Cytokinin and abscisic acid alleviate drought stress through changing organic acids profile, ion immolation, and fatty acid profile to improve yield of wheat (Triticum aestivum L.) cultivars.

There is an increasing interest for plant hormones to modulate the harmful effects of drought on crops. The present study was conducted to assess the effect of foliar-applied cytokin (CK) and abscisic acid (ABA) on yield, organic acids, minerals, and fatty acid profile of wheat (Triticum aestivum L.) cultivars (MV17 and Pishgam) in response to drought stress. The results showed drought significantly decreased grain yield and biomass, but they were enhanced by CK and ABA application. Acetic acid increased under drought stress conditions, and the remarkable increase (~ twofold) in succinic acid content was observed with ABA application under drought stress in MV17 cultivar. In general, drought stress decreased malic acid, pyruvic acid, and citric acid, but CK enhanced them. The leaf accumulations of potassium (K+), calcium (Ca2+), magnesium (Mg2+), iron (Fe2+), and zinc (Zn2+) decreased by drought, where its reduction in MV17 was greater than Pishgam. However, an increased sodium (Na+) content was observed in plants experiencing drought with non-foliar application of ABA and CK. The plant growth hormones especially CK increased K+, Ca2+, Mg2+, Fe2+, and Zn2+, but decreased Na+. Fatty acid profile showed increased polyunsaturated fatty acids and monounsaturated fatty acids upon the drought stress. According to heat map, organic acids represented the maximum variations but fatty acids showed the minimum change during the treatments. The present study recommended foliar-applied CK to alleviate drought stress on wheat yield.

Impact of postharvest exogenous γ-aminobutyric acid treatment on cucumber fruit in response to chilling tolerance.

Low-temperature storage is generally used to extend postharvest lifetime and to inhibit decay of cucumber fruit, but it also enhances the intensity of chilling injury. The capability of γ-aminobutyric acid to enhance antioxidant enzyme activities and reduce chilling injury was studied in cucumber (Cucumis sativus L.) fruit stored at 1 °C for 5 weeks. The purpose of this study was to define if the GABA-induced modification in antioxidant system and phospholipase activity is linked to the reduced chilling injury in cold-stored cucumber fruit. Alleviation of chilling injury by GABA treatment was related to increased content of proline, endogenous GABA and enhanced activities of CAT and SOD, together with reduced activities of PLC, PLD and LOX. We suggest that PLC, LOX and PLD are associated with chilling injury initiation by involvement in a signaling pathway and membrane deterioration. Therefore the results obtained in this study suggest GABA's potential for postharvest applications for reducing chilling injury symptom in cucumber fruit.

Low-temperature acclimation related with developmental regulations of polyamines and ethylene metabolism in wheat recombinant inbred lines.

Winter survival is determined by complicated developmental regulations enabling wheat to adjust their transcriptome and metabolome to develop low temperature (LT) tolerance. The aim of the study was to clarify the metabolic responses developmentally regulated in six F6 recombinant inbred lines from a cross between Pishtaz (spring parent) and Mironovskaya 808 (winter parent). Spring genotypes, including pishtaz, RILs 4006 and 4014 showed lower LT tolerance, PAs (except the spermin), GABA and proline contents and DPPH• scavenging capacity. In these genotypes, genes and enzymes involved in the pathways of PAs and GABA degradation and ethylene biosynthesis were more active than other genotypes. RILs 4012 and 4016 with short vernalization displayed higher tolerance and lower H2O2 content compared to Pishtaz. Strong vernalization requirements in winter and facultative genotypes (Mironovskaya 808 parent and RILs 4003 and 4005) results in up-regulation of the metabolites and genes involved in PAs and GABA biosynthesis pathways (particularly when vernalization fulfillment occurred) to establish high tolerance as compared to genotypes without vernalization requirement. LT tolerance in all genotypes significantly decreased after vernalization fulfillment in February. Results indicated that LT tolerance was partly validated from developmental regulation of PAs, GABA, and ethylene metabolism during venalization and LT acclimation.

Investigation of thermal aspects of high-speed drilling of bone by theoretical and experimental approaches.

Heat generation during bone drilling operations is a serious challenge for the internal fixation surgery of bone fracture. Indeed, the heat generated at the drilling site causes complications including local temperature rise, thermal necrosis, irreversible damages to the bone tissue, and possible failure of orthopedic surgery. High-speed machining is an advanced method which has achieved remarkable results in some cases of reducing the temperature rise of the tool or workpiece. The present research examines high-speed drilling (HSD) of the bone using theoretical (based on Orthogonal Cutting theory and High-Speed Cutting model) and experimental (based on infrared thermography) approaches. The thrust force and temperature changes of the bone and drill bit have been measured at different rotational speeds. The drilling tests have been performed under a constant feed rate of 100 mm min-1, hole depth of 8 mm, and 18 rotational speeds of 1000-18,000 r min-1 (with 1000 r min-1 intervals) on a bovine femur. The results indicated that application of high rotational speeds in most cases caused increased temperature rise of the bone; only the rotational speed of 7000 r min-1 (which is associated with dramatic force reduction) and speed of 11,000 r min-1 (which is associated with alteration of the chip formation mechanism and its nature) resulted in the minimum extent of temperature rise in the bone. It was also observed that the High-Speed Cutting model was able to correctly estimate the threshold of high-speed machining range for the bone (5000 r min-1) and was also valid for the bone drilling operation.