Foliar Sprays of Citric Acid and Malic Acid Modify Growth, Flowering, and Root to Shoot Ratio of Gazania (Gazania rigens L.): A Comparative Analysis by ANOVA and Structural Equations Modeling
Foliar application of two levels of citric acid and malic acid (100 or 300？mg？L？1) was investigated on flower stem height, plant height, flower performance and yield indices (fresh yield, dry yield and root to shoot ratio) of Gazania. Distilled water was applied as control treatment. Multivariate analysis revealed that while the experimental treatments had no significant effect on fresh weight and the flower count, the plant dry weight was significantly increased by 300？mg？L？1 malic acid. Citric acid at 100 and 300？mg？L？1 and 300？mg？L？1 malic acid increased the root fresh weight significantly. Both the plant height and peduncle length were significantly increased in all applied levels of citric acid and malic acid. The display time of flowers on the plant increased in all treatments compared to control treatment. The root to shoot ratio was increased significantly in 300？mg？L？1 citric acid compared to all other treatments. These findings confirm earlier reports that citric acid and malic acid as environmentally sound chemicals are effective on various aspects of growth and development of crops. Structural equations modeling is used in parallel to ANOVA to conclude the factor effects and the possible path of effects. 1. Introduction Gazania is a small genus of 16 species, all endemic to southern Africa belonging to the Asteraceae (Compositae) family. It is a member of the tribe Arctoteae, subtribe Gorteriinae, which includes seven other genera: Berkheya, Gorteria, Cuspidia, Didelta, Heterorhachis, Cullumia, and Hirpicium [1]. Besides other flower species, the Gazania rigens L., a member of annual flowers, represents an important decorative material for public greens, gardens, flower stands, and so forth [2]. It is propagated easily and has attractive flowers with a long flowering period, from middle spring to autumn; Gazania is used extensively in urban decorations nowadays. However, Gazania is considered among those landscape groundcovers that are susceptible to water stress [3]. Increasing of ornamental performance is a major concern, especially in harsh urban condition, which demands an increased tolerance to a variety of environmental stresses. Therefore, easy-to-apply practices that can improve the plant performance would be of interest. Endogenous organic acids are the source of both carbon skeleton and energy for cells and are used in the respiratory cycle and other biochemical pathways. Therefore, they can influence the cut flower’s vase life [4]. Malic acid is metabolized in plant mitochondria by reaction of malic enzyme [5]. Malate is a common
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