Characterization of carotenoid pigments in mature and developing kernels of selected yellow-endosperm sorghum varieties

Sorghum is a critical source of food in the semiarid regions of sub-Saharan Africa and India and a potential source of dietary phytochemicals including carotenoids. The objective of this study was to determine the carotenoid profiles of sorghum cultivars, selected on the basis of their yellow-endosperm kernels, at various developmental stages. Following extraction from sorghum flours, carotenoids were separated by high-performance liquid chromatography (HPLC) with diode array detection. Total carotenoid content in fully matured yellow-endosperm sorghum kernels (0.112-0.315 mg/kg) was significantly lower (p < 0.05) than that in yellow maize (1.152 mg/kg) at physiological maturity. Variation in total carotenoids and within individual carotenoid species was observed in fully mature sorghum cultivars. For developing kernels, large increases in carotenoid content occurred between 10 and 30 days after half bloom (DAHB), resulting in a peak accumulation between 6.06 and 28.53 microg of total carotenoids per thousand kernels (TK). A significant (p < 0.05) decline was noted from 30 to 50 DAHB, resulting in a final carotenoid content of 2.62-15.02 microg/TK total carotenoids. (all-E)-Zeaxanthin was the most abundant carotenoid, ranging from 2.22 to 13.29 microg/TK at 30 DAHB. (all-E)-Beta-carotene was present in modest amounts (0.15-3.83 microg/TK). These data suggest the presence of genetic variation among sorghum cultivars for carotenoid accumulation in developing and mature kernels.     

Metabolite profiling based on lipophilic compounds for quality assessment of perilla (Perilla frutescens) cultivars

Lipophilic compounds from Korean perilla ( Perilla frutescens ) seeds were characterized to determine the diversity among their phytochemicals and to analyze relationships between their contents. Twenty-four metabolites consisting of policosanol, phytosterol, tocopherol, and fatty acids were identified. The metabolite profiles were subjected to data mining processes, including principal component analysis (PCA), partial least-squares discriminate analysis (PLS-DA), and Pearson's correlation analysis. PLS-DA could distinguish between all cultivars except between Daesil and Daeyeup cultivars. Linolenic acid contents were positively correlated with β-sitosterol (r = 0.8367, P < 0.0001) and γ-tocopherol contents (r = 0. 7201, P < 0.001) among all perilla grains. The Daesil and Daeyeup cultivars appear to be good candidates for future breeding programs because they have simultaneously high linolenic acid, phytosterol, and tocopherol levels. These results demonstrate the use of metabolite profiling as a tool for assessing the quality of food.     

Antioxidant Capacity of Newly Developed Pigmented Rice Cultivars in Korea

The antioxidant capacity of newly developed and highly popular pigmented rice cultivars (black rice, Galsaekchalmi, Jeoktomi, Hongchalmi, and Nogwonmi) in South Korea was analyzed. The rice grains were ground into powder, extracted with 70% ethanol, filtered, and concentrated with a rotary evaporator. The samples were analyzed for phenolic, flavonoid, and phytic acid contents, free radical scavenging activity, reducing power, ferrous ion chelating ability, lipid peroxidation inhibition, and superoxide dismutase‐like activity. The ethanolic extracts from pigmented rice cultivars showed greater antioxidant activity than that of the normal white rice. The black rice exhibited the highest free radical scavenging activity, ferrous chelating ability, and total phenolic and flavonoid contents. The reducing power and phytic acid content were found to be highest in Hongchalmi cultivar. The inhibition of lipid peroxidation was markedly higher in Jeoktomi compared with the other rice samples. The Nogwonmi rice showed the lowest antioxidant activity among the pigmented varieties analyzed. These findings provide valuable information on the antioxidant potential of newly developed pigmented rice varieties and may assist plant breeders in the selection of cultivars for the development of new lines of rice with enhanced functional quality.     

