Germination and Seedling Growth of a Set of Rapeseed (Brassica napus) Varieties under Drought Stress Conditions

Drought stress is one of the major abiotic factors affecting seed germination and plant growth especially in arid and semi-arid regions. In this study, we investigated the effects of drought stress on seed germination and seedling growth of five varieties of rapeseed. Seven drought stress levels of zero (control), -3, -5, -7, -9, -11 and -13 bars were performed using polyethylene glycol-6000 (PEG-6000). A completely randomized design with three replications was used for this experiment. Germination percentage (GP), germination rate (GR), mean germination time (MGT), root length (RL) and shoot length (SL) were measured to evaluate the varieties response to PEG-induced drought stress. Drought stress, variety and the interaction drought × variety had a significant effect on all studied parameters. GP and GR decreased with the increase in stress level, while MGT increased. There were no seeds germinated for all varieties at -11 bars and -13 bars. Shoot length decreased with increasing drought stress but different varieties show different performance under stress environment. Root length decreased with increasing level of severe drought stress. However, the presence of moderate drought stress could even improve the root growth of the investigated varieties. The varieties ‘INRA-CZH2' and ‘INRA-CZH3' exhibited the highest germination percentage and the best early seedling growth. Thus, they could be recommended for environments with early cropping cycle drought

Attributs de qualité, propriétés chimiques et composés bioactifs du jus de grenade (Punica granatum L.) transformé à partir d'arilles après congélation

Pomegranate juice quality depends essentially on its chemical and nutritional components stability. The valuable nutritional components may be reduced during its processing or storage. This study examined the effect of pomegranate arils’ frozen storage on juice quality, in terms of physicochemical properties and bioactive compounds stability. The physicochemical criteria (pH, TSS, TA, color attributes) and biochemical criteria (Total Phenolic content, Total anthocyanin content and antioxidant activity) were assessed on pomegranate juice extracted from frozen arils stored at (-18°C) for 6 months. Two cultivars ‘Sefri’ and ‘Wonderful’ were subject to this study. Results showed that the pH, TSS, and TA were generally stable in frozen arils juice. However, arils freezing had a significant effect on pomegranate juice color parameters. In fact, a significant decrease of a* values were revealed in juice samples for both cultivars. Therefore, the color intensity (chroma) has decreased significantly and total color differences (ΔE∗ab) also showed a significant difference (p < 0.05) between fresh juice and frozen arils juice. Arils freezing conditions (−18 °C) for 6 months didn’t affect pomegranate juice physiochemical criteria. However, bioactive compounds of pomegranate juice were reduced significantly. In fact, total phenolic content decreased by about 27% and 31% for ‘Sefri’ and ‘Wonderful’ cultivars, respectively. Total anthocyanins content decreased by 20% and 30% for ‘Sefri’ and ‘Wonderful’ cultivars, respectively. Antioxidant activity, measured based on the juice’s radical scavenging properties using the 2,2-diphenyl-1-picrylhydrazyl method, decreased by about 50% for ‘Sefri’ cultivar and 60% for ‘Wonderful’ cultivar.La qualité du jus de grenade dépend essentiellement de la stabilité de ses propriétés chimiques et nutritionnelles. L'objectif de cette étude est d'examiner l'effet de la congélation des arilles de grenade sur la qualité du jus, en termes de propriétés physicochimiques et de stabilité des composés bioactifs. Les critères physicochimiques (pH, TSS, TA, paramètres de la couleur) et biochimiques (teneur en polyphénols totaux, teneur en anthocyanes totaux et l’activité antioxydante) ont été évalués sur le jus de grenade extrait d'arilles congelées stockées à (-18°C) pendant 6 mois. Deux cultivars 'Sefri' et 'Wonderful' ont fait l'objet de cette étude. Les résultats ont montré que le pH, le TSS et le TA étaient généralement stables dans le jus d'arilles congelé. Cependant, la congélation des arilles a eu un effet significatif sur les paramètres de couleur du jus de grenade. En fait, une diminution significative des valeurs a* a été révélée dans les échantillons de jus pour les deux cultivars. Par conséquent, l'intensité de la couleur (chroma) a diminué de manière significative et les différences totales de couleur (ΔE∗ab) ont également montré une différence significative (p < 0,05) entre le jus frais et celui d'arilles congelées. La teneur des polyphénols totaux du jus d'arilles congelées a diminué d'environ 27% pour le cultivar 'Sefri' et de 31% pour le cultivar 'Wonderful'. De plus, la teneur totale en anthocyanes a diminué de 20% pour le cultivar 'Sefri' et de 30% pour le cultivar 'Wonderful'. L'activité antioxydante, mesurée sur la base des propriétés de piégeage des radicaux du jus par la méthode du 2,2-diphényl-1-picrylhydrazyl, a diminué d'environ 50% pour le cultivar 'Sefri' et de 60% pour le cultivar 'Wonderful'. Le stockage des arilles dans des conditions de congélation (-18 °C) pendant 6 mois n'a pas affecté les critères physico-chimiques du jus de grenade, cependant, les composés bioactifs du jus de grenade ont été réduits de manière significative