Glucobrassicin Concentration Research Articles

Functional support vector machine.

Linear and generalized linear scalar-on-function modeling have been commonly used to understand the relationship between a scalar response variable (e.g. continuous, binary outcomes) and functional predictors. Such techniques are sensitive to model misspecification when the relationship between the response variable and the functional predictors is complex. On the other hand, support vector machines (SVMs) are among the most robust prediction models but do not take account of the high correlations between repeated measurements and cannot be used for irregular data. In this work, we propose a novel method to integrate functional principal component analysis with SVM techniques for classification and regression to account for the continuous nature of functional data and the nonlinear relationship between the scalar response variable and the functional predictors. We demonstrate the performance of our method through extensive simulation experiments and two real data applications: the classification of alcoholics using electroencephalography signals and the prediction of glucobrassicin concentration using near-infrared reflectance spectroscopy. Our methods especially have more advantages when the measurement errors in functional predictors are relatively large.

Using Near-infrared reflectance spectroscopy (NIRS) to predict glucobrassicin concentrations in cabbage and brussels sprout leaf tissue

BackgroundGlucobrassicin (GBS) and its hydrolysis product indole-3-carbinol are important nutritional constituents implicated in cancer chemoprevention. Dietary consumption of vegetables sources of GBS, such as cabbage and Brussels sprouts, is linked to tumor suppression, carcinogen excretion, and cancer-risk reduction. High-performance liquid-chromatography (HPLC) is the current standard GBS identification method, and quantification is based on UV-light absorption in comparison to known standards or via mass spectrometry. These analytical techniques require expensive equipment, trained laboratory personnel, hazardous chemicals, and they are labor intensive. A rapid, nondestructive, inexpensive quantification method is needed to accelerate the adoption of GBS-enhancing production systems. Such an analytical method would allow producers to quantify the quality of their products and give plant breeders a high-throughput phenotyping tool to increase the scale of their breeding programs for high GBS-accumulating varieties. Near-infrared reflectance spectroscopy (NIRS) paired with partial least squares regression (PLSR) could be a useful tool to develop such a method.ResultsHere we demonstrate that GBS concentrations of freeze-dried tissue from a wide variety of cabbage and Brussels sprouts can be predicted using partial least squares regression from NIRS data generated from wavelengths between 950 and 1650 nm. Cross-validation models had R2 = 0.75 with RPD = 2.3 for predicting µmol GBS·100 g−1 fresh weight and R2 = 0.80 with RPD = 2.4 for predicting µmol GBS·g−1 dry weight. Inspections of equation loadings suggest the molecular associations used in modeling may be due to first overtones from O–H stretching and/or N–H stretching of amines.ConclusionsA calibration model suitable for screening GBS concentration of freeze-dried leaf tissue using NIRS-generated data paired with PLSR can be created for cabbage and Brussels sprouts. Optimal NIRS wavelength ranges for calibration remain an open question.

Abstract A41: Assessing the effect of glucobrassicin-rich Brussels sprouts on the metabolism of deuterated phenanthrene: Developing food-based chemoprevention of tobacco-related lung cancer

