Relationship of superficial scald development and alpha-farnesene oxidation to reactions of diphenylamine and diphenylamine derivatives in Cv. Granny Smith apple peel

Cv. Granny Smith apple fruit, treated at harvest with aqueous emulsions containing diphenylamine (DPA) and DPA derivatives, were evaluated for the peel disorder superficial scald (scald) after 6 months of cold storage at 1 degrees C plus 0 or 7 days at 20 degrees C. Metabolism of these derivatives and alpha-farnesene oxidation were also evaluated after 6 months. Derivatives substituted at the para position prevented scald, but scald developed on fruit treated with derivatives substituted in the amino, ortho, or meta positions. The extent of scald control was also dependent on the chemical nature of the functional group used to derivatize DPA. Hydroxylation of DPA and DPA derivatives during storage was not associated with scald control. Methoxylated DPA derivatives produced during storage resulted from O-methylation of C-hydroxylated derivatives rather than C-methoxylation of DPA. N-Nitrosodiphenylamine provided partial scald control, possibly resulting from its degradation to DPA, indicating that the amino hydrogen of DPA may be crucial for scald control. Results suggest that functional group position and chemical properties both contribute to the efficacy of DPA derivatives for scald control.     

Multivariate analysis of superficial scald susceptibility on Granny Smith apples dipped with different postharvest treatments

Multivariate methods were used to present the results of different postharvest treatments applied to control superficial scald disorder in Granny Smith apples. In a two-season study, the treatments applied by dips were diphenylamine (DPA), Semperfresh (a sucrose ester coating) formulated alone or with either ascorbyl palmitate or n-propyl gallate, and CaCl(2). DPA correlated negatively with scald, whereas the rest of the treatments showed no clear relationship with the disorder. By means of partial least squares, the incidence of superficial scald after cold storage was shown to correlate with quality parameters (firmness and acidity), measured at the end of storage. In contrast, ethylene production did not appear as a relevant factor in the incidence of scald.     

Relationships between volatile production, fruit quality, and sensory evaluation in Granny Smith apples stored in different controlled-atmosphere treatments by means of multivariate analysis.

Aroma compounds, quality parameters, and sensory evaluation of Granny Smith apples were analyzed after 3, 5, and 7 months of cold storage in three controlled-atmosphere (CA) treatments, in which oxygen and carbon dioxide were held at 1, 2, and 3%. During poststorage ripening, the apples were kept at 20 degrees C for 1, 5, and 10 days before analytical measurements were made. The highest volatile emission was obtained after 5 months of storage in all CA treatments, reaching its highest value when a low-oxygen CA (LO) was used. Ultralow-oxygen CA (ULO) showed the highest ability to maintain apple firmness. The correlation among analytical and sensory parameters suggests that ethyl 2-methylbutyrate, 1-butanol, pentyl acetate, and tert-butyl propionate are the aroma compounds with the highest influence in the sensorial score. Concerning CA treatments, LO and ULO appear to be very valuable technologies for maintaining the sensorial quality even after 7 months of storage.     

圆叶锦葵对Cd处理的光合生理响应及Cd富集特征

为揭示镉(Cd)处理下圆叶锦葵的光合耐性及其对Cd的富集特征,通过土壤盆栽试验,设置不同浓度Cd[0(CK)、5、15、30、60、100 mg·kg^-1]对圆叶锦葵进行处理,测定不同Cd浓度处理下圆叶锦葵的生长、光合参数、光合色素含量、抗氧化酶(SOD、CAT、POD、APX)活性及对Cd的富集能力。结果表明,Cd处理促进了圆叶锦葵的生长,30 mg·kg^-1 Cd处理下生物量达到最大值。Cd处理下,光合速率(Pn)、蒸腾速率(Tr)均呈先增加后降低的趋势,5~60 mg·kg^-1处理时Pn和Tr显著高于CK,100 mg·kg^-1Cd处理下的Pn和Tr显著低于CK。Cd处理下,叶绿素a含量增加,而叶绿素b、总叶绿素含量和类胡萝卜素含量呈先升高后降低的趋势,分别在5 mg·kg^-1和30 mg·kg^-1处理时达到最大值,Cd处理下的光合色素含量均显著高于CK。0~5 mg·kg^-1Cd处理下的光合作用受气孔因素和非气孔因素(叶面积、光合色素和抗氧化酶等)的影响;而5~100 mg·kg^-1处理下的光合作用主要受气孔因素的影响。随着 Cd 浓度的增加,圆叶锦葵根、茎、叶组织中 Cd 含量逐渐增加,其生物富集系数(BCF)和转运系数(TF)均大于1.0,BCF值在5 mg·kg^-1Cd处理时达到最大值,其对Cd具有较强的富集能力,TF值在100 mg·kg^-1Cd处理时显著升高,且达到最大值(7.37),其对Cd具有较强的转运能力;100 mg·kg^-1Cd处理下,圆叶锦葵根、茎、叶组织中Cd>100 mg·kg^-1DW。综上,圆叶锦葵对Cd具有较强的光合耐性和超富集能力,是一种潜在的超富集植物。本研究结果为挖掘新的植物修复材料提供了理论依据。     

