Impact of foliar potassium fertilization on biochemical composition and antioxidant activity of fig (Ficus carica L.)

The metabolic processes involved in fig production are influenced by macro- and micronutrients supply to the trees during the growing season. Potassium is an essential plant nutrient that influences growth and fruit quality. In this study, the effect of foliar potassium sulphate (K2SO4) application on biochemical composition and antioxidant activity of fig was assessed in cv. Bouhouli, a commonly cultivated cultivar in Djebba (Northwest of Tunisia). Foliar potassium sulphate supply at 2% on Bouhouli trees were applied twice during the fruit growth. Results exhibited that potassium fertilization induces a significant change in total phenolic, flavonoid contents and radical scavenging activity in total fruit and achenes compared to the control. A strong correlation was observed between antioxidant activity and different phenolic compounds. The total fruit and achenes methanol extracts possess, respectively, the highest values of polyphenol by 29.3 and 25.1 mg GAE/g DW compared to the control. Similarly, the flavonoids content was increased in methanol extracts, respectively, by 36 and 48%. HPLC analyses revealed the influence of potassium on concentrations of phenolic compounds in fig sprayed with K2SO4. Among the polyphenols, the chlorogenic acid, cyanidin 3-rutinoside and cyanidin 3,5-diglucoside contents increased from 0.87 to 1.70 mg/g DW under potassium spray, whereas those compounds were not detected in fig achenes. The present study provides clear evidence that potassium sulphate can be used to manipulate total phenolic concentrations in fig with strong antioxidant potential that could be benefits to human health. Thus, potassium sulphate application at 2% could improve nutritional and qualitative attributes of fig

Allelopathic potential and phenolic allelochemicals discrepancies in Ficus carica L. cultivars

The phytotoxic effect of some tree species could act as an ecological filter through chemical production that influences plant growth of other species. Despite this widespread interest, few studies have investigated the allelopathic effect of some Moraceae species, while this mechanism has not been studied in Ficus carica. To address this research, we attempted to identify the allelopathic mechanisms of thirteen local preserved fig cultivars on the germination and seedling growth of common weeds and standard target species. The results stated that all fig extracts displayed significant phytotoxic impact, and the degree of inhibition was appeared to be dependent on the cultivars and target species. In general, leaf extracts were more toxic and significantly influenced the seedling elongations, as compared to twig extracts. It was clearly marked that the germination and growth of weed species were totally affected by leaf aqueous and methanol extracts of cultivars Kahli and Bouhouli, respectively, at 40 g/L and 6 g/L. The phytochemical analysis through high performance liquid chromatography detected similar profile among cultivars but with a significant disparity in phenolic composition. Among the identified compounds, rutin is the major flavonoid compound recorded in cv. Zidi and was highly accumulated in leaf rather than in twig. It was obvious that the different fig cultivars or even their tissues can be characterized and clustered in three groups based on their allelopathic potential and phenolic compounds