Phytochemical Profile and Antiproliferative Activity of Dough and Bread Fractions Made from Refined and Whole Wheat Flours

Phytochemical profile (phenolic acids, carotenoids, and tocopherols) and antiproliferative properties of bread processing fractions, including the dough, crumb, and upper crust made from refined wheat and whole wheat flours were analyzed for two wheat cultivars. Ferulic acid, lutein, and α‐tocopherol were the predominant phenolic acid, carotenoid, and tocopherol, respectively, extracted from all fractions. The levels of all phytochemicals in whole wheat samples were over eightfold higher than their corresponding refined wheat samples. The concentrations of total phenolic acids (soluble and insoluble bound) were higher in the upper crust of refined (∼60–90%) and whole wheat (∼15–40%) breads than their corresponding dough fractions. However, the dough of whole wheat had higher levels of tocopherols and carotenoids compared with the crumb and upper crust, suggesting that phenolic acids were relatively stable during baking, whereas tocopherols (∼25–80%) and carotenoids (∼20–80%), were partially degraded. The antiproliferative activity of whole wheat bread extracts against HT‐29 cancer cells was weakly correlated with total phenolic acids but showed no correlations with total carotenoid and total tocopherol contents.     

Phytochemical profiles and antioxidant activity of wheat varieties

Whole grain consumption has been associated with reduced risk of chronic diseases, such as cardiovascular diseases and cancer. These beneficial effects have been attributed to the unique phytochemicals of grains that complement those found in fruits and vegetables. Wheat is one of the major grains in the human diet; however, little is known about the inherent varietal differences in phytochemical profiles, total phenolic and carotenoid contents, or total antioxidant activities of different wheat varieties, which ultimately influence the associated nutritional and health benefits of wheat and wheat products. The objectives of this study were to determine the phytochemical profiles and total antioxidant activity for 11 diverse wheat varieties and experimental lines. The profiles included free, soluble-conjugated, and insoluble-bound forms of total phenolics, flavonoids, and ferulic acids and carotenoid content including lutein, zeaxanthin, and beta-cryptoxanthin. The results showed that total phenolic content (709.8-860.0 micromol of gallic acid equiv/100 g of wheat), total antioxidant activity (37.6-46.4 micromol of vitamin C/g), and total flavonoid content (105.8-141.8 micromol of catechin equiv/100 g of wheat) did not vary greatly among the 11 wheat lines. However, significant differences in total ferulic acid content (p < 0.05) and carotenoid content (p < 0.05) among the varieties were observed, with carotenoid content exhibiting the greatest range of values. Carotenoid content among the 11 wheat varieties exhibited 5-fold, 3-fold, and 12-fold differences in lutein, zeaxanthin, and beta-cryptoxanthin, respectively. A synthetic wheat experimental line, W7985, gave the lowest carotenoid concentrations of any of the genotypes in this study. Such large genotypic differences in carotenoid content may open up new opportunities for breeding wheat varieties with higher nutritional value.     

Nondestructive prediction of total phenolics, flavonoid contents, and antioxidant capacity of rice grain using near-infrared spectroscopy

Phytochemicals such as phenolics and flavonoids, which are present in rice grains, are associated with reduced risk of developing chronic diseases such as cardiovascular disease, type 2 diabetes, and some cancers. The phenolic and flavonoid compounds in rice grain also contribute to the antioxidant activity. Biofortification of rice grain by conventional breeding is a way to improve nutritional quality so as to combat nutritional deficiency. Since wet chemistry measurement of phenolic and flavonoid contents and antioxidant activity are time-consuming and expensive, a rapid and nondestructive predictive method based on near-infrared spectroscopy (NIRS) would be valuable to measure these nutritional quality parameters. In the present study, calibration models for measurement of phenolic and flavonoid contents and antioxidant capacity were developed using principal component analysis (PCA), partial least-squares regression (PLS), and modified partial least-squares regression (mPLS) methods with the spectra of the dehulled grain (brown rice). The results showed that NIRS could effectively predict the total phenolic contents and antioxidant capacity by PLS and mPLS methods. The standard errors of prediction (SEP) were 47.1 and 45.9 mg gallic acid equivalent (GAE) for phenolic content, and the coefficients of determination ( r (2)) were 0.849 and 0.864 by PLS and mPLS methods, respectively. Both PLS and mPLS methods gave similarly accurate performance for prediction of antioxidant capacity with SEP of 0.28 mM Trolox equivalent antioxidant capacity (TEAC) and r (2) of 0.82. However, the NIRS models were not successful for flavonoid content with the three methods ( r (2) < 0.4). The models reported here are usable for routine screening of a large number of samples in early generation screening in breeding programs.     

