Leibniz Institute of Vegetable and Ornamental Crops Grossbeeren/Erfurt e.V., Theodor-Echtermeyer-Weg 1, 14979 Grossbeeren, Germany.
Plant Physiol Biochem. 2013 Nov;72:154-60. doi: 10.1016/j.plaphy.2013.05.006. Epub 2013 May 18.
Applying transparent daytime screens in greenhouses in cool seasons reduces the amount of energy needed for heating, but also the solar radiation available for crops. This can reduce yield and product quality of leafy vegetables because of constrained photosynthesis and altered biosynthesis. To study this, we cultivated five-week old red leaf lettuce (Lactuca sativa L.) for four weeks in growth chambers under a photosynthetic photon flux density (PPFD) of 225 and 410 μmol m(-2) s(-1), respectively. Some plants were exchanged between radiation intensities after two weeks. We investigated the concentration of five flavonoid glycosides, three caffeic acid derivatives, reducing sugars as well as plant growth. Remarkably, no significant influence of radiation intensity on the concentration of phenolic acids or anthocyanin glycosides was observed. In contrast, quercetin and luteolin glycoside concentration was between 14 and 34% lower in plants growing under lower compared to higher PPFD. Already after two weeks of cultivation, plants grown under lower PPFD contained less quercetin and luteolin glycosides but they completely compensated if subsequently transferred to higher PPFD until harvest. Hence, marketable lettuce heads which experienced temporary shading followed by an unshaded phase did not contain lower concentrations of flavonoid glycosides or phenolic acids. Also, there was no reduction of head mass in this variant. Our results suggest that saving energy in early growth stages is feasible without losses in yield or health promoting phenolic substances. In addition, there was a close correlation between the concentration of reducing sugars and some flavonoid glycosides, indicating a close metabolic connection between their biosynthesis and the availability of carbohydrates.
在凉爽季节的温室中使用透明白天遮阳幕可以减少加热所需的能源，但也会减少作物可用的太阳辐射。这可能会降低叶菜类蔬菜的产量和产品质量，因为光合作用受到限制和生物合成发生改变。为了研究这一点，我们在光合光子通量密度（PPFD）分别为 225 和 410 μmol m(-2) s(-1)的生长室中培养了五周大的红色生菜（Lactuca sativa L.）四周。两周后，一些植物在辐射强度之间进行了交换。我们研究了五种类黄酮糖苷、三种咖啡酸衍生物、还原糖以及植物生长的浓度。值得注意的是，辐射强度对酚酸或花青素糖苷的浓度没有显著影响。相比之下，在较低的 PPFD 下生长的植物中，槲皮素和木樨草素糖苷的浓度比在较高的 PPFD 下低 14%至 34%。甚至在培养两周后，在较低 PPFD 下生长的植物中，槲皮素和木樨草素糖苷的含量就较低，但如果随后转移到较高的 PPFD 下，它们就会完全补偿，直到收获。因此，经历过临时遮荫然后恢复无遮荫阶段的可销售生菜头不含较低浓度的类黄酮糖苷或酚酸。在这种变化中，头质量也没有减少。我们的结果表明，在早期生长阶段节约能源是可行的，不会导致产量或健康促进酚类物质的损失。此外，还原糖的浓度与一些类黄酮糖苷之间存在密切的相关性，表明它们的生物合成与碳水化合物的可用性之间存在密切的代谢联系。
