Physiological Effect of Diphenylamin and Tryptophan on the Growth and Chemical Constituents of Philodendron erubescens Plants

A pot experiment was carried out in the nursery of the Ornamental Horticulture Department, Faculty of Agriculture, Cairo University, during the two successive seasons of 2003/2004 and 2004/2005, with the aim of studying the effect of foliar application of the amino acids diphenylamin and tryptophan (each at the rates of 50 or 100 ppm), applied separately or in combinations of the different concentrations (plus untreated control plants), on the growth and chemical constituents of Philodendron erubescens plants. The most important results can be summarized as: 1) Both diphenylamin and tryptophan significantly increased plant growth (in terms of plant height, number of leaves/plant, stem diameter, root length, leaf area, as well as fresh and dry weights of the different plant parts) and the contents of carotenoids, total soluble sugars and total free amino acids in the leaves. 2) The effect of diphenylamin was superior to that of tryptophan on increasing plant growth and chemical constituents. 3) In both seasons, the maximum plant growth (as determined by all the recorded parameters) was obtained from plants treated with diphenylamin at the rate of 100 ppm, followed by tryptophan at 100 ppm. 4) Amino acids treatments had no significant effect on the chlorophyll A and B contents in both seasons. However, the total chlorophyll content was significantly increased in the second seasons as a result of the amino acid treatments. 5) Plant treated with diphenylamin at 100 ppm had the highest contents of caroteniodes, total soluble sugars and total free amino acids in the leaves.