First Form, Then Function: 3D Reconstruction of Cucumber Plants (Cucumis sativus L.) Allows Early Detection of Stress Effects through Leaf Dimensions

Detection of morphological stress symptoms through 3D examination of plants might be a cost-efficient way to avoid yield losses and ensure product quality in agricultural and horticultural production. Although the 3D reconstruction of plants was intensively performed, the relationships between morphological and physiological plant responses to salinity stress need to be established. Therefore, cucumber plants were grown in a greenhouse in nutrient solutions under three salinity treatments: 0, 25, and 50 mM NaCl. To detect stress-induced changes in leaf transversal and longitudinal angles and dimensions, photographs were taken from plants for 3D reconstruction through photogrammetry. For assessment of physiological stress responses, invasive leaf measurements, including the determination of leaf osmotic potential, leaf relative water content, and the leaf dry to fresh weight ratio, were performed. The transversal and longitudinal leaf dimensions revealed statistically significant differences between stressed and control plants after 60 °Cd (day 3) for the leaves which appeared before stress imposition. Strong correlations were found between the transversal width and some investigated physiological traits. Morphological changes were shown as indicators of physiological responses of leaves under salinity stress

Compensation of adverse growing media effects on plant growth and morphology by supplemental LED lighting

There is an increasing interest in alternatives to peat in growing media due to environmental constraints. However, plants grown in peat substitutes often show impaired growth compared to plants grown in peat-based media. Hence, it would be interesting to know whether these deficiencies can be compensated by supplementing other growth factors, e.g. light. The present study aims to investigate the interactive nature between growing media and supplemental lighting on plant growth and morphology, and to examine whether supplemental light emitting diode (LED) lighting may compensate adverse growing media effects. Basil (Ocimum basilicum L.) and Chinese cabbage (Brassica rapa subsp. pekinensis) were grown in different growing media consisting of peat, green compost, coconut pulp, wood fibre, perlite and sphagnum moss under blue, red and far-red supplemental LED lighting. We found significant interactions between growing media and supplemental photosynthetically active radiation (PAR) on plant growth, morphology and development. At low light intensities, peat-based and substituted growing media performed similarly, whereas with increasing light intensities the peat-based growing media significantly outperformed their alternatives. The substrate choice determines the required amount of supplemental light to compensate for adverse growing media effects and the amount varies depending on plant species and season. Thereby, it was indicated that red light alleviates adverse growing media effects best. We also found that far-red light is not effective when background PAR is low and becomes more effective under high background PAR. The implications and prospects of the results are discussed

A mechanistic view of the reduction in photosynthetic protein abundance under diurnal light fluctuation

Leaves adapted to diurnal fluctuating light (FL) tend to have reduced photosynthetic parameters in comparison with those grown under constant light but intercepting the same daily photon integral (DPI). This reduction may result from a non-linear relationship between photosynthetic protein synthesis rate (PPSR) and incident photosynthetically active radiation (PAR). Models incorporating the PPSR–PAR relationship have quantitatively predicted the effects of FL reported in the literature. Further simulations suggest that the degree of this reduction varies with the FL pattern, DPI level and parameters describing the PPSR–PAR relationship

Co-Evolution of Sink and Source in the Recent Breeding History of Winter Wheat in Germany

Optimizing the interplay between sinks and sources is of crucial importance for breeding progress in winter wheat. However, the physiological limitations of yield from source (e.g. green canopy duration, GCD) and sink (e.g. grain number) are still unclear. Furthermore, there is little information on how the source traits have been modified during the breeding history of winter wheat. This study analyzed the breeding progress of sink and source components and their relationships to yield components. Field trials were conducted over three years with 220 cultivars representing the German breeding history of the past five decades. In addition, genetic associations of QTL for the traits were assessed with genome-wide association studies. Breeding progress mainly resulted from an increase in grain numbers per spike, a sink component, whose variations were largely explained by the photosynthetic activity around anthesis, a source component. Surprisingly, despite significant breeding progress in GCD and other source components, they showed no direct influence on thousand grain weights, indicating that grain filling was not limited by the source strength. Our results suggest that, 1) the potential longevity of the green canopy is predetermined at the time point that the number of grains is fixed; 2) a co-evolution of source and sink strength during the breeding history contribute to the yield formation of the modern cultivars. For future breeding we suggest to choose parental lines with high grain numbers per spike on the sink side, and high photosynthetic activity around anthesis and canopy duration on the source side, and to place emphasis on these traits throughout selection