Abstract Introduction: Indole-3-carbinol (I3C) and 3,3-´diindolylmethane (DIM), derived from the glucosinolate glucobrassicin, are found in cruciferous vegetables. I3C and DIM possess a potent chemopreventive effect against the development of tobacco carcinogen-induced lung tumors in mice. Polycyclic aromatic hydrocarbons (PAH) are potent lung carcinogens present in high levels in tobacco smoke. An individual’s ability to metabolically activate and/or detoxify PAH may be related to lung cancer risk from smoking. We hypothesize that I3C administered by eating a rational dose of Brussels sprouts, defined in terms of glucobrassicin concentration, can decrease the metabolic activation and/or increase detoxification of PAH, represented by the noncarcinogenic PAH [D10]Phenanthrene ([D10]Phe). Use of deuterated phenanthrene eliminates confounding by environmental phenanthrene. Metabolic activation of [D10]Phe is represented by [D10]Phenanthrene tetraol ([D10]PheT), and detoxification is represented by [D10]phenanthrol. We are conducting a clinical trial to determine whether glucobrassicin-rich Brussels sprouts can favorably modify the metabolism of the [D10]Phe. Study Design: This is a single-arm clinical trial. The primary objective is to determine the effect of a 7-day course of Brussels sprout consumption on [D10]PheT. Secondary objectives include analysis of [D10]phenanthrol and the [D10]PheT:[D10]phenanthrol ratio. Exploratory objectives include determining the correlation between 24 h urinary DIM with the reduction in [D10]PheT, and determining the effect of Brussels sprout consumption on circulating immune cell composition and activity. Forty-eight generally healthy, adult current smokers and former smokers will be enrolled. Subjects are given 1 microgram of [D10]phe, and all urine is collected for 6 hours (h) afterwards to quantify baseline levels of [D10]PheT and [D10]phenanthrol. Subjects then consume 200 micromol glucobrassicin in the form of raw Brussels sprouts (~200-300 g) once daily for 7 days. Urine is collected for 24 h after vegetable consumption on days 3 ± 1 and 6 of the feeding intervention for DIM quantification. On day 7 of the feeding intervention, a second dose of 1 microgram of [D10]phe is administered at the study center 60 minutes ± 10 minutes after vegetable consumption, followed by another 6 h urine collection. [D10]pheT and [D10]phenanthrol levels are quantified using a validated tandem mass spectrometry assay. Pre- and post-[D10]PheT levels are compared using a paired t-test after log transformation. The results will also be analyzed by GSTT1 and GSTM1 genotyping. Results: Twelve subjects have completed the study. Baseline [D10]PheT levels ranged from 48.34 to 331.05 pmol/6 h. Day 7 [D10]PheT levels ranged from 26.57 to 333.35 pmol/6 h. Percent change from baseline to Day 7 [D10]PheT ranged from a 33% decrease to an 86.5% increase (mean +/- SE of 12.8 +/- 11.6%). Conclusions: The study is ongoing and more subjects are necessary to make a definitive conclusion. Citation Format: Naomi Fujioka, Michelle To, Bruce R. Lindgren, Vincent A. Fritz, Charles Rohwer, Dorothy Hatsukami, Stephen S. Hecht. Assessing the effect of glucobrassicin-rich Brussels sprouts on the metabolism of deuterated phenanthrene: Developing food-based chemoprevention of tobacco-related lung cancer [abstract]. In: Proceedings of the AACR Special Conference on Environmental Carcinogenesis: Potential Pathway to Cancer Prevention; 2019 Jun 22-24; Charlotte, NC. Philadelphia (PA): AACR; Can Prev Res 2020;13(7 Suppl): Abstract nr A41.

Influence of different types of modified atmosphere packaging films and storage time on quality and bioactive compounds in fresh-cut cauliflower

Abstract Minimal or fresh processing of cauliflower is becoming much more common than using the intact cauliflower in food service and retail markets as a convenience product. Therefore, the objective is to investigate the effect of different types of modified atmosphere packaging films and storage time on postharvest quality and bioactive compounds in fresh-cut cauliflower. Fresh-cut cauliflowers were packed in different films [Polypropylene (gas concentrations at equilibrium: (0.38%, O2, 28.53%, CO2), Peakfresh (19.4%O2 & 1.62% CO2), 20% fixed area of NatureFlex film + 80% Bi-axially Polypropylene (6.06%O2 & 11.43%CO2) and 40% fixed area of NatureFlex film + 60% Bi-axially Polypropylene (16.87% O2 & 5.87% CO2) and stored at 5 C and 85% RH for up to 12 days. Samples were withdrawn at 4 day intervals. The optimal colour retention, characteristic cauliflower odour, and overall acceptance was highest up to day 8 in a package with 20% fixed area of NatureFlex, which can be recommended for packaging of fresh-cut cauliflower. The Polypropylene packed samples showed the highest total phenol, flavonoid (quercetin), FRAP, ABTS+ activity on day 4. On day 8, retention of glucobrassicin, 4-methoxy glucobrassicin, 1-methoxy glucobrassicin concentrations showed the following order: Poplypropylene >20% fixed area of NatureFlex >40% fixed area of NatrueFlex.