Analysis of Genotype,Environment, and Their Interaction Effects on the Phytochemicals and Antioxidant Capacities of Red Rice (Oryza sativa L.)

Fourteen red rice varieties were planted in two locations during summer (Hangzhou) and winter (Hainan) to study the effect of genotype and environment on the phytochemicals and antioxidant capacities of rice grain. B‐type proanthocyanidins in red rice were detected by LC‐MS/MS and quantified by using the vanillin assay. Analysis of variance showed that total phenolic content (TPC), total flavonoid content (TFC) and 2,2′‐azino‐bis‐(3‐ethylbenzothiazoline‐6‐sulfonic acid) (ABTS) radical scavenging capacity were mainly affected by environmental factors, which accounted for more than 60% of the total variance. However, total proanthocyanidin content (TPAC) and 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical scavenging capacity were equally affected by both genotype and environment. The genotype × environment effects were significant for all traits. The pairwise correlations among TPC, TFC, TPAC, ABTS, and DPPH were also significant (r > 0.900, P < 0.001). Principal component analysis identified the genotypes that had higher contents of antioxidants and more stability across environments. This study showed that indirect selection of a simple trait (i.e., TPC) is an effective way to select rice high in antioxidant capacity in breeding programs. This study also suggests that rice should be produced specifically in a certain environment for the end user to minimize the variation in the functional properties and maximize their contents.     

Influence of Kernel Maturity,Milling Degree,and Milling Quality on Rice Bran Phytochemical Concentrations

Rice bran is a rich source of phytochemicals including tocopherols (T), tocotrienols (T3), and γ‐oryzanol that have purported positive effects on human health. The screening of germplasm to determine the genetic diversity influencing contents of these compounds requires knowledge of how sample preparation influences concentrations of the phytochemicals in rice bran. Obtaining this knowledge was the objective of this study. Cultivars with different milling qualities were all milled to different degrees. The differences in bran removal among cultivars decreased as the milling time increased. Samples that were milled for 30 and 40 sec (milled to the degree of 0.23–0.44% surface lipid content [SLC]) showed no significant differences in T and T3 concentrations in the bran within cultivars. Bran starch concentration affected the rankings of cultivars based on phytochemical contents. Expression of the γ‐oryanol concentration in bran after subtracting starch reduced the concentration differences resulting from differences in degree of milling (DOM). Bran from the mature thin kernels had phytochemical contents similar to that of the mature thick kernels milled for 30 sec. The immature thin kernels had significantly lower contents of most of the bran phytochemicals than did the mature kernel fractions.     

