Changes of stem water potential of grapevine cv. Frankovka (Vitis vinifera L.) in different crop load models Section 8 . Viticulture and Enology Changes of stem water potential of grapevine cv. Frankovka (Vitis vinifera L.) in different crop load models

Abstract Water status of grapevine, observed as stem water potential (Ψ stem ) have been investigated in field conditions on plants that were in different yields treatments. Plant water status was examined through the measurement of stem water potential (Ψ stem ) at the interval of 7 -10 days, from June to September. The research goal has been to monitor water status changes in the field conditions that might occur depending on the pruning strength. Numerous factors, from climatic to the various number of shoots and bunches, depending on the load variant, simultaneously influenced and possibly caused certain changes. Differences in yield were affected by leaving of 8 (v1), 16 (v2) and 24 (v3) winter buds per vine. Tree-year study showed that minimum values of stem water potential were recorded in the variant with 8 buds per vine, when the average yield was 2.03 kg per vine. The leaf area/crop weight was averagely 1.11 m 2 /kg in this variant. In case of the mentioned bud load, Ψ stem values ranged to -0.93 Mpa (July 15, 2004) and -0.65 MPa (July 27, 2006). These values indicated on unfavorable water status in v 1 than other two variants, in which the values are not decreased below -0.81 Mpa (22.7.2004) and -0.65Mpa (27.7.2006). The average yield in these variants were v 2 =3,4kg per vine and v 3 =4,8kg during the examined period. When statisticaly relevant differences were recorded among Ψ stem values of v 1 and the other two bud load variants, their values considerably approached critical values which indicating the commencement of stressful conditions due to water deficit

Autochthonous and international grape varieties grown in Serbia - Phenolic and elemental composition

The phenolic and elemental profiles of Serbian autochthonous grape varieties ‘Smederevka’ and ‘Plovdina’ were studied and compared with some international varieties. Total phenolic content and radical scavenging activity were highest in seeds of ‘Plovdina’, and in ‘Smederevka’ skins, which also had the highest contents of ferulic, chlorogenic and caffeic acids (16.0, 1.44 and 0.98 mg/kg, respectively). Protocatechuic acid was quantified only in the seeds of these varieties. Untypically for Vitis vinifera L. species, the presence of malvidin 3,5-O-dihexoside was found in the skins of ‘Vranac’ and ‘Muscat Hamburg’. In ‘Plovdina’ skins among the anthocyanins, hexosides of peonidin and delphinidin were prevalent. ‘Plovdina’ grapes had lower quantities of Al, Ni and Na in comparison to the other varieties intended for white wine production. Significant correlations among the most abundant elements, such as K, P, Ca, Mg, S, Fe, Cu, and Zn, pointed to potential positive interactions. For elements that have toxicological reference values, the health risk assessment was calculated for adults and children, and suggested that all samples were safe for human consumption