Antibiotic properties of the glucosinolates of Brassica oleracea var. acephala similarly affect generalist and specialist larvae of two lepidopteran pests

Glucosinolates may deter generalist insect feeding as their toxicity causes fitness damage, whereas insects specialized in brassicaceous plants may circumvent the toxic effect. By using no-choice leaf tests, we investigated whether larval development time, body weight, mortality and feeding rate of the generalist Mamestra brassicae (Lepidoptera, Noctuidae) and the specialist Pieris rapae (Lepidoptera, Pieridae), were affected by six genotypes of Brassica oleracea var. acephala, selected for having high or low concentration of sinigrin, glucoiberin (aliphatics) and glucobrassicin (indole). Two phenological plant stages were used. On young plants, M. brassicae most consumed the high sinigrin and low glucoiberin genotypes. Larvae weighed more on the high sinigrin plants. Development time took longer on the low glucoiberin genotype. On mature plants, consumption rate decreased on the high glucoiberin genotype. Larval weight decreased on the high sinigrin, glucoiberin and glucobrassicin genotypes, and development time increased with high glucobrassicin concentration. Pupal weight and mortality rate increased on mature plants, irrespective of the genotype. Pieris rapae fed most on young plants with high sinigrin, and larval weight increased on the high glucoiberin genotype. Mortality increased with low glucoiberin and low glucobrassicin. On mature plants, larval weight decreased with high sinigrin and glucoiberin. The high glucoiberin genotype was the less consumed and also induced a longer development time. High content of aliphatic glucosinolates offered mature plants significant antibiosis defence against both the lepidopterans, whereas the indole glucosinolate was marginally effective. Young plants were more consumed and increased larval weight likely because glucosinolate concentration was still not optimal.

Variations in the most abundant types of glucosinolates found in the leaves of baby leaf rocket under typical commercial conditions

Changes in the concentration of the three most abundant glucosinolates were measured in the leaves of perennial wall rocket [Diplotaxis tenuifolia (L.) DC.], and annual garden rocket (Eruca sativa Mill.). HPLC-MS was used to identify glucoraphanin, 4-hydroxyglucobrassin and glucoerucin from perennial wall rocket, and glucoraphanin, glucobrassicin and 4-methoxyglucobrassicin from annual garden rocket. In separate experiments the responses of glucosinolates to harvest number, seasonal conditions, nitrogen supply and post-harvest storage conditions were measured. For perennial wall rocket, season influenced the concentration of glucoraphanin, which were highest for the spring [379 µg kg(-1) fresh weight (FW)] and summer (317 µg kg(-1) FW) plantings. The concentration of 4-hydroxyglucobrassin was higher in the leaves of first harvest crops. This response was due to this glucosinolate not being detected in the leaves of second harvest crops. Thus, the parent glucosinolate was altered between the first and second harvests in response to the abiotic stresses caused by harvesting. For annual garden rocket, there was an interaction between the harvest number and season for all glucosinolates measured. However, no clear response was observed between these factors. Higher concentrations of glucobrassicin and 4-methoxyglucobrassicin were measured for first harvest leaves when compared to the second harvest. This was due to the absence of detection of these glucosinolates in the leaves of second harvested plants; consequently higher total glucosinolate concentrations were measured for the first harvest winter (1224 µg kg(-1) FW) and summer (864 µg kg(-1) FW) crops. The concentrations of individual glucosinolates vary greatly over typical pre- and post-harvest commercial conditions. The absence of 4-hydroxyglucobrassin for perennial wall rocket, and glucobrassicin and 4-methoxyglucobrassicin for annual garden rocket between harvests, illustrates that abiotic stress from harvesting has the capacity to alter the types of glucosinolates in leaves. Concentrations do not generally decline during a typical storage period, indicating that the potential benefits of these compounds are not lost during post-harvest storage.

