Correlations between morphological and biochemical characteristics of five common medicinal and aromatic plants : Data from Oliveira, I., Pinto, T., Faria, M., Bacelar, E., Ferreira, H., Correia, C., Gonçalves, B., 2017: Morphometrics and chemometrics as tools for medicinal and aromatic plants characterization. J. Appl. Bot. Food Qual. 90, 31-42. doi: 10.5073/JABFQ.2017.090.006
This data set includes all correlations found between morphological and biochemical characteristics of five common medicinal and aromatic plants (MAP’s) (Coriandrum sativum L. - coriander, Mentha spicata L. - spearmint, Ocimum basilicum L. - basil, Origanum vulgare L. - oregano and Petroselinum crispum Mill. - parsley). Pearson correlations were calculated using SPSS (Statistical Package for Social Sciences) version 19.0 software (IBM Corporation, New York, U.S.A.). Data includes morphological measurements (Leaf Area - AREA, Leaf length - LENG, Leaf perimeter - PERI, Leaf shape factor - SFACT, SLA - SLA, Leaf width - WIDT) as well as several biochemical characteristics (Carotenoid content - CARO, Chlorophyll a content - CLA, Chlorophyll b content - CLB, Chlorophyll a/b ratio – CLA/CLB, Total Chlorophyll content - CLT, Total Chlorophyll/Carotenoid ratio – CLT/CARO, Non-structural carbohydrate content - NSCA, Protein content - PROT, Soluble Sugar content - SSUG, Soluble Sugar/Stach ratio – SSUG/STAR, Starch content - STAR, TBARS - TBARS, Total phenolic content - TPHE, Water content - WCON), all expressed per leaf fresh weight (mg/g or nmol/g) or area (mg/dm2 or nmol/dm2), with the exception of water content, expressed as %. Biometric characterization - For the characterization of morphological parameters of the leaves of the studied plants, ten healthy and totally expanded mature leaves were selected, and the WinDIAS Leaf Area Meter System software (Delta-T Devices Ltd, Cambridge, United Kingdom) was used for the recording of data (area, length, width and perimeter). Moisture content (WC) was determined by oven-drying at 70ºC until constant mass was obtained. Shape factor is defined as the ratio of the actual perimeter (P) to that of a circle with the same area (Pc) (SF=P/P_c ), while specific leaf area (SLA) is obtained using the relation leaf area/dry mass. For histological analysis, leaf cross sections of healthy leaves were prepared for optical microscope examination (Olympus Mod. 1X 51; Olympus Optical Co., GmbH, Hamburg, Germany), using an Olympus Colorview III camera. Leaves were prepared by fixation in FAA (formalin-acetic acid-alcohol, 5:5:90 v/v), for 24 hours. Afterwards, cross sections were placed in 70% ethanol, and dehydration was achieved by immersing them 1 hour, in increasing ethanol concentrations (70%, 80%, 90%, 95% and 100%). Leaf samples were cleared by placing them in xylene, for 1 hour, after which it was embedded overnight in liquid paraffin, using a Leica EG1160 paraffin embedding station. The leaf material was cut using a Leica RM 2135 Rotary Microtome. De-paraffinization was performed using xylene, and hydration achieved by down-grading (100%-70%) ethanol solutions. Staining with toluidine blue (0.1% for 7 minutes) preceded washing with water and new dehydration with ethanol. A last clearing step was performed with xylene, and mounting was completed in Entellan (Merck, Darmstadt, Germany). Biochemical characterization - For the biochemical characterization of the studied plants, totally expanded mature leaves, from ten plants of each species were collected. From these leaves, ten 8 mm (diameter) discs were sampled. The discs were pooled, ground to a fine powder in a mortar with a pestle in the presence of liquid nitrogen and stored at -80 °C until further analysis. Biochemical characterization was performed in six sub-samples of the ground leaves. For the quantification of photosynthetic pigments, chlorophyll a (Cla), b (Clb) and total chlorophyll (Clt), and total carotenoids were spectrophotometrically determined from 80% acetone extracts, using the methods proposed by SESTÁK et al. (1971) and LICHTENTHALER (1987), respectively. The quantification of soluble sugars was performed using the method described by IRIGOYEN et al. (1992). Briefly, ground leaf was extracted with 10 ml of 80% ethanol, at 80ºC, for 1 hour. Afterwards, 0.2 mL of the alcoholic extract and 3 mL of anthrone was added and the mixture was placed in a water bath at 100ºC, for 10 minutes. Following extraction, the solid fractions obtained in the soluble sugar quantification was used for the starch analysis. Extraction was performed using 30% perchloric acid (OSAKI et al., 1991) and quantification followed the anthrone procedure described in the soluble sugars methodology, using also glucose as standard. Total soluble proteins content was quantified as proposed by BRADFORD (1976). Leaf discs were ground in a buffer medium containing 50 mM phosphate buffer (pH 7.8), 0.1 mM ethylenediaminetetraacetic acid (EDTA), 100 mM phenylmethylsulfonyl fluoride (PMSF) and 2% (w/v) polyvinylpyrollidone (PVP), and centrifuged at 22000 g for 30 minutes, at 4 ºC. Absorbance was read at 595 nm, and bovine serum albumin (BSA) was used as a standard. The determination of total phenolics was performed in the same extracts used for the quantification of photosynthetic pigments. The methodology described by SINGLETON and ROSSI (1965) was followed, and quantification was achieved by spectrophotometric readings at 765 nm, using gallic acid as the reference standard, and expressed as mg gallic acid equivalents (GAE’s). Thiobarbituric acid reactive substances determination (TBARS) was evaluated using the method described by BACELAR et al. (2006). Briefly, frozen leaf samples were ground with 2 mL of 20% (w/v) trichloroacetic acid (TCA) using a mortar and pestle. The mixture was centrifuged (3500 g; 20 minutes), and 1 mL of supernatant was combined with 1 mL 20% (w/v) TCA containing 0.5% (w/v) of thiobarbituric acid and 100 µL 4% (w/v) butylated hydroxytoluene (BHT). Thereafter, the mixture was heated at 95ºC for 30 minutes, cooled in an ice bath and again centrifuged at 10,000 X g for 10 minutes. The absorbance of the samples was obtained at 532 nm, whereafter the non-specific absorbance recorded at 600 nm was subtracted. 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