Ascophyllum nodosum extract improves leaf thermoregulation by reducing stomatal sensitivity to VPD in Vitis vinifera L

AbstractClimate change scenarios and the need of sustainable tools to reduce global warming impact on agriculture have led to the formulation of a large number of natural products or biostimulants that should increase plant resilience to abiotic stress. Ascophyllum nodosum (AN) extract is one of the most studied biostimulants to increase tolerance to drought stress, but the physiological mechanism underlying its action is still poorly understood. The aim of the present work was to determine AN extract impact on grapevine gas exchange under well-watered and water stress conditions and to examine its mode of action under stress (light and temperature). AN caused a slight increase in stomatal conductance that resulted in an increase of water plant conductivity to atmosphere. Increased transpiration induced by AN improved leaf thermoregulation, facilitating vine recovery after a stress period. AN increased transpiration through a reduction of stomatal sensitivity to VPD. AN action on stomata regulation indicated that this biostimulant could be a new potential tool to limit leaf damage during events of extreme temperature, even when they are not combined with water stress conditions

Changes in Within-Shoot Carbon Partitioning in Pinot Noir Grapevines Subjected to Early Basal Leaf Removal

Early leaf removal significantly alters the source-sink balance within grapevine shoots, leading to a reduction in fruit set. However, no research has previously examined the conditions controlling this process in terms of carbon allocation among major sink organs following defoliation. In this study, the impact of defoliation at bloom on the distribution dynamics of leaf assimilates among clusters and growing shoot apices was investigated on Vitis vinifera, cv. Pinot noir, grown in Michigan, a cool climate viticultural region. Three levels of defoliation: no leaves removed (LR-0); six leaves removed from six basal nodes (LR-6); and ten leaves removed from ten basal nodes (LR-10), were imposed at full bloom. A 13C pulsing was performed 1 week after the treatment application to the defoliated shoots. Single leaf gas exchange (Pn), diurnal changes of the leaf net CO2 assimilation rate, carbon distribution, fruit-set, yield, and fruit composition were measured. Higher Pn was recorded in diurnal measurements of gas exchange in leaf removal (LR) treatments compared to LR-0. The shoot apex of LR-10 experienced the highest 13C allocation (%) after 3 and 7 days following the carbon pulsing. LR-10 had lower percentage of 13C allocated to clusters, which decreased fruit set by 60%, compared to the control, and enhanced the concentration of phenolic compounds in fruit. Alteration of carbon portioning among shoot sink organs indicated that an increasing severity of leaf removal significantly reduced fruit set, and was linearly correlated to shoot apex sink strength, which occurred at the expense of the cluster

Double cropping in Vitis vinifera L. cv. Pinot Noir: agronomical and physiological validation

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Effects of a new arbuscular mycorrhizal fungus (Glomus iranicum) on grapevine development

During the spring of 2016, one-year-old own-rooted and 3-year-old grafted vines of cv. Sangiovese were treated with MycoUp, a formulation based on a recently identified mycorrhizal fungus, Glomus iranicum var. tenuihypharum sp. nova. The results are showing an impact on the development of the root system of the two different vine groups. The treated root systems were more expanded and able to explore a higher volume of soil. We observed a significant increase in total root volume and the volume of the soil explored by the entire root system, suggesting a more efficient use of water and nutrients, phosphorus in particular, with the potential of better overcoming periods of water stress

Kaolin treatments on Pinot noir grapevines for the control of heat stress damages

The aim of the study was to verify if vineyard kaolin application during the 2017 hot summer could reduce the negative effects of high temperatures and heat stress on canopy physiological processes, yield and fruit quality. The kaolin was applied once at the beginning of August, at 3% concentration, in a Pinot Noir vineyard. The application was performed only to the west side of the rows, where the vines were more subjected to heat stress. The 2017 summer was very hot, with maximum air temperature higher than 35 °C for several consecutive days in June, July and August and with heat waves that reached 42.3 °C in August. The kaolin coating works by significantly reducing leaf temperatures in comparison to untreated vines, with an average of about − 4 °C and up to −6 °C. Moreover, it maintains high the photosynthetic activity preventing irreversible photoinhibition phenomena, whereas untreated vines exhibit a marked physiological damage with chlorotic and necrotic leaves, dehydrated berries and sunburn damages. At harvest, 30-35% of the untreated vines were affected by severe water stress symptoms and produced unmarketable fruits. In comparison to the untreated vines, those sprayed with kaolin showed a higher yield (+27%), higher anthocyanins (+35%) and higher concentration of organic acids (+11%

