Evaluation of Gibberellic Acid and Humic Acid on Morpho-physiological indices and Vase life of Cut Flower Daffodil (Narcissus pseudonarcissus)

Narcissus is one of the most important ornamental bulbous plant in the temperate regions which it can be used as cut flower or flowering potted-plant (14). Moreover, this flower is planted in high volume for the beautification of scenery and environment in parks and gardens. One of the limiting factors in the post-harvest vase life and selling of narcissus is its short post-harvest life and quick wilting of its petals. Fresh cut flowers of narcissus have a very short vase life of around 4 to 8 days (6). Flower senescence after harvest is a major limiting factor in cut flower production. Any factor that can cause delay or disable the destructive or physiological processes in cut flowers can improve post-harvest life (12). The production of cut flowers with suitable quality and long vase life is one of the favorite economical activities in the industry (2). Previous studies tried to look for procedures to improve the quality and quantity of cut flowers and ornamental plant production, and amongst them, plant growth regulators have a special importance specifically in gibberellic acid effects (10). Humic acid is a natural organic polymer which can improve quality and durability of ornamental plants, directly such as hormone-like substances of gibberellic acid, auxin, and cytokinin and indirectly by increasing absorption and translocation of nutrients in the plant (20). The general purposes of the current study were to improve vase life of narcissus (German cultivar) and to determine the best concentration of gibberellic acid and humic acid.
The current study aimed to investigate the effects of gibberellic acid and humic acid on various indicators of growth and vase life of narcissus flower. It was conducted on the basis of the factorial experiment with randomized complete block design which consisted of with two experimental factors, 12 treatments, and replicated three times. In each replication there were five pots and for each pot one bulb was cultivated and the total number of cultivated pots were 180. Experimental factors were gibberellic acid in four levels (150, 300, 450 ppm and control) and humic acid in three levels (250, 500 ppm and control).
Results from analysis of variance table showed that the effect of gibberellic acid on the height of floral stem, the total soluble solids and the cell membrance stability index was significant in comparison with control (Table 2). Gibberellic acid and humic acid treatments independently had significant differences on the relative fresh weight and vase life of narcissus cut flowers. Also diameter of floral stem and calcium content were increased by humic acid treatment. Interaction between treatments of gibberellic acid 300 ppm and humic acid 500 ppm resulted in the highest length of leaf.
This research concludes that the best treatments for improvement of vase life and the researched properties of narcissus were the 300 ppm gibberellic acid and 500 ppm humic acid concentrations.