YIELD COMPONENTS AND GLUCOSINOLATE CONTENTS OF BROCCOLI CULTIVARS IN SUMMER-AUTUMN GROWING CYCLE

In recent decades, interest for functional food has been increased. Plant derived food is important source of various bioactive compounds. The biologically active components in Brassica vegetables are the breakdown products of glucosinolates which have anticarcinogenic properties. Broccoli is included as a highly nutritious vegetable due to its mineral and vitamin content, fibres and bioactive compounds which depend on genetic, abiotic and agronomic factors. As numerous broccoli hybrid cultivars are available in Croatia, research with aim to select promising hybrid broccoli cultivars with appropriate agronomic and chemical traits was carried out during summer-autumn growing period of 2007. The field trial involving 13 hybrid broccoli cultivars was laid out according to four- replication block design. During harvest period basic morphometric values of top inflorescence were determined. Cultivar 'Montop' had the highest mass, diameter and yield of top inflorescence (506 g, 15.5 cm and 1.5 kg m-2). 'Green Magic' and 'Lucky' belong to the same range with slightly lower values of the mentioned parameters (457 g, 15.4 cm, 1.5 kg m-2 and 447 g, 14.1 cm, 1.5 kg m- 2, respectively). In all analyzed cultivars prevailing glucosinolate were glucoraphanin and glucobrassicin. There are significant differences in glucosinolate concentrations among cultivars. 'Fiesta' had the highest glucoraphanin level, 3.52 μmol g-1 dry weight (dw). This was followed by 'Agassi' and 'Marathon', which also achieved high glucoraphanin concentrations (2.85 and 2.80 μmol g-1 dw). 'General' obtained the highest glucobrassicin concentration (9.5 μmol g-1 dw), significantly higher than the other cultivars. 'Marathon' reached the highest total glucosinolate concentration (15.45 μmol g-1 dw). Neither cultivar can stand out with the highest values of agronomic parameters and bioactive components at the same time. The results point out 'Marathon' as the cultivar with a considerable content of glucoraphanin, glucobrassicin and total glucosinolates (2.58, 7.32 and 15.45 μmol g-1 dw, respectively), and with satiable marketable top inflorescence yield (1.06 kg m-2).

Urinary 3,3′-Diindolylmethane: A Biomarker of Glucobrassicin Exposure and Indole-3-Carbinol Uptake in Humans

Brassica vegetable consumption may confer a protective effect against cancer, possibly attributable to their glucosinolates. Glucobrassicin is a predominant glucosinolate and is the precursor of indole-3-carbinol (I3C), a compound with anticancer effects. However, objective assessments of I3C uptake from Brassica vegetables have not been successful. We conducted a randomized, crossover trial to test whether 3,3'-diindolylmethane (DIM, a metabolite of I3C) excreted in the urine after consumption of raw Brassica vegetables with divergent glucobrassicin concentrations is a marker of I3C uptake from such foods. Twenty-five subjects were fed 50 g of either raw "Jade Cross" Brussels sprouts (high glucobrassicin concentration) or "Blue Dynasty" cabbage (low glucobrassicin concentration) once daily for 3 days. All urine was collected for 24 hours after vegetable consumption each day. After a washout period, subjects crossed over to the alternate vegetable. Urinary DIM was measured using a novel liquid chromatography-electrospray ionization-tandem mass spectrometry-selected reaction monitoring (LC-ESI-MS/MS-SRM) method with [(2)H2]DIM as internal standard. Urinary DIM was consistently and significantly higher after Brussels sprouts feeding than after cabbage feeding, as evidenced by an average difference of 8.73 pmol/mg creatinine (95% confidence interval, 5.36-12.10; P = 0.00002). We have successfully quantified urinary DIM after uptake of I3C from food, and demonstrated that differences in glucobrassicin exposure are reflected in urinary DIM levels. Our LC-ESI-MS/MS-SRM method and the results of our study indicate urinary DIM is a measure of I3C uptake from Brassica vegetables, a finding that can be utilized in prospective epidemiologic and chemoprevention studies.

