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The objective of this study was to set up a plant micropropagation facility to mass propagate sugarcane, energy cane, and related clonally propagated species. An efficient methodology for micropropagation of energy cane and perennial grasses using temporary immersion bioreactors was developed. Several different methods of tissue culture initiation, multiplication, and rooting were evaluated for several varieties of sugarcane (Saccharum officinarum L.) and sugarcane-related species such as Erianthus spp., Miscanthus spp., and Sorghum spp. × sugarcane hybrids, all from a germplasm collection. Apical meristem cultures were initiated for all genotypes that were micropropagated, when liquid or semisolid Murashige and Skoog (MS) medium was used, which was supplemented with 0.1–0.2 mg L−1 BAP, 0.1 mg L−1 kinetin, 0–0.1 mg L−1 NAA, and 0–0.2 μg L−1 giberellic acid. These cultures produced shoots between 4 and 8 wk after initiation. Shoot regeneration from leaf rolls or immature inflorescences was observed as early as 4 wk after initiation. Shoot multiplication was successful for all genotypes cultured in MS medium with 0.2 mg L−1 BAP and 0.1 mg L−1 kinetin. Energy cane had a significantly higher combined multiplication rate when grown under four or five LED lamps than when grown under three LED lamps, or under fluorescent lights in a growth chamber. The addition of 2 mg L−1 NAA produced faster and better rooting in all of the genotypes tested. Shoots produced well-developed roots after one cycle of 15–21 d in the bioreactors. The maximum number of plantlets produced per bioreactor was 1080. Plantlets developed a vigorous root system and were ready to be transplanted into the field after 2 mo. A protocol was standardized for different energy cane clones that were recommended for their biomass production and cell wall composition. Different tissues were used to speed up or facilitate tissue culture initiation. Visual assessment of micropropagated plants in the field did not show any off-types, based on gross morphological changes of plant morphology or disease reaction, compared to plants of the same genotype derived from a traditional propagation method (stem cuttings). This is the first report of energy cane and Miscanthus spp. micropropagation using the SETIS bioreactor.

Green nanotechnology is rapidly expanding in sustainable precision agriculture that promises to revolutionize food production. In the present study, nanoparticles (NPs) were synthesized using a gre...

Plants represent a safe and cost-effective platform for producing high-value proteins with pharmaceutical properties; however, the ability to accumulate these in commercially viable quantities is challenging. Ideal crops to serve as biofactories would include low-input, fast-growing, high-biomass species such as sugarcane. The objective of this study was to develop an efficient expression system to enable large-scale production of high-value recombinant proteins in sugarcane culms. Bovine lysozyme (BvLz) is a potent broad-spectrum antimicrobial enzyme used in the food, cosmetics and agricultural industries. Here, we report a novel strategy to achieve high-level expression of recombinant proteins using a combinatorial stacked promoter system. We demonstrate this by co-expressing BvLz under the control of multiple constitutive and culm-regulated promoters on separate expression vectors and combinatorial plant transformation. BvLz accumulation reached 1.4% of total soluble protein (TSP) (10.0 mg BvLz/kg culm mass) in stacked multiple promoter:BvLz lines, compared to 0.07% of TSP (0.56 mg/kg) in single promoter:BvLz lines. BvLz accumulation was further boosted to 11.5% of TSP (82.5 mg/kg) through event stacking by re-transforming the stacked promoter:BvLz lines with additional BvLz expression vectors. The protein accumulation achieved with the combinatorial promoter stacking expression system was stable in multiple vegetative propagations, demonstrating the feasibility of using sugarcane as a biofactory for producing high-value proteins and bioproducts.

Seed priming uses treatments to improve seed germination and thus potentially increase growth and yield. Low-cost, environmentally friendly, effective seed treatment remain to be optimized and tested for high-value specialty crop like watermelon (Citrullus lanatus) in multi-locations. This remains a particularly acute problem for triploids, which produce desirable seedless watermelons, but show low germination rates. In the present study, turmeric oil nanoemulsions (TNE) and silver nanoparticles (AgNPs) synthesized from agro-industrial byproducts were used as nanopriming agents for diploid (Riverside) and triploid (Maxima) watermelon seeds. Internalization of nanomaterials was confirmed by neutron activation analysis, transmission electron microscopy, and gas chromatography-mass spectrometry. The seedling emergence rate at 14 days after sowing was significantly higher in AgNP-treated triploid seeds compared to other treatments. Soluble sugar (glucose and fructose) contents were enhanced during germination in the AgNP-treated seeds at 96 h. Seedlings grown in the greenhouse were transplanted at four locations in Texas: Edinburg, Pecos, Grapeland, and Snook in 2017. At Snook, higher yield 31.6% and 35.6% compared to control were observed in AgNP-treated Riverside and Maxima watermelons, respectively. To validate the first-year results, treated and untreated seeds of both cultivars were sown in Weslaco, Texas in 2018. While seed emegence and stand establishments were enhanced by seed priming, total phenolics radical-scavenging activities, and macro- and microelements in the watermelon fruits were not significantly different from the control. The results of the present study demonstracted that seed priming with AgNPs can enhance seed germination, growth, and yield while maintaining fruit quality through an eco-friendly and sustainable nanotechnological approach.

Zinc is essential for the synthesis of amino acids, carbohydrates, and proteins, which are directly related to the chemical composition of raw coffee (Coffea arabica L.) beans, and it may influence the quality of the beverage. This study aimed at evaluating the influence of Zn doses on the chemical composition of coffee beans and beverage quality. Increased Zn availability in the growth medium maximized attributes related to beverage quality, such as polyphenol oxidase activity, color index, and contents of sucrose, caffeine, and trigonelline, reaching maximum values in plants with Zn leaf contents within the sufficiency range of 8.0 to 12.7 mg kg⁻¹. Zinc doses lower or higher than the one that provided maximum quality (∼2 μmol L⁻¹ in nutrient solution) increased the attributes related to loss of beverage quality, such as content of total phenols, 5-caffeoylquinic acid, leached K, and electrical conductivity. Zinc supply influences the quality of coffee beans, having a positive effect on polyphenol oxidase activity, color index, and contents of sucrose, caffeine, and trigonelline. Adequate Zn doses reduce total phenol content, 5-caffeoylquinic acid, leached K, and electrical conductivity. The leaf contents, which related to the minimum or maximum points of the quality attributes studied, varied between 8.0 and 12.7 mg Zn kg⁻¹.

The nutritional quality of many fruits and vegetables is regulated by pre-harvest management factors that can be manipulated to attain desired quality standards. In this study, the impact of seed nanopriming on the phytochemical composition of watermelon was studied. Seeds of two watermelon varieties namely: River Side (diploid) and Maxima (triploid) treated with two nanomaterials (silver nanoparticle and turmeric nanoemulsion) along with untreated seeds were grown in five locations over two seasons. Physico-chemical properties and phytochemical profiles were assessed after mature fruits were harvested and stored at 23 °C for 0, 10, and 20 d. Key physico-chemical characteristics that were impacted by storage included fruit weight, rind thickness, pH, and soluble solid content. Similarly, levels of health-promoting compounds such as carotenoids, l -citrulline, and total ascorbic acid were maintained and/or enhanced in watermelons after 10 d of storage compared to untreated fruits at harvest. However, l -citrulline (10.40 g/kg) and total ascorbic acid (57.52 g/kg) was significantly reduced in watermelons after 20 d of storage (8.6 and 19.09 g/kg, respectively) regardless of treatment and location (p

Melon (Cucumis melo L.) is an important diploid crop with a wide variety of flavors due to its distinct aromatic volatile organic compounds (VOC). To understand the development of VOC profiles during fruit development, we performed metabolomic and transcriptomic analysis of two cantaloupe varieties over the course of fruit development. A total of 130 metabolites were detected in fruit samples, and 449014207 reads were mapped to the melon genome. A total of 4469 differentially expressed genes in fruits were identified and used to visualize the transition of VOC and transcriptomic profiles during the fruit development. A shift of VOC profiles in both varieties was observed from early-fruit profiles enriched in C5-C8 lipid-derived VOCs to late-fruit profiles abundant in C9 lipid-derived VOCs, apocarotenoids, and esters. The shift coincided with the expression of specific isoforms of lipid and carotenoid metabolizing enzymes as well as transcription factors involved in fruit ripening, metabolite regulation, and hormone signaling.