High temperature and vapor pressure deficit aggravate architectural effects but ameliorate non-architectural effects of salinity on dry mass production of tomato

Tomato (Solanum lycopersicum L.) is an important vegetable crop and often cultivated in regions exposed to salinity and high temperatures (HT) which change plant architecture, decrease canopy light interception and disturb physiological functions. However, the long-term effects of salinity and HT combination (S+HT) on plant growth are still unclear. A dynamic functional-structural plant model (FSPM) of tomato was parameterized and evaluated for different levels of S+HT combinations. The evaluated model was used to quantify the contributions of morphological changes (architectural effects) and physiological disturbances (non-architectural effects) on the reduction of shoot dry mass under S+HT. The model predicted architectural variables with high accuracy (>85%), which ensured the reliability of the model analyses. HT enhanced architectural effects but reduced non-architectural effects of salinity on dry mass production. The stronger architectural effects of salinity under HT could not be counterbalanced by the smaller non-architectural effects. Therefore, long-term influences of HT on shoot dry mass under salinity were negative at the whole plant level. Our model analysis highlights the importance of plant architecture at canopy level in studying the plant responses to the environments and shows the merits of dynamic FSPMs as heuristic tools.DF

Changes in plant growth, leaf relative water content and physiological traits in response to salt stress in peanut (Arachis hypogaea L.) varieties

Salinity is the main environmental factor accountable for decreasing crop productivity worldwide. The effects of NaCl salinity on plant growth (leaf relative water content (RWC), leaf dry weight (LDW), shoot length (SL), number of leaves (NL), number of branches (NB) and total leaf area (TLA) and physiological characteristics (stomatal conductance (gs), transpiration rate (TR), net photosynthetic (Pn), yield of photosystem II (ΦPsII) and the intercellular CO2 concentration (CO2int) in peanut (Arachis hypogaea L.) varieties (‘Vanda’, ‘P244601’ and ‘Pl184948’, widely used in Cameroon, Tanzania and Ghana, respectively, were investigated under hydroponic condition. Plants were subjected to four levels of NaCl (0, 40, 80 and 120 mM) at early seedling growth stage of plant development. Application of NaCl treatment led to a significant decrease in LDW, SL, NL, TLA, Pn, gs, TR and CO2int concentration of ‘Vanda’ and ‘P244601’ compared to untreated plants while the plant growth inhibition was notably noted at 120 mM NaCl in ‘P1184948’ for LDW, SL and NB. The highest depressive effect was detected in gs of salt-sensitive ‘Vanda’ while the lowest were recorded in gs of salt-tolerant ‘P1184948’ at high salinity level. Enhanced NaCl concentrations led to a significant increase in ΦPSII of ‘P1184948’ compared to ‘Vanda’, ‘P244601’ and untreated plants. Leaf CHL content was significantly increased in moderately-tolerant ‘‘P244601’ and salt-tolerant ‘P1184948’ at 80 mM NaCl compared to salt sensitive ‘Vanda’ and untreated plants. The depressive effect of salt on RWC was recorded at 120 mM NaCl in peanut leaves of all varieties. Under salt stress ‘P1184948’ was observed to have relatively higher tolerance on average of all growth and physiological traits than ‘Vanda’ and P244601’ suggesting that it could be grown in salt-affected soils

SafeSalad - Qualität und Sicherheit in der Produktionskette biologisch produzierter Fertigsalate

