Change of physiochemical characteristics, nutritional quality, and volatile compounds of Chenopodium quinoa Willd. during germination.

The impacts of varying germination periods (0-72 h) on morphological properties, proximate composition, amino acid profile, GABA levels, antioxidant attributes, polyphenol content (both free and bound), and volatile compounds of quinoa were evaluated. Germination significantly increased the content of fiber, amino acids, GABA, polyphenols, and in-vitro antioxidant activities in quinoa. The optimal nutritional quality and antioxidant capacity of quinoa were observed during the 36-72 h germination period. We examined the dynamics of 47 phenolic compounds in quinoa during germination and noted a substantial rise in free phenolic acids and bound flavonoids post-germination. A total of 53 and 84 volatile compounds were respectively identified in ungerminated quinoa and germinated quinoa. It was found that the germination period of 24-48 h contributed to reducing the presence of undesirable flavors. TEM analysis revealed significant structural damage to the ultrastructure and relaxation of the cell wall in germinated quinoa grains.

[Pollution Characteristic and Control Factor Analysis of Atmospheric Ozone During Summer Typical Periods in Linyi, Shandong].

In June 2020, an observation experiment of O3 and its precursors was carried out in Linyi City, Shandong Province. Based on the observation data and MCM photochemical model simulation, the formation mechanism and control mechanism of an ozone pollution case in mid-June were analyzed. The study found that, despite the high precipitation during the observation period, ozone concentrations rapidly accumulated and exceeded the limits once the weather cleared, with the 1-h average and 8-h φ (O3) exceeding the national ambient air quality standards on 10 days (32% in frequency)and 14 days (45%), respectively. The diurnal variation in O3 concentration was unimodal and accompanied by the afternoon peak at 16:00. MCM simulation results showed that the daily net reaction rate of O3 was 20×10-9 h-1, and HO2·+NO and RO2·(except CH3O2·)+NO contributed 49.0%-51.1% and 37.3%-40.2% of O3 generation, respectively. The contribution of the·OH+NO2 reaction to the total consumption of O3 was 35.1%-57.4%. The results of VOCs reactivity, relative incremental reactivity (RIR), and the EKMA curve method showed that the generation of O3 was more sensitive to alkenes (mainly trans-2-pentene and trans-2-butene)and aromatics (mainly m/p-xylene and toluene)but was negatively sensitive to NOx. In other words, the reduction in VOCs concentration would lead to the decrease in O3 concentration, whereas the reduction in NOx concentration would lead to the increase in O3 concentration. PMF source analysis results showed that volatile sources used by solvents and vehicle exhaust emissions contributed significantly to the above key precursor VOC species. Considering the titration effect of NO from vehicle exhaust emissions on ozone, controlling the use of volatile sources of solvents can realize the control of O3 pollution accurately and efficiently.

Combined drought and bark beetle attacks deplete non-structural carbohydrates and promote death of mature pine trees.

How carbohydrate reserves in conifers respond to drought and bark beetle attacks are poorly understood. We investigated changes in carbohydrate reserves and carbon-dependent diterpene defences in ponderosa pine trees that were experimentally subjected to two levels of drought stress (via root trenching) and two types of biotic challenge treatments (pheromone-induced bark beetle attacks or inoculations with crushed beetles that include beetle-associated fungi) for two consecutive years. Our results showed that trenching did not influence carbohydrates, whereas both biotic challenges reduced amounts of starch and sugars of trees. However, only the combined trenched-bark beetle attacked trees depleted carbohydrates and died during the first year of attacks. While live trees contained higher carbohydrates than dying trees, amounts of constitutive and induced diterpenes produced did not vary between live and beetle-attacked dying trees, respectively. Based on these results we propose that reallocation of carbohydrates to diterpenes during the early stages of beetle attacks is limited in drought-stricken trees, and that the combination of biotic and abiotic stress leads to tree death. The process of tree death is subsequently aggravated by beetle girdling of phloem, occlusion of vascular tissue by bark beetle-vectored fungi, and potential exploitation of host carbohydrates by bark beetle symbionts as nutrients.