The influence of spectral light on leaf quality and phytochemical contents and composition of aroma compounds in coriander leaves grown for fresh use under photo-selective nets; pearl net [40% shading; and 3.88 blue/red ratio; 0.21 red/far red ratio; photosynthetic radiation (PAR) 233.24 (μmolm(-2)s(-1))] and red net [40% shading and 0.57 blue/red ratio; 0.85 red/far red ratio; 221.67 (μmolm(-2)s(-1))] were compared with commercially used black nets [25% shading; 3.32 blue/red ratio 0.96 red/far red ratio; 365.26 (μmolm(-2)s(-1))] at harvest and after 14days of storage. Black nets improved total phenols, flavonoid (quercetin) content, ascorbic acid content, and total antioxidant activity in coriander leaves at harvest. The characteristic leaf aroma compound decanal was higher in leaves from the plants under the red nets at harvest. However, coriander leaves from plants produced under red nets retained higher total phenols, flavonoids (quercetin) and antioxidant scavenging activity 14days after postharvest storage (0°C, 10days, 95% RH and retailers' shelf at 15°C for 4days, 75% RH). But production under the pearl nets improved marketable yield reduced weight loss and retained overall quality, ascorbic acid content and aroma volatile compounds in fresh coriander leaves after postharvest storage. Pearl nets thus have the potential as a pre-harvest tool to enhance the moderate retention of phytochemicals and saleable weight for fresh coriander leaves during postharvest storage.

This study illustrates the effects of light quality as influenced by photo-selective shade nets (red, yellow, and pearl with 40% shade) and the widely used commercial black net (25% shade) on overall retail quality and phytochemical contents of three lettuce (Lactuca sativa L.) varieties (two green varieties, Ashbrook and Aquarell, and a red variety, Exbury) at after postharvest storage. Variety-specific responses were observed with respect to different coloured shade nets with regards to the accumulation of β-carotene, ascorbic acid, flavonoids (kaempferol, isorhamnetin, quercetin, myricetin, anthocyanin), and antioxidant activity at harvest. Growing var. Ashbrook under the pearl net improved the ascorbic acid and myricetin contents after postharvest storage. Var. Exbury (red) produced under the black net showed higher retention of ascorbic acid, and anthocyanin contents after postharvest storage. Also pearl net production improved the β-carotene content after postharvest storage in var. Aquarell...

Grapefruits grown under organic or conventional systems were analyzed for 6,7-dihydroxybergamottin (DHB) and flavanones using HPLC, and DPPH activity and ORAC using a micro-plate reader. Grapefruits harvested in November 2008 (E-1) and February 2010 (E-2) were stored at room temperature (RT) and 9 °C for four weeks. Higher levels of DHB were observed in conventional grapefruits during the second (4.7 ± 0.2 μg/g), third (1.5 ± 0.2 μg/g) and fourth (2.5 ± 0.2 μg/g) week of storage at room temperature in E2. Among flavonoids analyzed, narirutin (666.7 ± 33.9 μg/g), neohesperidin (17.5 ± 1.3 μg/g), didymin (75.5 ± 5.6 μg/g) and poncirin (130.8 ± 10.4 μg/g) levels were significantly higher (P⩽0.05) in organic grapefruits over conventional grapefruits at harvest and storage in E-1. Although DPPH levels were moderately correlated with grapefruit flavanone content, variability in the individual flavanone activity was pronounced, resulting in non-significant differences in antioxidant activity between organic and conventional grapefruits.

Identifying the rates of nitrate absorption by almond plants under water stress is important for improving nitrogen use efficiency in almond orchards. This study aimed to determine the rates of nitrate absorption by almond plants subjected to short-term water stress and no water stress, and the kinetic NO3− absorption parameters in well-watered three-year-old almond plants. Two assays were performed. In the first, fourteen plants arranged in completely randomized design received nutrient solutions with water potentials (Ψw) of 0.0, −0.2, −0.4 and −0.7 MPa and containing 1.2 mmol l−1 KNO3. We accessed the NO3− depletion in these solutions over an 8-h interval and estimated regression curves of the quantity of nitrate in the nutrient solution (Q) as a function of time (t). Subsequently nitrate uptake rates were calculated. Water loss; nitrate reductase activity; nitrate and total N of the sap; nitrate concentration of leaf dry matter; and nitrate and nitrite concentration of root dry matter were, either, evaluated. The second assay was performed the same way of the first one, with four well-watered plants submitted to 0.3 mmol l−1 KNO3 as initial concentration, and allowed estimating NO3− absorption parameters Vmax, Km and Cmin. We observed a linear decrease in the nitrate content of the containers receiving 1.2 mmol l−1 of NO3− over a period of 8 h. In this concentration, the rates of NO3− uptake ranged from 1.11 to 3.43 μmol g−1 h−1 and decreased in low water potentials at the root medium. Root nitrate reductase activity followed the same trend of nitrate absorption. In the low NO3− concentration range, the absorption showed a Michaelis–Menten pattern, being the kinetic parameters of NO3− absorption 1.15 ± 0.27 μmol g−1 h−1, 28.81 ± 4.12 μmol l−1 and 17.93 ± 1.1 μmol l−1 for Vmax, Km, and Cmin, respectively. We concluded that NO3− uptake of almonds is affected by short periods of water stress, with harmful effects occurring at Ψw below −0.18 MPa.

Photoselective shade netting technology is an emerging agrotechnological concept, which aims at combining physical crop protection with different filtrations of solar radiation. They are based on the incorporation of various chromatic additives, light dispersive and reflective elements into the netting materials during manufacturing. Postharvest quality of fresh produce is influenced by environmental conditions that include light, average temperature, minimum temperature, and night–day temperature difference. Photoselective shade nets have been shown to influence yield and quality parameters of fresh produce, their impacts on functional properties of vegetables after postharvest storage has not been fully investigated. Therefore, this chapter illustrates the effect of different colored photoselective shade nets (pearl, red, and yellow) in comparison to the commercially used black net on vegetables, such as tomatoes and sweet overall quality parameters (weight, SSC, and TA), bioactive compounds (ascorbic acid, total phenols, flavonoids, β-carotene, and lycopene contents), antioxidant scavenging activity, volatile aroma compounds at harvest and after postharvest storage.

Micronutrients perform specific and essential functions in plant metabolism, and their deficiency may lead to metabolic disturbances that affect coffee production and quality beverage. In Brazil, the B, Cu, and Zn are the main micronutrients, and these are provided by soil or foliar fertilization, frequently with low recovery efficiency. This work objected verifying the feasibility of supplying of B, Cu, and Zn via insertion of tablets in the orthotropic branch of Coffea arabica, as well as to evaluate the coffee plant response in terms of productivity and quality of the beverage. Adult plants received B, Cu, and Zn, each micronutrient alone or combined with the other two, by foliar fertilization or by tablets inserted in the trunk base. The productivity, cupping quality, and some chemical indicators of beans quality were evaluated in two crop seasons. Boron, copper, and zinc supplied by foliar spray or solid injections in the trunk influenced the chemical composition and quality of the coffee beans, characterized by the cupping test and the levels of caffeine, trigonelline, sucrose, glucose, arabinose, mannose, 3-caffeoylquinic acid, 5-caffeoylquinic acid, polyphenol oxidase activity, and total phenolic compounds. Copper and zinc were equivalent in either form of supply regarding the production and quality of coffee.

