We have cloned and characterized VvNHX1, a gene encoding a vacuolar cation/H(+) antiporter from Vitis vinifera cv. Cabernet Sauvignon. VvNHX1 belongs to the vacuolar NHX protein family and showed high similarity to other known vacuolar antiporters. The expression of VvNHX1 partially complements the salt- and hygromycin-sensitive phenotypes of an ena1-4 nhx1 yeast strain. Immunoblots of vacuoles of yeast expressing a VvNHX1, together with the expression of a VvNHX1-GFP (green fluorescent protein) chimera demonstrated that VvNHX1 localized to the vacuoles. VvNHX1 displayed low affinity K(+)/H(+) and Na(+)/H(+) exchange activities (12.8 and 40.2 mM, respectively). The high levels of expression of VvNHX1 during the véraison and post-véraison stages would indicate that the increase in vacuolar K(+) accumulation, mediated by VvNHX1, is needed for vacuolar expansion. This process, together with the rapid accumulation of reducing sugars, would drive water uptake to the berry and the concomitant berry size increase, typical of the post-véraison stage of growth.

The chemical composition of the essential oils of Melaleuca armillaris Sm., Melaleuca styphelioides Sm. and Melaleuca acuminata F. Muell., collected in Tunisia, was studied by means of GC and GC-MS analysis. In all, 46 compounds were identified, 38 for M. armillaris, 20 for M. acuminata and eight for M. styphelioides, respectively. The presence of a sesquiterpenic fraction (52.2%) characterized the oil from M. armillaris; M. sthypheliodes oil was rich in methyl eugenol, a phenolic compound (91.1%), while M. acuminata oil is mainly constituted by oxygenated monoterpenoids (95.6%). The essential oils were evaluated for their in vitro potentially phytotoxic activity against germination and initial radicle growth of Raphanus sativus L., Lepidium sativum L., Sinapis arvensis L., Triticum durum L. and Phalaris canariensis L. seeds. The radicle elongation of five seeds was inhibited at the highest doses tested, while germination of all seeds was not affected. Moreover, the essential oils showed low antimicrobial activity against eight selected microorganisms.

The chemical composition of essential oils isolated by hydrodistillation from the aerial parts of Tunisian Pinus pinea Linn. was analyzed by GC and GC/MS. Sixty-six compounds were identified, representing 98.5% of total oil, which was found to be rich in monoterpene hydrocarbons (73.1%) particularly limonene (54.1%), a-pinene (7.7%), and b-pinene (3.4%). The yield and the physico-chemical properties were determined. Results of the antifungal activity study by in vitro contact assay showed that P. pinea oil significantly inhibited the growth of ten plant pathogenic fungi. Moreover, herbicidal properties of the oil, tested on Sinapis arvensis L., Lolium rigidum Gaud., and Raphanus raphanistrum L., indicated that the oil completely inhibited the seed germination at a high concentration, while at low doses the oil acted by decreasing and delaying the germination and inhibiting the seedling growth of all tested weeds unlike the commercial herbicide. Our results showed that P. pinea essential oil could be valorized as bioproduct for biocontrol of weeds and fungal plant diseases.

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