Effects of Humic and Fulvic Acids on Some Physiological Characteristics of Two Ornamental Plants of Granium (Plargonium spp.) and Scindapsus (Scindapsus spp.)

Humic acid and fulvic acid are natural and organic materials, which are derived from various sources such as soil organic matter (humus), soil, peat, oxidized lignite and coal. In order to evaluate the effect of humic substances on physiological characteristics of two ornamental plants of granium (Plargonium spp.) and scindapsus (Scindapsus spp.), an experiment was conducted as 4×4 factorial, based on completely randomized design with three replications, in Research Greenhouse of Ferdowsi University of Mashhad during 2014-2015. The first factor was four levels of humic acid (0, 0.2, 0.5 and 1 g/L) and the second factor was fulvic acid at four levels (0, 0.2, 0.5 and 1 g/L). Results showed that the use of humic acid and fulvic acid caused an improvement in most measured physiological traits in geranium and scindapsus. In granium plant, application of humic acid at low concentration could improve plant growth characteristics. The content of chlorophyll and stomatal conductance in granium increased by humic acid application (0.2 and 0.5 g/L) as fertigation compared to control treatment. Combined application of humic acid and fulvic acid in this plant, also improved soluble sugar content of the plant and reduced the electrolyte leakage as compared to control. In scindapsus, using humic acid at the highest concentration, solely or in combination with fulvic acid, resulted in the improvement of growth traits, so that the combination of humic acid and fulvic acid resulted in increased soluble sugar and SPAD index in this plant. Moreover, chlorophyll content of the plant was increased by the application of humic acid (1 g/L) as fertigation in comparison with the control treatment. These compounds increase plants’ growth by improving their growth conditions. According to the results of this study, application of humic acid and fulvic acid as organic fertilizers is recommended for improving growth in geranium and scindapsus ornamental plants.