This study was designed to characterize morphological, physiological and molecular responses of sugarcane genotypes to a simulated water deficit stress. Two genotypes (TSP05-4: Drought-tolerant; TCP02-4589: Drought-sensitive) were subjected to a 20-day water deficit treatment and an 8-day recovery period. Leaf photosynthesis (Pn), transpiration rate (E), stomatal conductance (Gs), leaf greenness index (SPAD) and variable-to-maximum chlorophyll a fluorescence ratio (Fv/Fm), were evaluated before, during and after water deficit. Root-to-shoot ratio (R/S), stalk height (SH), diameter (SD) and stalk weight (SW) were evaluated at the end of the experiment. Real-time RT-PCR confirmed seven differentially-expressed transcript-derived fragments (TDFs) identified by cDNA-AFLP. Pn rates were similar between the genotypes under well-watered conditions. However, under water deficit, TSP05-4 had higher Pn rates. SPAD, Fv/Fm and R/S were also generally higher in TSP05-4, regardless of soil moisture status. Water deficit-induced reductions in SH and SW were greater in TCP02-4589 than in TSP05-4. Three TDFs showing sequence similarities to genes encoding a putative expressed pentatricopeptide, a protein kinase CK2 regulatory subunit CK2β3, and a glucose-6-phosphate/phosphate translocator 2 were identified in TCP02-4589. One TDF similar to a drought-inducible protein was identified in TSP05-4. Recovery of physiological processes and gene expression patterns to the water stress levels was fast. Key words: Differential gene expression, water deficit stress, re-watering, Saccharum spp.

Postharvest responses of red ('HTSP-3') and yellow ('Celaya') sweet pepper fruit yield, quality parameters and bioactive compounds (to three types of photo-selective nets and a standard black net) were investigated in this study. Red and yellow peppers produced under the black net retained higher β-carotene, lower total phenolic contents and showed deep red and orange colour after storage. Both peppers produced under the pearl net retained a higher ascorbic content, antioxidant scavenging activity, fruit firmness and also reduced weight loss after storage. Red and yellow peppers grown under pearl and yellow nets resulted in a higher percentage of marketable fruit, after storage. Red pepper grown under the yellow net showed a higher number of odour active aroma compounds in the fruit, while black nets significantly affected the synthesis of odour active aroma compounds during storage. Sensory analysis indicated a preference for red pepper fruits after storage from plants grown under pearl nets.

Huanglongbing is a devastating disease of citrus. In this study, a comprehensive profile of phloem sap amino acids (AA) in four permissive host plants of Candidatus Liberibacter asiaticus (CLas) and three non-permissive Rutaceae plants was conducted to gain a better understanding of host factors that may promote or suppress the bacterium. The AA profiles of Diaphorina citri nymphs and adults were similarly analyzed. A total of 38 unique AAs were detected in phloem sap of the various plants and D. citri samples, with phloem sap of young shoots containing more AAs and at higher concentrations than their mature counterparts. All AAs detected in phloem sap of non-permissive plants were also present in CLas -permissive hosts plus additional AAs in the latter class of plants. However, the relative composition of 18 commonly shared AAs varied between CLas -permissive hosts and non-permissive plants. Multivariate analysis with a partial least square discriminant methodology revealed a total of 12 AAs as major factors affecting CLas host status, of which seven were positively related to CLas tolerance/resistance and five positively associated with CLas susceptibility. Most of the AAs positively associated with CLas susceptibility were predominantly of the glutamate family, notably stressed-induced AAs such as arginine, GABA and proline. In contrast, AAs positively correlated with CLas tolerance/resistance were mainly of the serine family. Further analysis revealed that whereas the relative proportions of AAs positively associated with CLas susceptibility did not vary with host developmental stages, those associated with CLas tolerance/resistance increased with flush shoot maturity. Significantly, the proline-to-glycine ratio was determined to be an important discriminating factor for CLas permissivity with higher values characteristic of CLas -permissive hosts. This ratio could be exploited as a biomarker in HLB-resistance breeding programs.

Bioactive compounds in plant-derived foods provide essential human health benefits. However, the content and types of bioactive compounds may vary based on genetic and environmental factors. The present study examined the impacts of cultivar, fruit maturity stage (mature versus immature), and growing season (2008, 2009) on the concentration of bioactive compounds in diverse pungent and non-pungent peppers. Significant interactions were observed among cultivars, maturity stages, and growing seasons. Mature peppers generally had the highest content of ascorbic acid (782.0–2305.3 μg/g FW in 2008 and 693.5–2817.2 μg/g FW in 2009), and capsaicinoids (115.5–338.9 μg/g FW in 2008 and 93.8–326.3 μg/g FW in 2009) compared to immature peppers. Paprika-type peppers generally had the highest contents of ascorbic acid and flavonoids especially in mature fruits, while capsaicinoids were higher in all mature stage peppers. Flavonoid concentrations varied considerably depending on cultivar and maturity stage. Total phenolics were also significantly higher in mature fruits compared to immature peppers in both years. A positive correlation between total phenolics and DPPH radical scavenging activity was observed. This indicates that the health beneficial components in peppers could also vary as a function of cultivar, fruit developmental stage and production season. The genetic variability in bioactive compounds found in this study constitutes a useful genetic base for improving the nutrient quality of peppers.

Grapefruit heterocyclic oxygenated compounds have demonstrated antimicrobial and cytotoxic properties; purifying these compounds is essential for systematic biological studies to elucidate their bioactive properties. In the current study, a new method was used to isolate and purify coumarins from grapefruit oil and peels. Grapefruit oil was fractionated into volatile and non-volatile fractions (NVFs) by vacuum distillation. The NVF was further partitioned into hexane soluble and hexane insoluble fractions (HIFs). Then, the NVF–HIF composite was subjected to a hyphenated chromatography and separations were performed using a C-18 reversed phase column to yield several compounds. Additionaly, grapefruit peel was extracted with hexane and five compounds were purified using a normal phase silica column using hyphenated chromatography. Structures of the purified compounds were elucidated by 1 H and 13 C attached proton test (APT) NMR spectral data and identified as pranferin ( 1 ), meranzin ( 2 ), bergapten ( 3 ), dihydroxybergamottin ( 4 ), and marmin ( 9 ). Compounds ( 5–8 ) were later identified as heptamethoxy flavone, auraptene, osthol and nobilitin by comparing retention times in HPLC and mass spectra. With this method, it was possible to selectively separate major compounds from minor bioactives prior to hyphenated chromatography. This approach of solvent partitioning and rapid hyphenated chromatography proved highly effective in isolating several compounds, including pranferin from grapefruit oil.

Genetic diversity is present in the Capsicum genus for fruit size, shape, color, length, firmness, flavor, and even concentrations of different phytochemicals. Our goal in this study was to gain a better understanding of the relative ease of incorporating these characteristics into an improved cultivar evaluating a combination of 29 F1 paprika and serrano pepper (Capsicum annuum) hybrids along with 19 of their respective parents. Genotypes were grown and evaluated at the Texas AgriLife Research Center in Weslaco in the spring of 2008. Results confirmed our hypotheses that paprika type material have higher ascorbic acid (AA) and flavonoid (quercetin and luteolin) concentrations, while serrano peppers have higher expression of capsaicinoids (capsaicin and dihydrocapsaicin). We were also able to identify how productive certain hybrid combinations were at expressing a significant amount of positive heterosis for particular traits. From our Pearson's correlation analyses, we were able to identify the existence of a significant association between such comparisons as fruit weight with fruit diameter, fruit weight with fruit length, and fruit diameter with fruit length. Interestingly, we were also able to identify the presence of a significant association between such comparisons as ascorbic acid with fruit weight, ascorbic acid with fruit length, ascorbic acid with fruit diameter, total flavonoids with fruit weight, and total flavonoids with fruit length. This information, henceforth, allowed us to acknowledge the amount of variability present between these comparisons. In all, our results were able to reveal how effective certain combinations of parent material are toward production of F1 offspring exhibiting improved fruit traits and elevated phytochemical concentrations. Ideally, these results will serve as benchmarks for breeders interested in development of improved lines for these traits.