Effects of plant hormones on main health-promoting compounds and antioxidant capacity of Chinese kale

The effects of methyl jasmonate (MeJA), Ethrel (ETH), 1-methylcyclopropene (1-MCP) and salicylic acid (SA) treatments on contents of glucosinolates, vitamin C, total phenolics, carotenoids and chlorophyll, as well as antioxidant capacities were investigated in Chinese kale. MeJA treatment induced significant increase in the concentrations of glucobrassicin, neoglucobrassicin and total indole gulcosinolates, while SA treatments led to predominant enhancement of 4-methoxyglucobrassicin and aliphatic glucosinolates. The total phenolic content and the antioxidant capacities were remarkably increased by all the hormone treatments. In addition, the effect of SA treatments varied with different handling methods. Spraying on the aboveground parts is a better SA treatment approach than root irrigation. These results demonstrated that plant hormones, especially the MeJA and SA, significantly increased the contents of main health-promoting compounds, and enhanced the antioxidant capacities of Chinese kale.

Interactive effects of phosphorus supply and light intensity on glucosinolates in pakchoi (Brassica campestris L. ssp. chinensis var. communis)

The influences of phosphorus (P) supply levels (1.00 and 0.01 mM) and different light intensities (normal and 60% shading) on plant growth and glucosinolate (GS) concentrations were investigated in pakchoi (Brassica campestris L. ssp. chinesis (L.) Makino var. communis Tsen et Lee) plants grown in nutrient solution. Low light intensity significantly decreased the shoot and root growth, particularly under P sufficiency. P deficiency significantly decreased the shoot growth under normal light intensity, but did not significantly affect the root growth irrespective of the light intensity. The root/shoot ratio was increased by P deficiency and high light intensity. P deficiency largely increased the concentration of total GSs under normal light intensity by 164%, but this effect was not significant under low light intensity. However, the effects of P supply level and light intensity on seven individual GSs and three classes of GSs (aliphatic, aromatic and indolyl GSs) were quite different. The concentrations of gluconapin, glucobrassicanapin, glucobrassicin, neoglucobrassicin, 4-methoxyglucobrassicin and gluconasturtiin were increased by P deficiency, especially under normal light intensity resulting in increases of 122%, 497%, 352%, 115% and 225%, respectively. Low light intensity decreased the concentrations of gluconapin, glucobrassicanapin, glucobrassicin and neoglucobrassicin under P deficiency condition, and increased the concentrations of glucobrassicin and 4-methoxyglucobrassicin and neoglucobrassicin under P sufficiency condition. The ratios of aliphatic, aromatic and indolyl GSs to total GSs were not significantly affected by P supply level under low light intensity. However, under normal light intensity, P deficiency increased the ratio of aliphatic GSs to total GSs from 58% to 67%, at the expense of aromatic ones, and did not affect the ratio of indolyl GSs to total GSs. Altered concentrations of free amino acids (GS precursors) could not be related to changes of individual GSs. The concentration of sulfur in pakchoi shoots was not significantly affected by different P levels and light intensities. The results indicate a role of P and light, and their interaction, on the concentrations and profiles of GSs in the shoots of pakchoi plants. However, the physiological and molecular mechanisms underlying this response await further investigation.

