De invloed der bemesting op het carotine- en vitamine C-gehalte van de plant
1936
IJdo, J.B.H.
For practical reasons Spinacia oleracea was chosen for these pot experiments in a greenhouse. For the quantitative estimation of carotene, a short method was developed. The vitamin C content of leaves decreased rapidly at room temperature and even at ice-box temperature, so analysis had to be rapid (titration with 2,6- dichlorophenolindophenol in acid medium).The pots contained pure washed quartz sand or an exactly analysed sandy soil, and were supplied with Krnger's nutrient solution.Increasing the N supply increased the carotene and vitamin C content. Increasing K supply decreased carotene content, but increased vitamin C content. But decrease in carotene content was only obvious in plants grown with little N. The increase of vitamin C content was usually most distinct in plants grown with much N, although it was fairly clear in the whole combined experiment. The influence of P, Ca and Mg salts was small.A final section attempts to interpret the data to demonstrate a relation between chlorophyll and carotene. Ascorbic acid was considered to be a product of photo- synthesis. This could explain the peculiar course of carotene and vitamin C contents with K fertilizers. K deficiency acted as a N excess, while K excess acted as N deficiency.
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