SUMMARYThe relationships between physiological variables and sugarcane productivity under water deficit conditions were investigated in field studies during 2005 and 2006 in Weslaco, Texas, USA. A total of 78 genotypes and two commercial varieties were studied, one of which was drought-tolerant (TCP93-4245) and the other drought-sensitive (TCP87-3388). All genotypes were subjected to two irrigation regimes: a control well-watered treatment (wet) and a moderate water-deficit stress (dry) treatment for a period of 90 days. Maximum quantum efficiency of photosystem II (Fv/Fm), estimated chlorophyll content (SPAD index), leaf temperature (LT), leaf relative water content (RWC) and productivity were measured. The productivity of all genotypes was, on average, affected negatively; however, certain genotypes did not suffer significant reduction. Under water deficit, the productivity of the genotypes was positively and significantly correlated with Fv/Fm, SPAD index and RWC, while LT had a negative correlation. These findings suggest that genotypes exhibiting traits of high RWC values, high chlorophyll contents and high photosynthetic radiation use efficiency under low moisture availability should be targeted for selection and variety development in programmes aimed at improving sugarcane for drought prone environments.

The development of simultaneous extraction and determination of bioactive molecules from natural products is becoming more popular. The present study reports the development of a method for the simultaneous extraction and determination of both capsaicinoids and ascorbic acid in peppers. Capsaicin (341.61 µg/g), dihydrocapsaicin (119.91 µg/g) and ascorbic acid (2,109.60 µg/g) were extracted with 3% metaphosphoric acid-ethanol (2:8) as a solvent. The efficient extraction of capsaicinoids (412.61 µg/g) and ascorbic acid (2,785.93 µg/g) was achieved at a sample-to-solvent ratio of 1:8 after 30 minutes of sonication. Simultaneous separation of capsaicinoids and ascorbic acid was achieved using a Gemini C18 column with a gradient elution of 0.03M phosphoric acid and methanol. Capsaicinoids and ascorbic acid were simultaneously detected at 282 and 254 nm, respectively. The recovery of capsaicinoids ranged from 96.21 to 108.71%, and the recovery of ascorbic acid ranged from 97.01 to 98.83%. The limits of detection for capsaicin, dihydrocapsaicin and ascorbic acid were 0.24, 0.21 and 0.26 µg, respectively. Relative standard deviation for the intra-day and inter-day variability in the results was less than 3%, indicating that the method produced highly reproducible results. Therefore, this method enables the reproducible, simultaneous separation and quantification of capsaicinoids and ascorbic acid from peppers.

Ascorbic acid (AA) and dehydroascorbic acid (DHA) are reduced and oxidized forms of vitamin C, which are ubiquitously found in various fruits and vegetables. The present study has evaluated and optimized various factors responsible for AA and DHA stability in grapefruit samples. Furthermore, the optimized method was used to quantify these compounds in different fruits and vegetables. The AA stability in the samples was evaluated by extracting grapefruit juice using 1, 3 and 5 g/100 mL metaphosphoric acid (MPA) and trichloro acetic acid (TCA). The AA levels were stable in grapefruit samples extracted with 1, 3 and 5 g/100 mL MPA, whereas TCA extracts showed degradation in 48 h. Among the three reducing agents studied, tris(2-carboxy ethyl) phosphine hydrochloride (TCEP) has efficiently converted DHA at all concentrations and the samples were stable for 48 h at 2.5 mmol/L TCEP. Lower pH favored complete conversion of DHA by TCEP than dithiothreitol. Among various fruits and vegetables analyzed, the highest levels of AA (260.1 mg/100 g) were observed in guava and DHA (58.6 mg/100 g) in parsley samples. The current optimized method prevents the degradation of AA and DHA from fruit and vegetable samples stored at room temperature for two days.

Bioactive compounds in foods have been shown to maintain human health. However, the relative amounts of bioactive compounds and the variation in the amounts are still poorly understood. In this study, the efficacy of different extraction solvents (hexane, ethyl acetate, acetone, methanol, and a methanol:water mixture), as well as the levels of certain bioactive compounds in non-pungent pepper cultivars (TMH, TMJ, PA137, and B58) were investigated using high-performance liquid chromatography (HPLC). Antioxidant activities were determined using 2,2,-diphenyl-1-picrylhydrazyl (DPPH), reducing power, and deoxyribose degradation. Hexane extracts had the highest level of carotenoids (47.2-628.8 μg/g), and methanol extracts contained maximum flavonoids (24.9-152.2 μg/g) in four different cultivars. Higher DPPH scavenging activity was found in the hexane extracts from TMH, TMJ, PA137, and B58 (IC₅₀ value: 0.67, 0.74, 0.55, and 0.48 μg/ml, respectively), whereas the reducing power was high in ethyl acetate and acetone extracts. Inhibition of deoxyribose degradation was highest in methanolic extracts from TMH, TMJ, PA137, and B58 (51.2, 49.5, 52.6, and 47.4 %, respectively). These data demonstrate that solvent chemical properties such as polarity can differentially impact the efficiency with which different bioactive compounds are recovered from foods, and this could lead to differences in estimated biological activity such as antioxidant capacity.

Habanero peppers have become increasingly popular in the United States for supplying unique flavors and high levels of pungency. As consumption of this product increases, development of improved cultivars with elevated phytochemicals will likely result in additional demand from consumers. This study evaluated fruit size, capsaicinoid, and flavonoid concentrations in six Habanero (Capsicum chinense) genotypes grown at three different Texas locations: College Station, Uvalde, and Weslaco. Five of these Habanero experimental hybrids (H1-red, H2-orange, H3-orange, H5-dark orange, and H6-yellow) were developed at Texas A&M University with genetic improvement in numerous traits of interest, and Kukulkan F1 (Kuk-orange) was included as a commercial control. In general, H1-red had the largest fruits in these locations. Capsaicin and dihydrocapsaicin (DHC) concentrations were highest in Kuk-orange followed closely by H5-dark orange and were lowest in H6-yellow. Fruit at Weslaco was larger and contained more capsaicin and DHC than those produced in Uvalde or College Station. Although flavonoid contents were variable and low in all genotypes and locations, H3-orange showed the most stability for use in future crossing schemes to compete against Kuk-orange for this characteristic. Our results suggest that variation in phytochemicals in fruit tissue of Habanero genotypes can be exploited by selecting in an appropriate environment.

Efficient extraction procedures including solvent selection, sample to solvent ratio, extraction time, and hydrolysis condition were developed for the analysis of flavonoids in peppers. Maximum flavonoids were extracted in ethanol, while N - N -dimethylformamide was able to extract myricetin, which was rarely reported in peppers. Flavonoids were obtained at the 1:8 ratio of sample to solvent after 3 h of extraction time. The effective hydrolysis of glycosides to aglycones was observed in 3 M HCl at 60 min at 95 °C. The validated HPLC method was applied to quantify five flavonoids from peppers. The ethanol extract exhibited maximum total phenolics (1.39 mg of catechin equivalent/g), and the DPPH assay showed a similar free radical scavenging activity in MeOH, EtOH, and EtOH:water (80:20). Reducing property of the MeOH extract was higher than the EtOH extract. This study demonstrated that the developed methods for the extraction of pepper flavonoids could be useful for analysing large numbers of samples.