Cabbage Yield and Glucosinolate Concentrations as Affected by Nitrogen and Sulfur Fertility

Glucosinolates are a class of nitrogen (N) and sulfur (S) containing compounds shown to have cancer-preventing properties in animal models and widely found in cruciferous plants. The overall objective of this study was to determine whether N and S fertility affects glucosinolate concentrations in cabbage (Brassica oleracea L. Capitata group). Field studies on a sandy soil low in available N and S were conducted over a 2-year period with both green (`Grand Slam') and red (`Vorox') cabbage cultivars. Treatments evaluated each year were the interactive effects of N (125 and 250 kg·ha–1) and S (0, and 110 kg·ha–1) fertilizer application. Yield of both cabbage cultivars increased with increasing N and S in the second year of the study, but not in the first. Tissue N concentrations in heads at harvest increased with N application and tissue S concentrations increased with S application. When S was not applied, tissue S decreased significantly as N rate increased, while N rate had no effect on tissue S concentrations when S was applied. The dominant glucosinolate detected in both cabbage cultivars was glucobrassicin, with indole forms accounting for about 80% of the total glucosinolates regardless of treatment. Tissue N was negatively correlated and tissue S and S to N ratio were positively correlated with total glucosinolate concentration, although all correlations were generally weak (r2 < 0.5). Total glucosinolates and glucobrassicin concentrations were maximized in both cultivars at the low N and high S application rates. Except for sinigrin in one of the 2 years, all glucosinolates detected were higher in Vorox than in `Grand Slam'. Based on these results, glucosinolates in cabbage can be manipulated by cultural management practices as well as genetics.

Correlation of Glucosinolate Content to Myrosinase Activity in Horseradish (Armoracia rusticana)

Fully developed horseradish (Armoracia rusticana Gaertn., Mey., & Scherb.) roots from 27 accessions and leaves from a subset of 9 accessions were evaluated for glucosinolates and myrosinase enzyme activity. Eight different glucosinolates were detected (based on HPLC retention times as desulfoglucosinolates) in both root and leaf tissues. The sum of these glucosinolates, referred to as total, ranged from 2 to 296 micromol g(-1) of dry weight (DW) in both tissues. Four glucosinolates (sinigrin, glucobrassicin, neoglucobrassicin, and gluconasturtiin) were detected in major quantities. In fully developed roots, sinigrin concentration represented approximately 83%, gluconasturtiin approximately 11%, and glucobrassicin approximately 1% of the total glucosinolates. Approximately the same proportions of individual glucosinolates appeared in fully developed leaves, except that glucobrassicin was substituted by neoglucobrassicin and gluconasturtiin concentration was significantly lower (<1%). At least four other glucosinolates were detected in very small quantities (<1%) in both roots and leaves. Myrosinase (beta-thioglucoside glucohydrolase, EC 3.2.3.1) is the enzyme responsible for the hydrolysis of the parent glucosinolates into biologically active products. Very little is known about myrosinase activity and the correlation of its activity to total and individual glucosinolates in plant tissues. Significant differences in myrosinase activity were detected between the roots and leaves, ranging from 1.2 to 57.1 units g(-1) of DW. Data showed no correlation between myrosinase activity and total and/or individual glucosinolates in the roots. However, in the leaves, significant correlations were found between myrosinase activity and total glucosinolates (0.78 at P = 0.01) and between myrosinase activity and sinigrin (0.80 at P = 0.01). Glucosinolates content and myrosinase activity were also correlated in young and fully developed roots and leaves and during tissue crushing. Glucobrassicin concentration in the roots and neoglucobrassicin concentration in the leaves were significantly higher in young than in fully developed tissue. Crushing of the tissue resulted in rapid hydrolysis of sinigrin and glucobrassicin, as expected, from the presence of myrosinase. Likewise, myrosinase activity declined rapidly after crushing, perhaps due to inactivation by the reaction products and/or the depletion of its substrates.