Carotenoids in white- and red-fleshed loquat fruits

Fruits of 23 loquat ( Eriobotrya japonica Lindl.) cultivars, of which 11 were white-fleshed and 12 red-fleshed, were analyzed for color, carotenoid content, and vitamin A values. Color differences between two loquat groups were observed in the peel as well as in the flesh. beta-Carotene and lutein were the major carotenoids in the peel, which accounted for about 60% of the total colored carotenoids in both red- and white-fleshed cultivars. beta-Cryptoxanthin and, in some red-fleshed cultivars, beta-carotene were the most abundant carotenoids in the flesh, and in total, they accounted for over half of the colored carotenoids. Neoxanthin, violaxanthin, luteoxanthin, 9- cis-violaxanthin, phytoene, phytofluene, and zeta-carotene were also identified, while zeaxanthin, alpha-carotene, and lycopene were undetectable. Xanthophylls were highly esterified. On average, 1.3- and 10.8-fold higher levels of colored carotenoids were observed in the peel and flesh tissue of red-fleshed cultivars, respectively. The percentage of beta-carotene among colored carotenoids was higher in both the peel and the flesh of red-fleshed cultivars. Correlations between the levels of total colored carotenoids and the color indices were analyzed. The a* and the ratio of a*/ b* were positively correlated with the total content of colored carotenoids, while L*, b*, and H degrees correlated negatively. Vitamin A values, as retinol equivalents (RE), of loquat flesh were 0.49 and 8.77 microg/g DW (8.46 and 136.41 microg/100 g FW) on average for white- and red-fleshed cultivars, respectively. The RE values for the red-fleshed fruits were higher than fruits such as mango, red watermelon, papaya, and orange as reported in the literature, suggesting that loquat is an excellent source of provitamin A.     

Effect of processing on the phytochemical profiles and antioxidant activity of corn for production of masa, tortillas, and tortilla chips

The phytochemical profiles (total phenolics, anthocyanins, ferulic acid, carotenoids) and antioxidant activities of five types of corn (white, yellow, high carotenoid, blue, and red) processed into masa, tortillas, and tortilla chips were studied. The nixtamalization process significantly (p < 0.05) reduced total phenolics and antioxidant activities when compared to raw grains. Nixtamalized grains exhibited higher concentration of free phenolics and soluble conjugated ferulic acid and had lower concentrations of bound phenolics and ferulic acid than unprocessed grains. Among processed products, there was little difference in the phytochemical contents and antioxidant activities. Among types of corn, the highest concentrations of total phenolics, ferulic acid, and antioxidant activity were observed in the high-carotenoid genotype followed by the regular yellow counterpart. The white corn contained the lowest amount of total phenolics and antioxidant activity. The pigmented blue corn had the highest anthocyanin concentration followed by the red counterpart. These findings suggest that lime-cooking significantly reduced the phytochemical content of nixtamalized products but released phenolics and ferulic acid.     

Cocoa has more phenolic phytochemicals and a higher antioxidant capacity than teas and red wine

Black tea, green tea, red wine, and cocoa are high in phenolic phytochemicals, among which theaflavin, epigallocatechin gallate, resveratrol, and procyanidin, respectively, have been extensively investigated due to their possible role as chemopreventive agents based on their antioxidant capacities. The present study compared the phenolic and flavonoid contents and total antioxidant capacities of cocoa, black tea, green tea, and red wine. Cocoa contained much higher levels of total phenolics (611 mg of gallic acid equivalents, GAE) and flavonoids (564 mg of epicatechin equivalents, ECE) per serving than black tea (124 mg of GAE and 34 mg of ECE, respectively), green tea (165 mg of GAE and 47 mg of ECE), and red wine (340 mg of GAE and 163 mg of ECE). Total antioxidant activities were measured using the 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assays and are expressed as vitamin C equivalent antioxidant capacities (VCEACs). Cocoa exhibited the highest antioxidant activity among the samples in ABTS and DPPH assays, with VCEACs of 1128 and 836 mg/serving, respectively. The relative total antioxidant capacities of the samples in both assays were as follows in decreasing order: cocoa > red wine > green tea > black tea. The total antioxidant capacities from ABTS and DPPH assays were highly correlated with phenolic content (r2 = 0.981 and 0.967, respectively) and flavonoid content (r2 = 0.949 and 0.915). These results suggest that cocoa is more beneficial to health than teas and red wine in terms of its higher antioxidant capacity.     