Two greenhouse experiments were conducted to quantify growth responses ofJatropha curcasto a range of salt and drought stresses. Typical symptoms of salinity stress such as leaf edge yellowing were observed in all elevated salinity treatments and the degree of the foliar salt damage increased with the salinity of irrigation water. Total dry weight (DW) of Jatropha plants was reduced by 30%, 30%, and 50%, respectively, when irrigated with saline solutions at electrical conductivity of 3.0, 6.0, and 9.0 dSm−1compared to that in the control. LeafNa+concentration was much higher than that observed in most glycophytes. LeafCl−concentrations were also high. In the drought stress experiment, plants were irrigated daily with nutrient solution at 100%, 70%, 50%, or 30% daily water use (DWU). Deficit irrigation reduced plant growth and leaf development. The DW of leaves, roots, and total were reduced in the 70%, 50%, and 30% DWU compared to the 100% DWU control treatment. In summary, salinity stress and deficit irrigation significantly reduced the growth and leaf development of greenhouse-grown Jatropha plants.

The physiological response of four commercial sugarcane genotypes to water stress was evaluated by measuring the photochemical efficiency of the photosystem II (chlorophyll a fluorescence ratio, F v/F m), estimated chlorophyll content (SPAD unit), leaf temperature (LT) and leaf relative water content (RWC). A field trial was established in the subtropical area with well-watered and water-stressed genotypes, in completely randomized blocks with four replicates in a 4 × 2 × 3 factorial design (genotype × irrigation × evaluation date). Physiological measurements were done during a 90 day-period of formative stage of plants. The analysis of variance showed that the interaction of genotype × irrigation × evaluation date had a significant effect for three physiological markers tested, F v/F m, SPAD unit and RWC. Under non-stressed conditions, all genotypes showed similar responses for the four markers. Under water deficiency stress, two drought-tolerant genotypes, HOCP01-523 and TCP89-3505 displayed higher values for F v/F m, SPAD unit and RWC, and lower values for LT, and could be classified as tolerant. It is therefore possible to use these physiological water stress associated traits as scorable marker traits for selecting drought-tolerant sugarcane genotypes in future breeding programs.

Sulfur (S) nutrition has a strong influence on onion pungency, and the production of sweet onions in the high-sulfur soil of Texas is a challenge to growers. This study was performed to determine the effects of S applications to fields already having sufficient levels of soil S on pungency and related compounds in four shortday onion cultivars. The onion cultivars ‘Cougar’, ‘Legend’, ‘Texas Early White’, and ‘Texas Grano 1015Y’ were grown in three commercial fields at Edinburg, Mercedes, and Weslaco of the Rio Grande Valley of South Texas with applications of sulfur at 0, 13, and 26 kg S/ha. Pyruvic acid, bulb weight, extractable S in soil and total S in bulb, soluble solids content (SSC), flavor precursor compounds [also called S-alk(en)yl- l -cysteine-sulfoxides (ACSOs)], and total sugars were measured. The pyruvic acid level of onions was not increased by the S applications and showed no significant correlation with soil S levels in any of the cultivars at locations having 30 or 235 ppm S. The SSC, total S in bulbs, total sugars, and total ACSO content also showed no correlation with the S applications and soil S levels. Onion pungency and content of flavor precursor compounds were significantly influenced by cultivar and cultivar × location interaction. We conclude that onion pungency is not increased by application of extra S fertilizer to commercial fields already containing sufficient levels of soil sulfur.

Among the many plant mineral nutrients, potassium (K) stands out as a cation having the strongest influence on quality attributes that determine fruit marketability, consumer preference, and the concentration of critically important human-health associated phytonutrients. However, many plant, soil, and environmental factors often limit adequate uptake of K from the soil in sufficient amounts to satisfy fruit K requirements during development to optimize the aforementioned quality attributes. The objectives of this review are 1) to summarize published study abstracts on the effects of soil and/or foliar K fertilization as well as diverse K forms, on fruit phytonutrient concentrations; and 2) to illustrate the important role of K forms on fruit quality with a case study of Cucumis melo L (muskmelon) fruit produced with optimal soil applied K . The muskmelon studies will compare commercial sources (forms) of K applied to examine seasonal effects (spring vs. autumn) and the number of foliar K applications during fruit development on fruit marketability (maturity, yield, firmness, soluble solids, sugars, relative sweetness), consumer preference attributes (sugar content, sweetness, texture), and phytochemical concentrations (K, ascorbic acid, and β-carotene concentrations). Numerous studies have consistently demonstrated that specific K fertilizer forms, in combination with specific application regimes, can improve fruit quality attributes. Potassium fertilizer forms in order of effectiveness (Glycine (Gly)-complexed K = K2SO4 ≥ KCl > no K > KNO3) when applied wet (foliar or hydroponic) vs. dry (soil) were generally superior in improving fruit marketability attributes, along with many human-health nutrients. The muskmelon case study demonstrated that two K forms: Gly-complexed K and K2SO4, combined with a silicone-based surfactant, applied weekly, as a foliar spray, during fruit development, from both autumn and spring-grown plants, had the greatest impact on improving fruit marketability attributes (maturity, yield, firmness, and sugars), as well as fruit quality attributes (human-health bioactive compounds K, ascorbic acid, and β-carotene). Among several foliar applied K salts studied under field conditions so far, salts with relatively low salt indices appeared to have the greatest impacts on fruit quality when applied during the mid- to late-season fruit development periods.

The Zebra chip (ZC) syndrome is an emerging disease of potato and a major threat to the potato industry. The potato psyllid, Bactericerca cockerelli (Sulc) is believed to be a vector of the ZC pathogen, which is now thought to be Candidatus Liberibacter, a bacterium. To further understand the relationship between potato psyllid infestation and ZC disease expression, healthy potato plants at different growth stages (4, 6 and 10 weeks after germination) were exposed separately to potato psyllids that were separately reared on four solanaceous hosts plants (potato, tomato, eggplant or bell pepper) for more than 1 year. ZC symptoms, leaf rates and total nonstructural carbohydrate accumulation in leaves and tubers of healthy and psyllid-infested plants were monitored and recorded. Typical ZC symptoms were observed in leaves and tubers of all plants exposed to potato psyllids regardless of the host plant on which they were reared. This was also accompanied by significant reductions in net photosynthetic rate. Caged potato plants without exposure to potato psyllids (uninfested controls) did not show any ZC symptom in both foliage and in harvested tubers. Foliage damage and ZC expression were most severe in the potato plants that were exposed to potato psyllids 4 weeks after germination compared to plants infested at later growth stages. Tubers from potato psyllid-infested plants had significantly higher levels of reducing sugars (glucose) and lower levels of starch than those in healthy plants, indicating that potato psyllid infestation interfered with carbohydrate metabolism in either leaves or tubers, resulting in ZC expression.

BACKGROUND: Among plant nutrients, potassium (K) has the strongest influence on crop quality parameters that determine consumer preference. However, soil and plant factors often limit adequate soil K uptake to satisfy quality requirements during fruit development stages. The objectives of this multiyear field study with muskmelon were to determine if this apparent K deficiency and the associated fruit quality limitations can be alleviated by supplementing soil-derived K with foliar K nutrition, and whether differences exist among potential foliar K salts. RESULTS: Foliar K treatments increased tissue K concentrations, fruit sugars and bioactive compounds (ascorbic acid and β-carotene) by 19%, 21% and 15%, respectively, even though soil K levels were high, indicating that soil K alone was inadequate to improve these quality traits. All the K salts evaluated increased tissue K and fruit quality traits; however, no clear trends in the relative magnitudes of these enhancements were apparent among K sources, except for KNO3 which consistently resulted in non-significant effects. CONCLUSIONS: These results demonstrate that late-season foliar K feeding can improve fruit quality of muskmelons grown on calcareous soils. The data also reveal differences among K salts and suggest a reassessment of K management strategies aimed at improving quality. Copyright © 2009 Society of Chemical Industry

This study was conducted to characterize shortday onions of 3 pungency levels with regard to the composition of flavor related compounds. A total of 9 onion breeding lines/cultivars were selected, per each of low, medium, and high pungency level, with pyruvic acid contents of 1.9 to 2.8, 4.8 to 5.4, and 7.2 to 8.3 micromoles/mL, respectively. The contents of flavor precursors (S-1-propenyl-L-cysteine sulfoxide [1-PeCSO] and S-methyl-L-cysteine-sulfoxide [MCSO]), free amino acids, free sugars, soluble solids (SSC), and total sulfur (S) in onion bulbs were measured. The flavor precursor contents ranged from 0.03 to 0.16 mg/g fresh weight (FW) for MCSO, 0.07 to 0.65 mg for 1-PeCSO, and 0.12 to 0.77 mg in total, and precursor contents increased with the pungency levels. Onions of different pungency levels did not differ in the contents of individual or total free amino acids, and the most abundant amino acids were glutamine and arginine. The total sugar contents ranged from 50 to 75 mg/g FW, and total S contents (3.5 to 5.1 mg/g dry weight) were not correlated with the pungency levels. However, pungency levels were correlated inversely with bulb weight and positively with SSC, presumably by the effect of dilution. This study indicates that onion pungency is primarily determined by the content of flavor precursor compounds and not by total S, total sugars, or individual/total free amino acids in shortday bulbs.