Is induction response negatively correlated with constitutive resistance in black mustard?

Black mustard, Brassica nigra, is highly variable in both constitutive resistance and induction response following damage by herbivores. A focal population from Ithaca, New York, was used to test the following two predictions of optimal defense theory: (1) that allocation to resistance will reduce plant performance in the absence of herbivores; and (2) that induction response will be negatively correlated with constitutive resistance. The experiment consisted of a half-sib mating design with 47 paternal families and four dams per sire, fully crossed with a damage treatment consisting of 25% leaf removal by the cabbage white butterfly, Pieris rapae, when plants had four leaves. Leaf trichome density, sinigrin concentration, and glucobrassicin concentration were 38%, 19%, and 16% higher, respectively, for the seventh leaf of damaged plants. Paternal families did not vary significantly in their induction response. Narrow-sense heritabilities were h(S)(2) = 0.51, 0.76, and 0.50 for constitutive leaf trichome density, sinigrin concentration, and glucobrassicin concentration, respectively. Positive genetic correlations were found between glucobrassicin concentration and days to first flower, suggesting a genetic cost of resistance. Induction responses were negatively correlated with constitutive allocation for leaf trichome density and sinigrin concentration. The results were therefore consistent with optimal defense theory, offering modest evidence for both predictions.

IS INDUCTION RESPONSE NEGATIVELY CORRELATED WITH CONSTITUTIVE RESISTANCE IN BLACK MUSTARD?

Black mustard, Brassica nigra, is highly variable in both constitutive resistance and induction response following damage by herbivores. A focal population from Ithaca, New York, was used to test the following two predictions of optimal defense theory: (1) that allocation to resistance will reduce plant performance in the absence of herbivores; and (2) that induction response will be negatively correlated with constitutive resistance. The experiment consisted of a half-sib mating design with 47 paternal families and four dams per sire, fully crossed with a damage treatment consisting of 25% leaf removal by the cabbage white butterfly, Pieris rapae, when plants had four leaves. Leaf trichome density, sinigrin concentration, and glucobrassicin concentration were 38%, 19%, and 16% higher, respectively, for the seventh leaf of damaged plants. Paternal families did not vary significantly in their induction response. Narrow-sense heritabilities were h2s = 0.51, 0.76, and 0.50 for constitutive leaf trichome density, sinigrin concentration, and glucobrassicin concentration, respectively. Positive genetic correlations were found between glucobrassicin concentration and days to first flower, suggesting a genetic cost of resistance. Induction responses were negatively correlated with constitutive allocation for leaf trichome density and sinigrin concentration. The results were therefore consistent with optimal defense theory, offering modest evidence for both predictions.

Auxin Activity of Glucobrassicin

AbstractThe indole‐glucosinolate, glucobrassicin, which is found in large amounts in members of the genus Brassica, was subjected to tests in the standard Avena curvature bioassay. Both the tetramethylammonium salt of glucobrassicin and the non‐crystallizted material induced curvature at a concentration of 5 × l0−4M. The curvature from the salt was, however, only half of that induced by the acid form.Bioassays of chromatograms of fresh methanolic extracts of savoy cabbage indicated the presence of indole‐3‐acetic acid as well as indole‐3‐acetonitrile in small amounts along with large amounts of glucobrassicin.Segments of green hypocotyl tissue of savoy cabbage respond with limited growth to high concentrations of glucobrassicin. Segments of etiolated hypocotyls or green epicotyls give no growth response to glucobrassicin.Pea stem segments which do not respond to indoleacetonitrile responded with similar growth to glucobrassicin and indoleacetic acid.Nitrilase activity was found in savoy hypocotyl and epicotyl tissue by chromatography of incubation media.The growth regulation in savoy cabbage in conjunction with data on the distribution of glucobrassicin in the plant, leads to the conclusion that glucobrassicin is a special, inactive storage and transport form of the active auxin in cabbage.