Differential resistance of switchgrass <Emphasis Type="Italic">Panicum virgatum</Emphasis> L. lines to fall armyworms <Emphasis Type="Italic">Spodoptera frugiperda</Emphasis> (J. E. Smith)

Six cultivars of switchgrass Panicum virgatum L., a plant native to North America that has potential as a bioenergy source, were evaluated for resistance to feeding by the fall armyworm Spodoptera frugiperda (J. E. Smith). Although no mortality was noted, seedlings of the cultivar ‘Trailblazer’ and older plants of the cultivar ‘Blackwell’ were among the most resistant to feeding by S. frugiperda. Some field-collected samples from natural habitat were fed upon by S. frugiperda as readily as were the cultivars, while others caused high mortality after 2 days. Enzyme assays indicated relative differences in expression of two peroxidases thought to be involved in insect resistance in maize, but not in two chitinolytic enzymes. Genomic searches based on maize-sequence templates for the aforementioned genes identified homologs in switchgrass. Sequencing of cDNA coding for these genes identified some differences, especially in the cationic peroxidase, which could influence relative activity. These results indicate switchgrass germplasm has varying resistance to fall armyworms which could be a function of gene sequence diversity, as well as of variation in gene expression due to differences in ploidy levels or other factors.     

Influence of ethylene action, storage atmosphere, and storage duration on diphenylamine and diphenylamine derivative content of Granny Smith apple peel

The application of diphenylamine (DPA) to prevent the apple peel disorder superficial scald can result in accumulation of a number of DPA derivatives resulting from C-nitration, C-hydroxylation, O-methylation, and N-nitrosation during fruit storage. As the presence of these compounds may be indicative of metabolic processes leading to superficial scald development, the contents of DPA and DPA derivatives were determined in fruits treated at harvest with DPA or DPA plus the ethylene action inhibitor 1-methylcyclopropene (1-MCP), which also prevents scald development. Influences of fruit maturity, storage environment, storage duration, and a 14 day poststorage ripening period on accumulation of DPA metabolites were also assessed. Poststorage ripening, 1-MCP treatment, and controlled atmosphere storage had varied effects on DPA derivative contents suggesting that reactive oxygen and nitrogen species, such as *OH, *NO, and *NO2, or enzyme-catalyzed reactions may be present during certain ripening and senescence-related physiological processes. Definitive correlations between superficial scald incidence and contents of specific derivatives were not observed.     

Rapid preparation of procyanidins B2 and C1 from Granny Smith apples by using low pressure column chromatography and identification of their oligomeric procyanidins

Research in the field of procyanidins is always hindered by the lack of procyanidin standards, and the preparation of procyanidins, especially in large scale, remains difficult and time-consuming. Commercial sources of procyanidin standards are scarce. In this study, a rapid preparation method of procyanidins by using low-pressure column chromatography was developed. Procyanidins in Granny Smith apples were extracted with boiled water and purified on an ADS-17 macroporous resin column to obtain a Granny Smith apple procyanidin extract (GSE). GSE was fractionated according to its degree of polymerization on a Toyopearl TSK HW-40s column. Procyanidins B2 (epicatechin-(4beta-8)-epicatechin) and C1 (epicatechin-(4beta-8)-epicatechin-(4beta-8)-epicatechin) were prepared without HPLC separation. Oligomeric procyanidins from Granny Smith apples were also identified by liquid chromatography-electrospray ionization-mass spectrometry.