Netted muskmelon (Cucumis melo L. (Reticulatus Group)) fruit quality (ascor- bic acid, `-carotene, total free sugars, and soluble solids concentration (SSC)) is directly related to plant potassium (K) concentration during fruit growth and maturation. During reproductive development, soil K fertilization alone is often inadequate due to poor root uptake and competitive uptake inhibition from calcium and magnesium. Foliar applica- tions of glycine-complexed K during muskmelon fruit development has been shown to improve fruit quality, however, the influence of organic-complexed K vs. an inorganic salt form has not been determined. This glasshouse study investigated the effects of two K sources: a glycine-complexed K (potassium metalosate, KM) and potassium chloride (KCl) (both containing 800 mg K/L) with or without a non-ionic surfactant (Silwet L- 77) on melon quality. Orange-flesh muskmelon 'Cruiser' was grown in a glasshouse and fertilized throughout the study with soil-applied N-P-K fertilizer. Starting at 3 to 5 d after fruit set, and up to 3 to 5 d before fruit maturity at full slip, entire plants were sprayed weekly, including the fruit, with KM or KCl with or without a surfactant. Fruit from plants receiving supplemental foliar K had significantly higher K concentrations in the edible middle mesocarp fruit tissue compared to control untreated fruit. Fruit from treated plants were also firmer, both externally and internally, than those from non-treated control plants. Increased fruit tissue firmness was accompanied by higher tissue pressure potentials of K treated plants vs. control. In general, K treated fruit had significantly higher SSC, total sugars, total ascorbic acid, and `-carotene than control fruit. Fall-grown fruit generally had higher SSC, total sugars, total ascorbic acid and `- carotene concentrations than spring-grown fruit regardless of K treatment. The effects of surfactant were not consistent but in general, addition of a surfactant tended to affect higher SSC and `-carotene concentrations. With the exception of nitrogen, potassium is required by plants in much greater amounts than all the other soil-supplied nutrients (Tis- dale et al., 1985). Adequate supply of fertilizer potassium is necessary for sustainable crop production. Plants obtain K primarily from the soil in the form of K + which is also strongly adsorbed by soil components, particularly clay particles and is, therefore, not readily mobile in most soils (Brady, 1984; Tisdale, et al., 1985). Potassium uptake by plants from the soil solution is regulated by several factors includ- ing texture, moisture conditions, pH, aeration, and temperature (Mengel and Kirkby, 1980; Tisdale et al., 1985). Clay soils can adsorb and hold more K and exchange it with the soil solution for plant uptake than sandy soils. Both calcium and magnesium compete with K for root uptake, hence plants grown in these soils often exhibit K deficiencies even though soil analyses indicate adequate K. Furthermore

Average global surface temperatures are predicted to rise due to increasing atmospheric CO2 and other greenhouse gases. Attempts to predict plant response to CO2 must take into account possible temperature effects on phenology and reproductive sink capacity for carbohydrates. In this study, we investigated the effects of atmospheric CO2 partial pressure (35 Pa ambient CO2 (aCO2) vs. 70 Pa elevated CO2 (eCO2)) and temperature (26/15 vs. 35/21 °C day/night) on short- and long-term net CO2 assimilation (An) and growth of red kidney bean (Phaseolus vulgaris). Dur- ing early vegetative development (14-31 days after planting (DAP)), An, and relative growth rate (RGR) at eCO2 were signifi cantly greater at the supra-optimum (35/21 °C) than at the optimum (26/15 °C) temperature. At 24 DAP, the CO2 stimulation of An by eCO2 was 49% and 89% at optimum and supra-optimum temperature, respectively, and growth enhancement was 48% and 72% relative to plants grown at aCO2. This high temperature-induced growth enhancement was accompanied by an up-regulation of An of eCO2-grown plants. In contrast, during later reproductive stages (31-68 DAP) the eCO2 stimulation of An was signifi cantly less at the supra-optimum than at optimum temperature. This was associated with reduced seed set, greater leaf carbohydrate accumulation, and down-regulation of An at the higher temperature. At fi nal harvest (68 DAP), the eCO2 stimulation of total dry weight was 31% and 14% at optimum and supra-optimum temperature respectively, and eCO2 stimulation of seed dry weight was 39% and -18% at optimum and supra-optimum temperature, respectively. These data indicate substantial shifts in the response to eCO2 during different phenological stages, and suggest that impaired reproductive development at high temperature could reduce the potential for CO2 stimulation of photosynthesis and productivity in bean and possibly other heat-sensitive species. One of the outcomes of the sustained emission of carbon dioxide and other radiatively active "greenhouse" gases into the atmosphere is an increase in mean global surface temperatures of ≈2-5 °C (Intergovernmental Panel on Climate Change, 2001; Stokstad, 2004). An increase in the frequency of extreme weather events such as periods of high temperature is also possible (Rosen- zwieg and Hillel, 1998). Such unfavorable environmental factors could limit crop productivity in a future CO2-enriched world. A better understanding of high-temperature stress effects on the response of plants to elevated CO2 (eCO2) will be important to predict the environmental and economic impacts of a continued increase in greenhouse gases. In general, the eCO2 stimulation of net CO2 assimilation (An) in C3 plants tends to increase as temperatures rise in the non-stress range of 15-30 °C (Long, 1991; Sage et al., 1995; Wilks et al., 1995). However, when temperatures are high enough to impair reproductive development, the eCO2 stimulation of An may not translate into higher crop yields due to reduced seed or fruit set. Also, a reduced reproductive sink capacity could exacerbate

Muskmelon [Cucumis melo L. (Reticulatus Group)] fruit sugar content is directly related to potassium (K)-mediated phloem transport of sucrose into the fruit. However, during fruit growth and maturation, soil fertilization alone is often inadequate (due to poor root uptake and competitive uptake inhibition from calcium and magnesium) to satisfy the numerous K-dependent processes, such as photosynthesis, phloem transport, and fruit growth. Experiments were conducted during Spring 2003 and 2004 to determine if supplemental foliar K applications during the fruit growth and maturation period would alleviate this apparent inadequate K availability in orange-flesh muskmelon `Cruiser'. Plants were grown in a greenhouse and fertilized throughout the study with a soil-applied N-P-K fertilizer. Flowers were hand pollinated and only one fruit per plant was allowed to develop. Starting at 3 to 5 days after fruit set, and up to 3 to 5 days prior to fruit maturity (full slip), entire plants, including the fruit, were sprayed with a glycine amino acid-complexed potassium (potassium metalosate, 24% K) solution, diluted to 4.0 mL·L-1. Three sets of plants were sprayed either weekly (once per week), biweekly (once every 2 weeks) or not sprayed (control). Fruit from plants receiving supplemental foliar K matured on average 2 days earlier than those from control plants. In general, there were no differences in fruit maturity or quality aspects between the weekly and biweekly treatments except for fruit sugar and beta-carotene concentrations, which were significantly higher in the weekly compared to the biweekly or control treatments. Supplemental foliar K applications also resulted in significantly firmer fruit with higher K, soluble solids, total sugars, ascorbic acid (vitamin C) and beta-carotene concentrations than fruit from control plants. These results demonstrate that carefully timed foliar K nutrition can alleviate the developmentally induced K deficiency effects on fruit quality and marketability.

