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The lulo ( Solanum quitoense Lam.), an underutilized fruit crop originally from the Andes, is still widely unknown in Europe. Because of its delicious taste and high nutrition values it has high potential as greenhouse crop in Central Europe. But production of tropical crops in temperate regions might be limited by seasonal fluctuations in day length. Thus we studied lulo's reproductive development and yield in regard to seasonal photoperiod and supplemental lighting in winter. Therefore, we sow lulo seeds twice a year on 15 February and 20 June 2012 and grew them under natural light conditions so that bloom started in summer (natural long-day) and winter (natural short-day), respectively. Further lulos sown in June were exposed to an artificial long-day photoperiod as of 26 October 2012 (16 h day, ∼150 μmol m −2 s −1 photosynthetic active radiation). We confirmed that in lulo flower initiation and fruit set occurs throughout the year and timing is not significantly different between plants grown under long-day (natural, artificial) and those grown under short-day conditions. However, flower development is affected by photoperiod as first time from bud to fruit set and therefore harvest begin was accelerated at long-days. Second, portion of hermaphroditic flowers increased in andromonoecious lulo in natural, not artificial long-days probably due to higher light intensity. Summer blooming plants bore more fruits (15 fruits per plant) than winter blooming ones (10 fruits). Supplemental lighting in winter only increased fruit number to a comparable amount as in summer but not yield. Surprisingly, blooming and fruiting period was conspicuously longer when flowering started under natural conditions in winter and therefore lasted until spring. So regarding this whole blooming period total yield was even higher when plants were grown during winter without supplemental lighting. In conclusion, reproduction of lulo plants is not restricted to a certain seasonal day length indicating that this crop is suitable for year-round fruit production under greenhouse conditions in Central Europe. [ABSTRACT FROM AUTHOR]

The Indian mock strawberry [ Duchesnea indica (Andrews) Focke] is an invasive plant in several regions of central Europe and Germany. In order to explore its competitive ability, we compared it with the native woodland strawberry ( Fragaria vesca L.) by growing it alone as well as in intra- or inter-specific competition in a pot experiment under greenhouse conditions. Nutrient solution was added several times at two nitrogen (N) levels. One addition involved 15N labelling to determine whether the competition of both plant species depends on their ability to acquire N from soil. Duchesnea had a higher biomass production than Fragaria when grown in nutrient-rich soil, both in competition and as a solitary plant. Under N-poor conditions, root interference could change this superiority due to limited soil space. After 65 days of growth, total plant dry weight, total N content and 15N content in the plant tissues were determined. The results show that the predominance of Duchesnea in biomass production was confirmed at high, but not at low N availability. The assimilate partitioning strategy of Duchesnea differs from that of Fragaria: the former generally had a higher shoot-to-root ratio. The N content in shoots and roots was affected only by N addition but not by competition or species. Duchesnea allocated more N to the leaves, Fragaria to the roots. The amount of 15N taken up was nearly equal for both species. In relation to root biomass, Duchesnea had a higher specific uptake rate at low N addition because of the higher root biomass in Fragaria. The roots of Fragaria and Duchesnea did not affect each other when grown together. We conclude that the invasive potential of Duchesnea is only poorly related to the N uptake rate or to better root competition for N. In N-rich environments, however, Duchesnea is highly competitive because of the preferred investment in shoot biomass. Therefore, environments with increased N deposition, i.e. from anthropogenic sources, could promote the invasive potential of Duchesnea. [ABSTRACT FROM AUTHOR]