Zur Analyse unterschiedlicher Wege einer mikrobiologischen Kontamination mit potenziellem Gesundheitsrisiko wurde die Primärproduktion von verschiedenen Blattsalatarten (Eissalat, Eichblattsalat, Rucola, Mangold) in einem kommerziellen, biologisch produzierenden Betrieb in Norddeutschland in den Jahren 2012, 2013 und 2014 untersucht. Pro Jahr erfolgten jeweils zwei Pflanzungen zu verschiedenen Terminen. Die Pflanzen wurden mit verschiedenen Anbautechniken kultiviert, welche unterschiedliche Gefährdungspotenziale für mögliche Kontaminationen abbilden sollten. Variiert wurden Dünger (Haarmehlpellets, Hühnertrockenkot), Bewässerungssystem (Über-Kopfbewässerung, Tropfbewässerung), Bodenbedeckung (unbedeckter Boden, Mulcheinsatz) sowie genutzte Wasserqualität (Leitungswasser, Brunnenwasser, Teichwasser). Zusätzlich zu den mikrobiologischen Untersuchungen wurden die Auswirkungen der verschiedenen Anbautechniken in Bezug auf das Pflanzenwachstum ana-lysiert. In den Feldversuchen wurden die Wasserqualität als Großteilstück und Düngung, Bewässerung und Bodenbedeckung als Kleinteilstücke in einem Spalt-Spalt-Spaltanlage mit drei Wiederholungen als Blöcke angeordnet. Stichproben von zwei Pflanzen pro Wiederholung und Auswertungstermin wurden zur Charakterisierung der mikrobiologischen Kontamination und des Pflanzenwachstums in einem zweiwöchigen Intervall geerntet und im Anschluss im Labor untersucht. Außerdem wurden Probenahmen und Analysen von Saatgut, Jungpflanzen, Substrat, Düngemittel, Bewässerungswasser, Boden und Blättern durchgeführt. Pflanzenwachstum Die Daten des Pflanzenwachstums zeigten eine signifikante Wirkung der Düngung auf die Frisch- und Trockenmasse. Parzellen die mit Hühnertrockenkot gedüngt wurden zeigten besseres Wachstum und eine höhere Biomasse, während gleichzeitig der Anteil der Trockenmasse bei den Kulturen Eis- und Eichblattsalat reduziert wurde. Für Rucola und Mangold wurden nur wenige signifikante Unterschiede zwischen den Varianten gefunden. Zu Beginn des Wachstums zeigten die Auswertungen einen negativen Mulcheffekt auf die gebildete Frisch- und Trockenmasse. Während der späteren Auswertungen wurden diese Effekte nicht nachgewiesen. Eine Analyse der Qualitätsparameter Nitratgehalt und Strukturkomponenten der Zellwand, die ein Indikator für die Knackigkeit des Produkts sind, zeigte einen Einfluss des Düngers und der Bodenabdeckung. Eissalat, der auf Mulchabdeckung wuchs, zeigte höhere Nitratgehalte und weniger strukturelle Zellwandkohlenhydraten in 2013, wobei der Effekt auf die strukturgebenden Kohlenhydrate 2012 umgekehrt war. Der Einsatz von Hühnertrockenkot zeigte höhere Nitrat-N-Gehalte im Produkt. Insgesamt waren die Unterschiede klein und die Auswirkungen auf die Produktqualität zu vernachlässigen. Mikrobiologie/Modellierung Die risikofreudigeren Anbaumethoden im Freilandversuch (Hühnertrockenkot, Überkopfbewässerung mit Teichwasser, keine Mulchabdeckung) resultierten in keiner messbaren Änderung der mikrobiellen Besiedelung. Dies sollte jedoch nicht die Gefahr, welche von Input mit schlechter mikrobiologischer Qualität ausgeht, verharmlosen. Manche Krankheitserreger wie z.B. humanpathogene E. coli haben eine niedrige Infektionsdosis von unter 100 Bakterien (Rheinbaben, 2011). Folglich können auch schon geringe Mengen an Bakterien, welche unter dem Detektionslimit der hier angewandten Analysemethoden liegen und somit nicht er-fasst würden, zu schweren Krankheitsausbrüchen führen. In Gewächshausversuchen konnte gezeigt werden, dass E. coli O157:H7 gut auf Blättern überlebt, und dass die Kolonisierung unabhängig von der N-Quelle vorkommt, wenn E. coli O157:H7 auf anderem Wege als durch Dünger eingebracht wird. Von Bedeutung ist weiterhin die Möglichkeit einer Internalisierung von E. coli O157:H7. Dabei ist die Unversehrtheit der Salatblätter entscheidend, da festgestellt werden konnte, dass eine Schädigung die Invasion von E. coli O157:H7 begünstigen und somit zu einem erhöhten Risiko beitragen kann. Zur Verminderung des Kontaminationsrisikos müssen schon während der Produktion im Freiland oder Gewächshaus Maßnahmen (z.B. durch Anwendung des HACCP-Konzeptes) ergriffen werden. In keinem der angebauten Freilandsätze traten allerdings zum Erntetermin Kontaminationen oberhalb der Warnwerte der Dt. Gesellschaft für Hygiene (DGHM, 2011) auf. Eine Modellierung der Zusammenhänge zwischen Kontaminationsquelle, -zeitpunkt, Befallsdynamik und Umweltdaten war leider nicht möglich, da es im Versuchszeitraum nur zu geringer bzw. in einigen Sätzen zu keiner Kontamination kam. Dessen ungeachtet wurde zumindest die Grundstruktur eines Modells entwickelt