Correlations between extractable leaf chlorophyll (Chl) concentration and portable, nondestructive leaf "greenness" meter readings imply that such estimates can be used as surrogate measurements of leaf nitrogen (N) status. However, few studies have actually found a direct relationship between Chl meter readings and leaf N. We evaluated the utility of two handheld transmittance-based Chl content meters (SPAD-502, Minolta Corp. and CCM-200, Opti- Sciences) and one refl ectance-based meter (Observer, Spectrum Technologies), in estimating Chl and N concentrations in intact leaves of several citrus cultivars. Total Chl determined analytically, correlated well with nondestructive Chl meter readings (r 2 : 0.72 to 0.97; P < 0.0001), but regression models differed among cultivars using the same meter and also among meters for a given cultivar. The relationships were generally more linear and stronger at low Chl con- centrations (

Effects of foliar sprays of a kaolin clay particle film (Surround WP) on leaf temperature (Tlf), net gas exchange, chlorophyll fluorescence and water relations of sun-exposed leaves on field-grown grapefruit trees (Citrus paradisi L.) were studied during Summer and Fall 2001. Trees were sprayed twice a week for 3 weeks with aqueous suspensions of kaolin (Surround) at 60 g·L-1. Physiological effects of kaolin application were most prominent around midday on warm sunny days than in mornings, evenings or cloudy days. Kaolin sprays increased leaf whiteness (62%), reduced midday leaf temperature (Tlf; ≈3 °C) and leaf to air vapor pressure differences (VPD; ≈20%) compared to water-sprayed control leaves. Midday reductions in Tlf and VPD were accompanied by increased stomatal conductance (gs) and net CO2 assimilation rates (ACO2) of kaolin sprayed leaves, suggesting that gs might have limited ACO2 in water-sprayed control leaves. Midday photoinhibition of photosynthesis was 30% lower in kaolin-sprayed leaves than in control leaves. Midday water use efficiency (WUE) of kaolin-sprayed leaves was 25% higher than that of control leaves. However, leaf transpiration and whole-tree water use were not affected by kaolin film sprays. Increased WUE was therefore, due to higher ACO2. Leaf intercellular CO2 partial pressures (Ci) were similar in control and kaolin-sprayed leaves indicating that stomatal conductance was not the major cause of reduced ACO2. These results demonstrate that kaolin sprays could potentially increase grapefruit leaf carbon uptake efficiency under high radiation and temperature stress.

Long-term exposure of plants to elevated CO2 often leads to downward photosynthetic acclimation. Nitrogen (N) deficiency could potentially exacerbate this response by reducing growth rate and the sink for photosynthates, but this has not always been observed. Experimentally, the interpretation of N effects on CO2 responses can be confounded by increasing severity of tissue N deficiency over time when N supply is not adjusted as demand increases. In this study, N supply ranged from sub- to supra-optimal (20–540 kgN ha–l equivalent), and relatively stable levels of tissue N concentration were obtained in all treatments by varying twice-weekly application rates in proportion to plant growth. The effects of N on photosynthesis and growth of beans (Phaseolus vulgaris L.) raised at ambient (35 Pa) and three elevated (70, 105, 140 Pa) CO2 partial pressures (pCO2) were evaluated. Averaging across N treatments, leaf total non-structural carbohydrates (TNC) were 2.5- to 3-fold higher and leaf N concentrations were 31–35% lower at elevated compared to ambient pCO2. Light-saturated net CO2 assimilation rates measured at growth pCO2 (Asatg) were significantly higher (26–40% depending on N supply) in plants grown at elevated compared to ambient pCO2. When measured at a common pCO2 of 35 Pa, the Asat of plants grown at elevated CO2 was 15–29% less than that of plants grown at 35 Pa, indicative of downward photosynthetic acclimation. The magnitude of downward photosynthetic acclimation to elevated CO2 was greater in plants grown at high (180 and 540 kgN ha–l) compared to low (20 and 60 kgN ha–l) N supply, and this was associated with a higher Asat at growth pCO2, higher leaf area ratio (leaf area/total biomass), and higher TNC in leaves of high-N plants. Our results indicate that the effect of N on acclimation to CO2 will depend on the balance between supply and demand for N during the growing period, and the effect this has on biomass allocation and source-sink C balance at the whole-plant level.

We investigated effects of salinity on the growth and net gas exchange of CO2 and water vapour in leaves of 2-year-old ‘Sunburst’ mandarin [(Citrus reticulata Blanco)×(Citrus paradisi Macf.×C. reticulata)] trees grafted on either Cleopatra mandarin (C. reticulata) or Carrizo citrange (Citrus sinensis L. Osb.×Poncirus trifoliata L.) rootstocks. Trees were grown in a greenhouse and watered with a complete nutrient solution containing 0, 30, 60 or 90 mM NaCl. After 6 weeks of treatment, tree growth, net gas exchange of leaves, leaf chlorophyll and mineral nutrient concentration were measured. Salinity decreased growth and net gas exchange of leaves on all trees. Cleopatra roots accumulated higher concentrations of Cl− and Na+ than Carrizo roots but ‘Sunburst’ leaves on Cleopatra accumulated less Cl− and Na+ and had higher CO2 exchange rates than those on Carrizo. This corresponded to higher concentrations of leaf N and chlorophyll in leaves of trees on Cleopatra than on Carrizo. Salinity increased N and decreased K+ contents in roots of both rootstocks. Salinity increased N and decreased K+ concentrations in leaves of trees on Cleopatra but not in trees on Carrizo. Salinity also increased Ca2+ concentration and reduced Mg2+ in leaves on Cleopatra. The lower Cl− and Na+ concentration in leaves of ‘Sunburst’ grafted on Cleopatra than on Carrizo, suggests that the salinity tolerance of Cleopatra is associated with ion sequestration in roots with less transport to leaves.

Although urea can be an effective adjuvant to foliar sprays, we examined effects of additional surfactants on urea penetration through leaf cuticles along with the effect of urea with and without surfactants on net gas exchange of leaves of `Marsh' grapefruit (Citrus paradisi Macf.) trees budded to Carrizo citrange (C. sinensis L. Osbeck × Poncirus trifoliata L. Raf.) rootstock. Various combinations of urea, a nonionic surfactant (X-77), and an organosilicone surfactant (L-77), were applied to grapefruit leaves and also to isolated adaxial cuticles. When compared to X-77, L-77 exhibited superior surfactant features with smaller contact angles of droplets deposited on a teflon slide. Both L-77 and X-77 initially increased penetration rate of urea through cuticles, but the effect of X-77 was sustained for a longer period of time. The total amount of urea which penetrated within a 4-day period, however, was similar after addition of either surfactant. Solutions of either urea, urea + L-77, urea + X-77, or L-77 alone decreased net assimilation of CO2 (ACO2) for 4 to 24 hours after spraying onto grapefruit leaves. A solution of X-77 alone had no effect on ACO2 over the 4-day period. Although reductions in ACO2 were similar following sprays of urea formulated with two different surfactants, the underlying mechanisms may not have been the same. For the urea + X-77 treatment, X-77 increased the inhibitory effects of urea on ACO2 indirectly by increasing penetration of urea into leaves. For the urea + L-77 formulation, effects of L-77 on ACO2 were 2-fold, direct by inhibiting ACO2 and indirect by increasing urea penetration. One hour after application, scanning electron microscopy (SEM) of leaf surfaces treated with X-77 revealed that they were heavily coated with the residue of the surfactant, whereas leaves treated with L-77 looked similar to nontreated leaves with no apparent residues on their surfaces. The amount of X-77 residue on the leaves was lower 24 hours after application than after 1 hour as observed by SEM.

