Influence of soil moisture levels on the growth and reproductive behaviour of Avena fatua and Avena ludoviciana.

Adaptation of weeds to water stress could result in the broader distribution, and make weed control task increasingly difficult. Therefore, a clear understanding of the biology of weeds under water stress could assist in the development of sustainable weed management strategies. Avena fatua (wild oat) and A. ludoviciana (sterile oat) are problematic weeds in Australian winter crops. The objectives of this study were to determine the growth and reproductive behaviour of A. fatua and A. ludoviciana at different soil moisture levels [20, 40, 60, 80, and 100% water holding capacity (WHC)]. Results revealed that A. fatua did not survive and failed to produce seeds at 20 and 40% WHC. However, A. ludoviciana survived at 40% WHC and produced 54 seeds plant-1. A. fatua produced a higher number of seeds per plant than A. ludoviciana at 80 (474 vs 406 seeds plant-1) and 100% WHC (480 vs 417 seeds plant-1). Seed production for both species remained similar at 80 and 100% WHC; however, higher than 60% WHC. Seed production of A. fatua and A. ludoviciana was 235 and 282 seeds plant-1, respectively, at 60% WHC. The 60% WHC reduced seed production of A. fatua and A. ludoviciana by 51 and 32% respectively, compared to 100% WHC. The plant height, leaf weight, stem weight, and root weight per plant of A. fatua at 60% WHC reduced by 45, 27, 32, and 59%, respectively, as compared with 100% WHC. Similarly, the plant height, leaf weight, stem weight, and root weight per plant of A. ludoviciana at 60% WHC reduced by 45, 35, 47 and 76%, respectively, as compared with 100% WHC. Results indicate that A. ludoviciana can survive and produce seeds at 40% of WHC, indicating the adaptation of the species to dryland conditions. The results also suggest that A. ludoviciana is likely to be robust under water stress conditions, potentially reducing crop yield. The ability of A. fatua and A. ludoviciana to produce seeds under water-stressed conditions (60% WHC) necessitates integrated weed management strategies that suppress these weeds whilst taking into account the efficient utilization of stored moisture for winter crops.

Quantitative high-performance liquid chromatography analyses of flavonoids in Australian Eucalyptus honeys.

Flavonoids of nine Australian monofloral Eucalyptus honeys have been analyzed and related to their botanical origins. The mean content of total flavonoids varied from 1.90 mg/100 g of honey for stringybark (E. globoidia) honey to 8.15 mg/100 g of honey for narrow-leaved ironbark (E. crebra) honey, suggesting that species-specific differences occur quantitatively among these Eucalyptus honeys. All of the honey samples analyzed in this study have a common flavonoid profile comprising tricetin (5,7,3',4',5'-pentahydroxyflavone), quercetin (3,5,7,3',4'-pentahydroxyflavone), and luteolin (5,7,3',4'-tetrahydroxyflavone), which, together with myricetin (3,5,7,3',4',5'-hexahydroxyflavone) and kaempferol (3,5,7,4'-tetrahydroxyflavone), were previously suggested as floral markers for European Eucalyptus honeys. Thus, flavonoid analysis could be used as an objective method for the authentication of the botanical origin of Eucalyptus honeys. Moreover, species-specific differences can also be found in the composition of honey flavonoid profiles. Among these honeys, bloodwood (E. intermedia) honey contains myricetin and tricetin as the main flavonoid compounds, whereas there is no myricetin detected in yapunyah (E. ochrophloia), narrow-leaved ironbark (E. crebra), and black box (E. largiflorens) honeys. Instead, these types of Eucalyptus honeys may contain tricetin, quercetin, and/or luteolin as their main flavonoid compounds. Compared to honeys from other geographical origins, the absence or minor presence of propolis-derived flavonoids such as pinobanksin, pinocembrin, and chrysin in Australian honeys is significant. In conclusion, these results demonstrate that a common flavonoid profile exists for all of the Eucalyptus honeys, regardless of their geographical origins; the individual species-specific floral types of Eucalyptus honey so common in Australia could be possibly differentiated by their flavonoid profile differences, either qualitatively or quantitatively or both.