不同氮水平下粳稻的氮素累积和转运特征

Developing high-yielding rice （Oryza sativa L.） cultivars depends on having a better understanding of nitrogen （N） accumulation and translocation to the ear during the reproductive stage. Field experiments were carried out to evaluate the genetic variation for N accumulation and translocation in different Japonica rice cultivars at different N rates and to identify any relationship to grain yield in southeast China. Four Japonica cultivars with similar agronomic characteristics were grown at two experimental sites in 2004 with three N rates of 0, 60, and 180 kg N ha^-1. Dry weights and N contents of rice plants were measured at tillering, initiation, anthesis, and maturity. Grain yields exhibited significant differences （P 〈 0.05） among the cultivars and N application rates. Increasing N rates improved N uptake at anthesis and maturity in all four cultivars （P 〈 0.05）. N translocation from vegetative organs to the grains increased with enhanced N rates （P 〈 0.05）. N translocation to the grains ranged from 9 to 64 kg N ha^-1 and N-translocation efficiency from 33% to 68%. Grain yield was linear to N uptake at anthesis （r^2 = 0.78^＊＊） and N translocation （r^2 = 0.67^＊＊）. Thus, cultivars with a high N uptake at anthesis, low residual N in the straw at maturity, and appropriate low N fertilizer supply in southeast China should efficiently increase N-recovery rate while maintaining grain yield and soil fertility.     

Phytochemical composition, anti-inflammatory, and antiproliferative activity of whole wheat flour

Whole wheat flour from five wheat cultivars was evaluated for phenolic, carotenoid, and tocopherol compositions as well as anti-inflammatory and antiproliferative activities against HT-29 cells. The total ferulic acid content ranged from 452 to 731 μg/g among the five cultivars and was primarily present in the insoluble-bound form. Lutein was the only carotenoid detected and ranged from 1.5 to 4.0 μg/g, and α-tocopherol levels ranged from 12 to 61 μg/g. Extracts of four cultivars demonstrated significant anti-inflammatory activity, measured as inhibition of interleukin-1β (IL-1β) mRNA expression; however, none of the extracts inhibited tumor necrosis factor-α (TNF-α) mRNA expression, a second indicator of anti-inflammatory activity. Proliferation of HT-29 adenocarcinoma cells was inhibited by extracts from all cultivars at the dose of 100 mg botanical equivalent/mL. The cultivar WestBred 936 had the greatest antiproliferative activity at lower concentrations (20 and 50 mg botanical equivalent/mL), had the greatest anti-inflammatory effect against IL-1β, and also had the highest levels of ferulic acid and α-tocopherol. This research shows that whole wheat flours of these five cultivars varied significantly in their contents of phenolics, carotenoids, and α-tocopherol as well as in their anti-inflammatory and antiproliferative potentials, suggesting the possibility that wheat varieties can be selected based on potential health benefits.     

Carotenoid Composition and Changes in Sweet and Field Corn (Zea mays) During Kernel Development

Kernels of two carotenoid‐rich cultivars, sweet corn Jingtian 5 and field corn Suyu 29, were compared in terms of carotenoid composition during corn kernel development. The results showed that eight principal carotenoids were characterized by HPLC with diode array detection and atmospheric pressure chemical ionization tandem mass spectrometry with a C30 column. During kernel development, there was a similar trend in the change of total carotenoids for both corn cultivars, and the variation of individual carotenoids was also somewhat similar; violaxanthin, zeaxanthin, lutein, α‐cryptoxanthin, and β‐cryptoxanthin contents had upward trends, whereas neoxanthin content declined all the time, and α‐carotene and β‐carotene had no significant changes. However, the highest levels of the major carotenoids lutein (41.61 µg/g, dry weight) and zeaxanthin (39.59 µg/g, dry weight) obtained in field corn Suyu 29 during the milk stage were higher than those in sweet corn Jingtian 5, whereas the other individual carotenoid levels were significantly lower. Compared with the grain color, highly significant positive correlations were observed between zeaxanthin, lutein, and violaxanthin contents and deeper yellow/orange coloration indicators for field corn Suyu 29, but these relationships were weak for sweet corn Jingtian 5. Potential genetic variation might exist for carotenoid accumulation in sweet and field corn kernels.     