Comparison of spinach (Spinacia oleracea L.) cultivars Lazio and Samish grown during the summer solstice in the subarctic versus the winter solstice in the subtropics provided insight into interactions between production environment (light intensity), cultivar, and leaf age/maturity/position affecting bionutrient concentrations of vitamins (C, E, folate, K1, provitamin A), lutein, phenolics, and antioxidants. Growing spinach during the winter solstice in the subtropics resulted in increased leaf dry matter %, oxidized (dehydro) ascorbic acid (AsA), α- and γ-tocopherol, and total phenols but lower reduced (free) AsA, α-carotene, folate, and antioxidant capacity compared to summer solstice-grown spinach in the subarctic. Both cultivars had similar bionutrients, except for higher dehydroAsA, and lower α- and γ-tocopherol in 'Samish' compared to 'Lazio'. For most bionutrients measured, there was a linear, and sometimes quadratic, increase in concentrations from bottom to top canopy leaves. However, total phenolics and antioxidant capacity increased basipetally. The current study has thus demonstrated that dehydroAsA, α-tocopherol, and γ-tocopherol were substantially lower in subarctic compared to subtropical-grown spinach, whereas the opposite relationship was found for antioxidant capacity, α-carotene, and folates (vitamin B9). The observations are consistent with previously reported isolated effects of growth environment on bionutrient status of crops. The current results clearly highlight the effect of production environment (predominantly radiation capture), interacting with genetics and plant phenology to alter the bionutrient status of crops. While reflecting the effects of changing growing conditions, these results also indicate potential alterations in the nutritive value of foods with anticipated shifts in global climatic conditions.

The effects of CO2 enrichment on root proliferation of loblolly pine (Pinus taeda L.) and sweetgum (Liquidambar styracijlua L.) seedlings were studied under varied water and nitrogen (N) regimes and in competitive interaction. Seedlings of each species were grown from seed as monocultures or as 50:50 pine-sweetgum mixtures in 22-L pots filled with forest soil. Seedlings were exposed to either ambient (400 ppm) or CO2-enriched (ambient plus 400 ppm) air for 32 weeks in continuously stirred tank reactors. Detailed sampling of very fine roots (>0.5 mm diam.) showed a general increase (up to 2-fold) in root length density (RLD, cm · m-3 with elevated CO2; however, the effects of CO2 on RLD differed according to species, culture type, water, and N availability. In monoculture, low water with low N conditions produced the largest RLD responses to elevated CO2: 75% increase for sweetgum and 31% increase for pine. In mixed culture, by contrast, the largest RLD responses to CO2 were observed under high water, high N regimes: pine showed a 110% increase and sweetgum a 96% increase. The total RLD of the standing crop in mixture under elevated CO2, high water, and high N was 2.6 cm · m-3 compared with 1.6 cm · m-3 in ambient CO2, with sweetgum accounting for >75% of the total RLD in both cases. These findings suggest that resource-rich rather than resource-poor soil environments could be th.e circumstances under which belowground interference from sweetgum would intensify in pine-sweetgum mixtures with rising atmospheric CO2.

Concentrations of grapefruit (cv. 'Rio Red'; Citrus paradisi Macf.) bioactives grown under organic and conventional production systems were evaluated after storage at various temperatures. The first experiment was conducted in November 2008 and the second experiment was conducted in February 2011 using commercial production, processing, and packing procedures. The harvested grapefruits were stored at 23 °C (room temperature) or 9 °C for 4 weeks and analyzed for vitamin C, limonoids, and carotenoids at the end of each week using HPLC. Vitamin C levels were higher in organically grown grapefruits (41.8 mg/100 g) compared to conventionally grown grapefruits (39.2 mg/100 g) at 0 days after harvest in the first experiment. However, production system did not significantly affect vitamin C levels in the second experiment. During storage at room temperature, vitamin C degradation losses ranged from 0.5 to 7% for organically produced grapefruits and from 3 to 18% for conventional grapefruits in both experiments. In the first experiment at harvest, organically produced grapefruits had 77% higher (p ≤ 0.05) nomilin than conventionally produced grapefruits, whereas grapefruits grown under the conventional production system had 2-fold higher lycopene levels compared to organic grapefruits. In the second experiment, both β-carotene and lycopene levels were significantly (p ≤ 0.05) higher in conventionally produced grapefruits than in organic grapefruits. Overall, conventional production significantly increased grapefruit carotenoid levels in both experiments. In general, storage temperature (room temperature and 9 °C) had minimal effects on vitamin C degradation but significant effects on the degradation of carotenoids in the first experiment.

Peppers (Capsicum spp.) are a rich source of diverse bioactive compounds with potential health-promoting properties. This study investigated the extraction efficiency of five solvents on antioxidant activities from cayenne (CA408 and Mesilla), jalapeno (Ixtapa) and serrano (Tuxtlas) pepper cultivars. Freeze-dried peppers were extracted using a Soxhlet extractor with five solvents: hexane, ethyl acetate, acetone, methanol, and methanol:water (80:20). The levels of specific bioactive compounds (phenolics, capsaicinoids, carotenoids and flavonoids) were determined by HPLC and antioxidant activities were assayed by three methods. For all pepper cultivars tested, hexane extracts had the highest levels of capsaicinoids and carotenoids, but methanol extracts had the maximum levels of flavonoids. Hexane extracts showed higher 2,2-diphenyl-1-pricrylhydrozyl (DPPH) radical-scavenging activity and higher reducing power, and acetone extracts (from Mesilla pepper) had a high reducing power. All pepper extracts, except hexane, were effective in preventing deoxyribose degradation, and the inhibition was increased by high concentrations of extracts. The results of the present study indicated that, among the different measures of antioxidant activity, DPPH radical-scavenging activity was strongly correlated with total bioactive compounds (capsaicinoids, carotenoids, flavonoids and total phenolics) in pepper cultivars.

Among the many plant mineral nutrients, potassium (K) stands out as a cation having the strongest influence on quality attributes that determine fruit marketability, consumer preference, and the concentration of critically important human-health associated phytonutrients. However, many plant, soil, and environmental factors often limit adequate uptake of K from the soil in sufficient amounts to satisfy fruit K requirements during development to optimize the aforementioned quality attributes. The objectives of this review are 1) to summarize published study abstracts on the effects of soil and/or foliar K fertilization as well as diverse K forms, on fruit phytonutrient concentrations; and 2) to illustrate the important role of K forms on fruit quality with a case study of Cucumis melo L (muskmelon) fruit produced with optimal soil applied K . The muskmelon studies will compare commercial sources (forms) of K applied to examine seasonal effects (spring vs. autumn) and the number of foliar K applications during fruit development on fruit marketability (maturity, yield, firmness, soluble solids, sugars, relative sweetness), consumer preference attributes (sugar content, sweetness, texture), and phytochemical concentrations (K, ascorbic acid, and β-carotene concentrations). Numerous studies have consistently demonstrated that specific K fertilizer forms, in combination with specific application regimes, can improve fruit quality attributes. Potassium fertilizer forms in order of effectiveness (Glycine (Gly)-complexed K = K2SO4 ≥ KCl > no K > KNO3) when applied wet (foliar or hydroponic) vs. dry (soil) were generally superior in improving fruit marketability attributes, along with many human-health nutrients. The muskmelon case study demonstrated that two K forms: Gly-complexed K and K2SO4, combined with a silicone-based surfactant, applied weekly, as a foliar spray, during fruit development, from both autumn and spring-grown plants, had the greatest impact on improving fruit marketability attributes (maturity, yield, firmness, and sugars), as well as fruit quality attributes (human-health bioactive compounds K, ascorbic acid, and β-carotene). Among several foliar applied K salts studied under field conditions so far, salts with relatively low salt indices appeared to have the greatest impacts on fruit quality when applied during the mid- to late-season fruit development periods.