Nicotiana glauca, a Key Plant for Tomato Growth Enhancement and for the Weed Cynodon dactylon Control

Worldwide, weeds are the costliest category of agricultural pests. They decrease yields and product quality, hence managing them is vital to successful crop cultivation which is the objective of the current study. The present work aims to evaluate the phytotoxicity of the vegetative part and the flowers of Nicotiana glauca on tomato and the weed Cynodon dactylon. Experiments were carried out under field conditions and a number of biochemical and physiological parameters were determined after harvest. The results showed that adding powdered dried flowers to potting soil (in amount of 1%) was the most effective treatment either to inhibit C. dactylon growth or to increase the tomato yield. The stimulations in shoot, root and fresh weight were respectively 35.25%, 328.97%, and 159.04%. It is also remarkable that aqueous extracts of the vegetative part and flowers spray and vegetative part incorporation into soil treatments were effective in stimulating the growth of tomato, but they were less effective in inhibiting the weed growth. In fact, the greatest inhibitions in shoot, rhizomes and fresh weight did not exceed 66.31%, 70.54% and 96.54% after adding powdered dried vegetative part (in amount of 0.6%). The defense strategy developed by lettuce to deal with allelopathic stress could explain the stimulation of tomato growth. Indeed, it increased the production of some metabolites such as polyphenols, flavanols, proanthocyanidins, flavonoids and tannins in addition to proline and carotenoids. An improvement of PAL and TAL activities with a stimulation of the antioxidant activity by increasing DPPH free radicalscavenging activity were also recorded. However, the respiration reduction and the membrane integrity perturbation (demonstrated by an increase in malondialdehyde content and electrolyte leakage) could explain the weed growth inhibition. These findings emphasize that the use of the powdered dried flowers of N. glauca are effective and easily approach to exploit its valuable secondary metabolites either to control C. dactylon or to improve the production of tomato.