Carotenoid profiles and consumer sensory evaluation of specialty carrots (Daucus carota, L.) of various colors

Five different colored carrots were analyzed for their carotenoid profile and underwent sensory evaluation to determine consumer acceptance (n = 96). Four major carotenoids were identified and quantified by use of HPLC methods. High beta-carotene orange carrots were found to contain the greatest concentration of total carotenoids. Except for the white, all the carrots are a significant source of bioavailable carotenoids. Sensory evaluation showed the high beta-carotene orange and white carrots to be favored over the yellow, red, and purple carrots in both blind and nonblind treatments (P < 0.01). However, all the carrots were well accepted by the consumer panel. With this information, carrot growers should be encouraged to cultivate specialty carrots to provide sources of both vitamin A precursors and phytochemicals.     

Carotenoid content of 50 watermelon cultivars

The lycopene content of 50 commercial cultivars of seeded and seedless red-fleshed watermelons was determined. Scanning colorimetric and spectrophotometric assays of total lycopene were used to separate watermelon cultivars into low (<50 mg/kg fw), average (50-70 mg/kg fw), high (70-90 mg/kg fw), and very high (>90 mg/kg fw). Cultivars varied greatly in lycopene content, ranging from 33 to 100 mg/kg. Most of the seeded hybrid cultivars had average lycopene contents. Sixteen of the 33 seedless types had lycopene contents in the high and very high ranges. All-trans-lycopene was the predominant carotenoid (84-97%) in all watermelon cultivars measured by high-performance liquid chromatography, but the germplasm differed in the relative amounts of cis-lycopene, beta-carotene, and phytofluene. Red-fleshed watermelon genotypes vary extensively in carotenoid content and offer opportunities for developing watermelons with specifically enhanced carotenoids.     

Carotenoid Value Addition of Cereal Products by Monoculture and Mixed‐Culture Fermentation of Phaffia rhodozyma and Sporobolomyces roseus

Carotenoid value addition of corn whole stillage by red yeast fermentation has yielded astaxanthin‐ and β‐carotene‐enriched distillers dried grains with solubles (DDGS) for animal feed. In this study, commonly used animal feeds (rice bran, wheat bran, milo whole stillage, and soybean products) were subjected to carotenoid value addition. Phaffia rhodozyma and Sporobolomyces roseus monoculture and mixed‐culture submerged fermentation of these substrates supplemented with 5% glycerol were analyzed for astaxanthin, β‐carotene, and residual glycerol. Among all the substrates, full‐fat rice bran and full‐fat soy flour resulted in the highest astaxanthin (80 μg/g by P. rhodozyma) and β‐carotene yields (836 μg/g by S. roseus). P. rhodozyma produced the highest astaxanthin yield on each substrate, whereas depending on the substrate, either the mixed culture or S. roseus monoculture produced the highest β‐carotene yield. Soy hull was a poor substrate for carotenoid value addition. Both yeasts used glycerol as a carbon source for carotenoid production. This study shows that substrates influence the carotenoid yield. However, it is impossible to dissect the effect of specific nutrients on carotenoid production in complex biological substrates. Carotenoid value addition of these substrates provides as much as or more than the required daily dosage of carotenoids in animal feed.     

