Physiological responses to water deficiency in bread wheat (Triticum aestivum L.) lines with genetically different leaf pubescence

Studying the relationship between leaf pubescence and drought resistance is important for assessing Triticum aestivum L. genetic resources. The aim of the work was to assess resistance of common wheat genotypes with different composition and allelic state of genes that determine the leaf pubescence phenotype. We compared the drought resistance wheat variety Saratovskaya 29 (S29) with densely pubescent leaves, carrying the dominant alleles of the Hl1 and Hl3 genes, and two near isogenic lines, i: S29 hl1, hl3 and i: S29 Hl2aesp, with the introgression of the additional pubescence gene from diploid species Aegilops speltoides. Under controlled conditions of the climatic chamber, the photosynthetic pigments content, the activity of ascorbate-glutathione cycle enzymes and also the parameters of chlorophyll fluorescence used to assess the physiological state of the plants photosynthetic apparatus were studied in the leaves of S29 and the lines. Tolerance was evaluated using the comprehensive index D, calculated on the basis of the studied physiological characteristics. The recessive state of pubescence genes, as well as the introduction of the additional Hl2aesp gene, led to a 6-fold decrease in D. Under the water deficit influence, the fluorescence parameters profile changed in the lines, and the viability index decreased compared with S29. Under drought, the activity of ascorbate peroxidase, glutathione reductase and dehydroascorbate reductase in the line i: S29 hl1, hl3 decreased 1.9, 3.3 and 2.3 times, in the line i: S29 Hl2aesp it decreased 1.8, 3.6 and 1.8 times respectively, compared with S29. In a hydroponic greenhouse, line productivity was studied. Compared with S29, the thousand grains mass in the line i: S29 hl1, hl3 under water deficit was reduced. The productivity of the line i: S29 Hl2aesp was significantly reduced regardless of water supply conditions in comparison with S29. Presumably, the revealed effects are associated with violations of cross-regulatory interactions between the proteins of the trichome formation network and transcription factors that regulate plant growth and stress response

Effect of substrate thickness on ejection of phenylalanine molecules adsorbed on free-standing graphene bombarded by 10 keV C_{60}

Molecular dynamics computer simulations have been employed to investigate the effect of substrate thickness on the ejection mechanism of phenylalanine molecules deposited on free-standing graphene. The system is bombarded from the graphene side by 10 keV C_{60} projectiles at normal incidence and the ejected particles are collected both in transmission and reflection directions. It has been found that the ejection mechanism depends on the substrate thickness. At thin substrates mostly organic fragments are ejected by direct collisions between projectile atoms and adsorbed molecules. At thicker substrates interaction between deforming topmost graphene sheet and adsorbed molecules becomes more important. As this process is gentle and directionally correlated, it leads predominantly to ejection of intact molecules. The implications of the results to a novel analytical approach in Secondary Ion Mass Spectrometry based on ultrathin free-standing graphene substrates and a transmission geometry are discussed

SIMS instrumentation and methodology for mapping of co-localized molecules

We describe an innovative mode for localizing surface molecules. In this methodology, individual C60 impacts at 50 keV are localized using an electron emission microscope, EEM, synchronized with a time-of-flight mass spectrometer for the detection of the concurrently emitted secondary ions. The instrumentation and methodologies for generating ion maps are presented. The performance of the localization scheme depends on the characteristics of the electron emission, those of the EEM and of the software solutions for image analysis. Using 50 keV C60 projectiles, analyte specific maps and maps of co-emitted species have been obtained. The individual impact sites were localized within 1-2 μm. A distinctive feature of recording individual impacts is the ability to identify co-emitted ions which originate from molecules co-located within ∼10 nm

Statistics of Electron and Ion Emission from Single Massive Cluster Impacts

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