Changes in plant growth, leaf relative water content and physiological traits in response to salt stress in peanut (Arachis hypogaea L.) varieties

Salinity is the main environmental factor accountable for decreasing crop productivity worldwide. The effects of NaCl salinity on plant growth (leaf relative water content (RWC), leaf dry weight (LDW), shoot length (SL), number of leaves (NL), number of branches (NB) and total leaf area (TLA) and physiological characteristics (stomatal conductance (gs), transpiration rate (TR), net photosynthetic (Pn), yield of photosystem II (OPsII) and the intercellular CO2 concentration (CO2int) in peanut (Arachis hypogaea L.) varieties (‘Vanda', ‘P244601' and ‘Pl184948', widely used in Cameroon, Tanzania and Ghana, respectively, were investigated under hydroponic condition. Plants were subjected to four levels of NaCl (0, 40, 80 and 120 mM) at early seedling growth stage of plant development. Application of NaCl treatment led to a significant decrease in LDW, SL, NL, TLA, Pn, gs, TR and CO2int concentration of ‘Vanda' and ‘P244601' compared to untreated plants while the plant growth inhibition was notably noted at 120 mM NaCl in ‘P1184948' for LDW, SL and NB. The highest depressive effect was detected in gs of salt-sensitive ‘Vanda' while the lowest were recorded in gs of salt-tolerant ‘P1184948' at high salinity level. Enhanced NaCl concentrations led to a significant increase in OPSII of ‘P1184948' compared to ‘Vanda', ‘P244601' and untreated plants. Leaf CHL content was significantly increased in moderately-tolerant ‘‘P244601' and salt-tolerant ‘P1184948' at 80 mM NaCl compared to salt sensitive ‘Vanda' and untreated plants. The depressive effect of salt on RWC was recorded at 120 mM NaCl in peanut leaves of all varieties. Under salt stress ‘P1184948‘ was observed to have relatively higher tolerance on average of all growth and physiological traits than ‘Vanda’ and P244601' suggesting that it could be grown in salt-affected soils

How does structure matter? Comparison of canopy photosynthesis using one- And three-dimensional light models: A case study using greenhouse cucumber canopies

One-dimensional light models using the Beer-Lambert equation (BL) with the light extinction coefficient k are simple and robust tools for estimating light interception of homogeneous canopies. Functional-structural plant models (FSPMs) are powerful to capture light-plant interactions in heterogeneous canopies, but they are also more complex due to explicit descriptions of three-dimensional plant architecture and light models. For choosing an appropriate modelling approach, the trade-offs between simplicity and accuracy need to be considered when canopies with spatial heterogeneity are concerned. We compared two light modelling approaches, one following BL and another using ray tracing (RT), based on a framework of a dynamic FSPM of greenhouse cucumber. Resolutions of hourly step (HS) and daily step (DS) were applied to simulate light interception, leaf-level photosynthetic acclimation and plant-level dry matter production over growth periods of 2-5 weeks. Results showed that BL-HS was comparable to RT-HS in predicting shoot dry matter and photosynthetic parameters. The k used in the BL approach was simulated using an empirical relationship between k and leaf area index established with the assistance of RT, which showed variation up to 0.2 in k depending on canopy geometry under the same plant density. When a constant k value was used instead, a difference of 0.2 in k resulted in up to 27 % loss in accuracy for shoot dry matter. These results suggested that, with the assistance of RT in k estimation, the simple approach BL-HS provided efficient estimation for long-term processes