Carbon partitioning between shoot organs following early leaf removal

In grapevines, basal leaf removal at bloom often induces a reduction of fruit set. The effect is related to a reduction in carbon availability for different plant organs competing for photosynthates. To understand and quantify carbon allocation among major sink organs following the early basal leaf removal, the effect of early basal defoliation was studied in Pinot noir grapevines. The experiment was performed in Michigan, a cool climate viticultural region, and three levels of defoliation were imposed at full bloom: (1) no leaves removed (DF-0); (2) six leaves removed from six basal nodes (DF-6); and (3) ten leaves removed from ten basal nodes (DF-10). A week after the defoliation treatment, 13C pulsing was executed to the defoliated shoots. Photosynthesis (Pn), carbon distribution, fruit set, vine performance and basic fruit composition were measured. LR treatments induced higher Pn when compared to LR-0. The highest 13C allocation (%) was recorded in the shoot apex of the LR-10 treatment and LR-10 had the lowest percentage of 13C transported to the cluster, with a reduced fruit set of about 60% when compared to LR-0. The severity of leaf removal reduced significantly fruit set and increased shoot apex sink strength at the expense of the cluster

Carbon partitioning between shoot organs following early leaf removal

In grapevines, basal leaf removal at bloom often induces a reduction of fruit set. The effect is related to a reduction in carbon availability for different plant organs competing for photosynthates. To understand and quantify carbon allocation among major sink organs following the early basal leaf removal, the effect of early basal defoliation was studied in Pinot noir grapevines. The experiment was performed in Michigan, a cool climate viticultural region, and three levels of defoliation were imposed at full bloom: (1) no leaves removed (DF-0); (2) six leaves removed from six basal nodes (DF-6); and (3) ten leaves removed from ten basal nodes (DF-10). A week after the defoliation treatment, 13C pulsing was executed to the defoliated shoots. Photosynthesis (Pn), carbon distribution, fruit set, vine performance and basic fruit composition were measured. LR treatments induced higher Pn when compared to LR-0. The highest 13C allocation (%) was recorded in the shoot apex of the LR-10 treatment and LR-10 had the lowest percentage of 13C transported to the cluster, with a reduced fruit set of about 60% when compared to LR-0. The severity of leaf removal reduced significantly fruit set and increased shoot apex sink strength at the expense of the cluster

Simulated microgravity induces nuclear translocation of Bax and BCL-2 in glial cultured C6 cells

Alterations in the control of apoptotic processes were observed in cells during space flight or under simulated microgravity, the latter obtained with the 3D-Random Positioning Machine (3D-RPM). Usually the proteins Bax and Bcl-2, act as pro- or anti-apoptotic regulators. Here we investigated the effects of simulated microgravity obtained by the 3D-RPM on cell viability, localization and expression of Bax and Bcl-2 in cultures of glial cancerous cells. We observed for the first time a transient cytoplasmic/nuclear translocation of Bax and Bcl-2 triggered by changing gravity vector. Bax translocates into the nucleus after 1 h, is present simultaneously in the cytoplasm after 6 h and comes back to the cytoplasm after 24 h. Bcl-2 translocate into the nucleus only after 6 h and comes back to the cytoplasm after 24 h. Physiological meaning, on the regulation of apoptotic event and possible applicative outcomes of such finding are discussed

A Hydrogenated amorphous silicon detector for Space Weather Applications

The characteristics of a hydrogenated amorphous silicon (a-Si:H) detector are presented here for monitoring in space solar flares and the evolution of large energetic proton events up to hundreds of MeV. The a-Si:H presents an excellent radiation hardness and finds application in harsh radiation environments for medical purposes, for particle beam characterization and in space weather science and applications. The critical flux detection threshold for solar X rays, soft gamma rays, electrons and protons is discussed in detail.Comment: 32 pages, 13 figures, submitted to Experimental Astronom