Effect of Humic Acid on Vegetative and Reproductive Growth of Squash (Cucurbita pepo L.) under Saline Stress Conditions

Abstract

In order to investigate the effect of Humic acid (HA) on growth and development of squash plants (Cucurbita pepo L.) cv. Alexandria F1 under salinity conditions, three concentrations of HA: 0, 200 and 400 ppm and four concentrations of salinity (NaCl): 500 (tap water), 1000, 2000 and 3000 ppm were used with irrigation. The number of leaves (NL), length (LP) and thickness (TP) of petioles, leaf area (LA), fresh weight (FWP), dry weight (DWP) and percentage of dry weight of plants (PDW) were measured at the end of the vegetative stage. The sex ratio of female flowers (SR), number of fruits (FN), fresh (FFW) and dry (FDW) weight of fruits were measured during the reproductive stage. The results indicate that treatment with HA led to a reduction in the severity of salinity effect in some of the vegetative parameters under salinity condition compared to the control treatment. In contrast, the reproductive parameters were decreased as the salinity increased without an apparent effect of applying the used HA concentrations. The results of this experiment suggest that the ability of HA treatment to ameliorate the vegetative growth process was not sufficiently reflected in the reproductive growth under salinity condition. Therefore, the lack of amelioration may be attributed to the inefficiency of the HA concentrations used in this experiment.

Keywords: Cucurbita pepo L.; Humic acid; NaCl; Salinity