica cultivars Mundo Novo, Catuaí, Icatu, Sarchimor and Laurina and of Coffea canephora, cultivar robusta. The objective was to save time in the plant selection with different caffeine content with previous determination of the alkaloid in the leaf. Samples composed by the first, third, and sixth pair of leaves counted from the lateral branch in the following coffee fruit stages: initial growth, fruit filling, green formed gram and full maturation. Fruit samples were collected in the bearing stage. Part of the fruits were sown to obtain seedlings from which were colleted the first and third pair of leaves. Plant materials were dried, ground and then used for the caffeine termination. Caffeine was extracted by the hot water method and determined by spectrophotometry at 273nm. The results showed that for the both coffee species the caffeine content in the first and third pair of leaves of the seedlings increased linearly with increasing caffeine content in the seeds of the plants from the same variety in the field. Therefore, the first and the third pair of leaves of the seedlings were considered to be efficient to estimate of the caffeine content in the seeds of the mature plants. Under field conditions the first pair of leaves showed caffeine content higher than older leaves, mainly for the Coffea canephora. Coffee fruit in the maturation stage presented the lowest caffeine content in the leaves. The first pair of leaves sampled in the beginning of fruit growth was the most efficient plant material to estimate the caffeine content in the seeds as compared with the older leaves and with the more advanced time of the fruit development. The alkaloid contents were slightly lower in the fruit peel (shell + parchment) as compared with seeds. The caffeine content in the seeds increased linearly with increasing N content
Highlights
A cafeína é um alcalóide, encontrado nas sementes de café, pertencente ao grupo das metilxantinas, que ocorre livre no citoplasma ou complexada com o ácido clorogênico na forma de sais de potássio (Horman e Viani, 1972)
A análise do teor de cafeína em folhas e em sementes de algumas cultivares de C. arabica e de C. canephora mostrou que a concentração de cafeína nas sementes aumentou linearmente com o aumento dos teores de cafeína nas folhas do primeiro par em mudas, conforme mostra a Figura 1 A
O teor de cafeína no sexto par de folhas da espécie C. canephora, em todas as épocas avaliadas, foi bem inferior em comparação com as cultivares do C. arabica, o que reforça a hipótese de redistribuição para os frutos, visto que as sementes de café daquela espécie acumulam muito mais cafeína comparativamente às cultivares de C. arabica
Summary
O trabalho foi realizado no Centro Experimental do Iapar em Londrina, Estado do Paraná, utilizandose de cafeeiros cultivados em experimentos do programa de melhoramento. Sendo as folhas colhidas em quatro diferentes estádios fenológicos: após o florescimento na fase de “chumbinho”, crescimento do fruto (expansão), granação do fruto e maturação do fruto (cereja); essas folhas foram retiradas do primeiro, do terceiro e do sexto pares (separadamente), a partir da extremidade superior do galho plagiotrópico, na altura média das plantas, coletando-se um par em cada quadrante, em 10 plantas de cada cultivar por repetição. A cafeína dos tecidos do cafeeiro (folha, palha e semente) foi extraída em água quente e determinada por espectrofotometria a 273 nm (Li et al, 1990). O procedimento constou do seguinte: preparo da solução padrão de cafeína em H2O 0,0; 10,0; 25,0; 50,0; 100,0 e 150,0mg L-1; transferência de 200,0 mg de amostra de tecido vegetal para frasco de vidro de 50,0mL; Adição de 20,0mL de H2O e 500,0mg de MgO; aquecimento por 30 minutos, em banho-maria, a 95oC, após temperatura ambiente, completou-se o volume de água evaporada. A interpretação dos resultados baseou-se nas análises de variância, procedendo-se também a análises de regressão para avaliação das relações entre os resultados da análise foliar e os valores de cafeína nas sementes
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