1. Albert, L. S. 1965 Ribonucleic acid content, boron deficiency symptoms and elongation of tomato root tips. Plant Physiol.40, 649–654.
2. Arnon, D. I. and Hoagland, D. R. 1950 The water culture method for growing plants without soil. Calif. Agric. Exp. Stn. Circ.347.
3. Association of official Analytical Chemist 1975 Official methods of analysis. P.O. Box 540, Benjamin Franklin Station, Washington DC 20044.
4. Bar Akiva, A. and Sterbaun, S. 1965 Possible use of nitrate reductase activity of leaves as a measure of the nitrogen requirement of citrus trees. Plant Cell. Physiol.6, 575–577.
5. Cadahia, C.; Piñero, M. T. 1974 Determinación de glúcidos en plantas por fotocolorimetría. Estudio comparativo de métodos clásicos y automáticos. Anal. Edafol. Agrobiol.XXXIII, 9–10.