Larger Resin Ducts Are Linked to the Survival of Lodgepole Pine Trees During Mountain Pine Beetle Outbreak.

Periodic mountain pine beetle outbreaks have killed millions of hectares of lodgepole pine forests in western North America. Within these forests some pine trees often remain alive. It has been rarely documented whether anatomical defenses differ between beetle-killed and remaining live pine trees, especially at the northern latitudinal range of beetles in North America. In this study, we compared the resin duct-based anatomical defenses and radial growth between beetle-killed and live residual lodgepole pine trees, and we characterized the resin ducts and the growth of the residual trees before and after outbreak. We found that tree radial growth was not associated with tree survival. The best two predictors of tree survival were resin duct size and production (number per year). Trees having larger but fewer resin ducts showed higher survival probability compared to those with smaller but more abundant resin ducts annually. Residual trees had larger resin ducts prior to the outbreak and continued having so after the outbreak. We further categorized residual trees as healthy (having no signs or symptoms of insect or pathogen attacks), declining (with signs or symptoms of biotic attacks), and survived (from mountain pine beetle attacks during the outbreak) to investigate resin duct-based anatomical defenses among them. Healthy trees had consistently larger resin ducts than declining trees in the past 20 years in post-outbreak stands. Survival trees ranked between healthy and declining trees. Overall, these results demonstrate that resin duct size of lodgepole pine trees can be an important component of tree defenses against mountain pine beetle attacks and suggest that lodgepole pine trees with large resin ducts are likely to show resistance to future bark beetle attacks.

Weathering the storm: how lodgepole pine trees survive mountain pine beetle outbreaks.

Recent mountain pine beetle outbreaks in western North America killed millions of lodgepole pine trees, leaving few survivors. However, the mechanism underlying the ability of trees to survive bark beetle outbreaks is unknown, but likely involve phytochemicals such as monoterpenes and fatty acids that can drive beetle aggregation and colonization on their hosts. Thus, we conducted a field survey of beetle-resistant lodgepole pine (Pinus contorta) trees to retrospectively deduce whether these phytochemicals underlie their survival by comparing their chemistry to that of non-attacked trees in the same stands. We also compared beetle attack characteristics between resistant and beetle-killed trees. Beetle-killed trees had more beetle attacks and longer ovipositional galleries than resistant trees, which also lacked the larval establishment found in beetle-killed trees. Resistant trees contained high amounts of toxic and attraction-inhibitive compounds and low amounts of pheromone-precursor and synergist compounds. During beetle host aggregation and colonization, these compounds likely served three critical roles in tree survival. First, low amounts of pheromone-precursor (α-pinene) and synergist (mycrene, terpinolene) compounds reduced or prevented beetles from attracting conspecifics to residual trees. Second, high amounts of 4-allyanisole further inhibited beetle attraction to its pheromone. Finally, high amounts of toxic limonene, 3-carene, 4-allyanisole, α-linolenic acid, and linoleic acid inhibited beetle gallery establishment and oviposition. We conclude that the variation of chemotypic expression of local plant populations can have profound ecological consequences including survival during insect outbreaks.

Arabidopsis ein2-1 and npr1-1 response to Al stress.

An enhanced Al(3+) tolerance has been observed in ethylene insensitive mutant ein2-1 and salicylic acid insensitive mutant npr1-1 of Arabidopsis. However, we found that the tolerant phenotype of ein2-1 and npr1-1 under Al stress was dependent on NPR and EIN function, respectively, because the double mutant ein2-1/npr1-1 displayed more sensitive to Al stress than wild-type plants. We analysed the differential performance between ein2-1/npr1-1 and their respective single mutant in response to Al stress, and found that antioxidant defence rather than malate exudation was the determinant factor.