Genotype and Environment Effects on Tocopherol,Tocotrienol, and γ‐Oryzanol Contents of Southern U.S. Rice

Rice bran contains phytochemicals such as E vitamers (i.e., tocopherols and tocotrienols) and the γoryzanol fraction that reportedly may have positive effects on human health. Brown rice, rice bran, and rice bran extracts are therefore attractive candidates for use in the development of functional foods. The objectives of this project were to quantify the effects of genetics versus environment on the tocopherol, tocotrienol, and γ‐oryzanol contents of Southern U.S. rice and to determine associations between the levels of these phytochemicals. Seven rice cultivars grown in four states during two years were studied. Averaged across all samples, the content of α‐tocotrienol > γ‐tocotrienol > α‐tocopherol > gamma;‐tocopherol, and the tocopherols and tocotrienols were 27.5 and 72.5% of the total E vitamer content, respectively. Total E vitamer content ranged from 179 to 389 mg/kg and γ‐oryzanol from 2,510 to 6,864 mg/kg. A low correlation between total E vitamer and γ‐oryzanol contents suggests that to obtain rice bran with high levels of both of these fractions, new cultivars would need to be produced using hybridization and selection. In general, growing environment had a greater effect on E vitamer and γ‐oryzanol levels than did genotype. Therefore, rice breeders selecting genotypes with optimized levels of E vitamers and γ‐oryzanol will need to grow their breeding material in multiple years and locations.     

不同水分处理对烟草叶片高光谱及红边特征的影响

采用ASD Fieldspec HH光谱仪, 测定了不同水分处理下两个烟草品种叶片的光谱特性, 分析其红边特征参数的变化规律及其与烟叶生理指标的相关性。结果表明: 不同水分处理之间的烟草叶片光谱反射率差异明显, 但两个品种的变化规律一致。烟草伸根期和旺长期, 近红外光区的光谱反射率随土壤水分的增加而升高, 成熟期则呈相反趋势, 且光谱反射率在旺长期达到最高值。不同水分处理下烟草叶片一阶微分光谱趋势总体一致, 但红边一阶导数光谱差异显著。红边位置随土壤水分减少向长波方向移动, 发生“红移”现象。红边幅值和红边面积在伸根期和旺长期均随土壤含水量的增加而发生“红移”现象, 成熟期则发生“蓝移”现象。烟草叶片的红边位置同其生理指标的相关性要优于其他参数, 同叶绿素a含量、叶绿素b含量、类胡萝卜素含量、叶绿素总量、叶片鲜重、叶片干重、叶面积和叶片含水率均呈极显著相关关系; 红边幅值和红边面积与叶绿素a含量、叶绿素b含量、类胡萝卜素含量、叶绿素总量和叶片含水率之间均呈极显著性正相关, 红边面积同叶片干重呈极显著性负相关关系。     

水稻品种和砷污染对土壤溶解性有机碳氮的影响

选取有机质含量和pH不同的2种水稻土(黄泥田和红泥田),通过盆栽实验研究砷(As)污染条件下,种植9个水稻品种对土壤溶解性有机碳(DOC)和溶解性有机氮(DON)含量的影响,分析水稻品种、As污染和土壤类型的相对影响与交互作用.结果表明,水稻品种显著影响了土壤DOC和DON的变化,在水稻收获后,DOC平均含量的大小顺序为杂交稻(41.09±0.92 mg kg-1)＞籼稻(38.10±1.53 mg kg-1)＞粳稻(37.74± 1.37 mg kg-1);DON平均含量的大小顺序为粳稻(2.94± 0.40 mg kg-1)＞杂交稻(2.61±0.42 mg kg-1)＞籼稻(1.45± 0.17 mg kg-1).As污染降低了土壤DOC和DON的含量,但不同品种水稻的响应不同.与对照相比,As污染条件下,黄泥田和红泥田中DOC平均含量分别下降了14.4％和11.1％,DON平均含量分别下降了65.0％和44.7％;DOC在种植杂交稻后降幅最小,而DON在种植籼稻后降幅最小.在两种水稻土中,黄泥田的DOC和DON平均含量高于红泥田,在没有As污染条件下,分别高22.4％和45.8％,这与黄泥田有机质含量和pH高有关.水稻品种、As污染和土壤类型对DOC和DON变化的影响不同,3个因子对DOC变化的相对贡献率分别为7.7％、15.5％和27.6％,对DON变化的相对贡献率分别为14.7％、24.2％和2.0％.